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Home › Publications › OHS Regulation › Guidelines Part 7

Guidelines Part 7

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Guidelines Part 7 - Division 4 - Thermal Exposure

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G7.27(1) Heat exposure - Application

Issued August 1999; Revised January 1, 2005

Section 7.27(1) of the OHS Regulation states:

Sections 7.28 to 7.32 apply to a workplace if

(a) a worker is or may be exposed to thermal conditions which could cause heat stress,

(b) the thermal conditions could result in a worker's core body temperature exceeding 38°C (100°F), or

(c) the thermal conditions are in excess of the levels listed in the screening criteria for heat stress exposure in the heat stress and strain section of the ACGIH Standard for unacclimatized workers.

Here are a few examples of workplaces where the sections on heat exposure may apply:

• Pulp mills (around the recovery boilers, paper machines, and lime kilns)
• Sawmills (around the kilns or burners)
• Smelters
• Cement kilns
• Outdoor work sites during hot weather (road construction and asphalt paving, roofing, tree planting)

For outdoor work areas in B.C., heat stress is normally only of concern during periods of hot weather and during activities such as firefighting unless factors such as high humidity, heavy work load, or excessive radiant heat combine to increase the level of risk for a particular work activity.

G7.27(2) Firefighting

Issued January 1, 2005

Section 7.27(2) of the OHS Regulation states:

Subsection (1) does not apply to firefighting if special provisions satisfactory to the Board are in place to ensure that the firefighter's core body temperature is maintained below 38°C (100°F).

Special provisions related to firefighting that fulfill the intent of this section include:

• Instruction and training
• Work procedures that address both the hazards and necessary controls
• Specialized personal protective equipment

G7.28(1) Exposure limits - Using the ACGIH Standard

Issued August 1999; Revised January 1, 2005; Revised February 12, 2008

Regulatory excerpt
Section 7.28(1) of the OHS Regulation ("Regulation") states:

A worker must not be exposed to levels that exceed those listed in the screening criteria for heat stress exposure in the heat stress and strain section of the ACGIH Standard.

Purpose of guideline
The purpose of this guideline is to explain the use of screening criteria to determine heat stress exposure.

Exposure limits
Table 1 lists values from the 2007 edition of the American Conference of Governmental Industrial Hygienists (ACGIH) publication Threshold Limit Values (TLV^®) and Biological Exposure Indices.

Table 1 : Screening criteria for heat stress exposure (WBGT values in °C)

	TLV®				Action Limit
Work/Recovery cycle	Light	Moderate	Heavy	Very heavy	Light	Moderate	Heavy	Very heavy
75 - 100% work	31	28	-	-	28	25	-	-
50 - 75% work	31	29	27.5	-	28.5	26	24	-
25 - 50% work	32	30	29	28	29.5	27	25.5	24.5
0 - 25% work	32.5	31.5	30.5	30	30	29	28	27

WBGT means the wet bulb globe temperature measured with a black globe thermometer (GT), wet bulb thermometer (WB), and a dry bulb (air) thermometer (DB), and measured according to the following equations:

For indoor or outdoor environments without direct exposure to sunlight,

     WBGT°C = 0.7WB + 0.3GT

For outdoor environments with direct exposure to sunlight,

     WBGT°C = 0.7WB + 0.2GT + 0.1DB     

The WBGT is based on environmental conditions (air temperature, radiant heat, and humidity). Table 1 also considers other criteria based on

• Acclimatization - whether or not workers are acclimatized to heat
• Work demands (metabolic rate category for the work) - light, moderate, heavy, or very heavy
• Approximate proportion of work within an hour — 75 -100% work, 50 - 75% work, etc., with the remaining fraction of the hour allocated to recovery or "rest"

This guideline will help clarify the ACGIH table for heat stress exposure by explaining the various screening criteria and providing formulae for calculating the WBGT where the work demands or work environments vary. Further assistance may be obtained by contacting a WorkSafeBC office.

The values in this table were developed for a traditional work uniform of a long-sleeved shirt and pants. If workers are required to wear clothing that would not fit in this category, then adjustments need to be made to the measured WBGT; see OHS Guideline G7.28(2), Clothing Correction Values before comparing to the heat stress exposure screening criteria. For workers wearing clothing that restricts the movement of air or is impermeable to air or water vapour, the above criteria cannot be used and may necessitate physiological monitoring to ensure adequate protection. See OHS Guideline G7.29-3 for further information.

Work demands
To compare a worker's exposure with the screening criteria, an estimate of the worker's work demands (i.e., metabolic rate) needs to be determined as well as a measurement of the WBGT associated with each task performed during a 1-hour time period.

Four different work demand categories are listed in Table 1: light, moderate, heavy, and very heavy. Table 2 gives examples of activities within each category. The representative metabolic rate in watts for light to very heavy work has been added as this is needed to calculate the work demand when a worker carries out different tasks.

Table 2: Metabolic rate categories and the representative metabolic rate with example activities

Category	Metabolic Rate (W)*	Examples
Rest	115	Sitting
Light	180	Sitting with light manual work with hands or hands/arms, and driving. Standing with some light arm work and occasional walking.
Moderate	300	Sustained moderate hand and arm work, moderate arm and leg work, moderate arm and trunk work, or light pushing and pulling. Normal walking.
Heavy	415	Intense arm and trunk work, carrying, shoveling, manual sawing; pushing and pulling heavy loads; walking at a fast pace.
Very Heavy	520	Very intense activity at fast to maximum pace.

* The effect of body weight on the estimated metabolic rate can be accounted for by multiplying the estimated rate by the ratio of actual body weight divided by 70 kg (154 lb).

Calculations to use if work demands vary
If a worker is assigned different tasks within the hour, it is necessary to determine a time-weighted average (TWA) for the work demands. An acceptable way of doing this is to assign a metabolic rate to each task performed during the averaging period (1 hour), using the values in Table 2, and multiply it by the duration of each task. The product of work demand and duration for each task is then added up, and the sum is divided by the total duration of all tasks performed during the averaging period. The averaging period should be one hour, the same period of time that is used to calculate the time-weighted average WBGT.

The time-weighted average work demand is given by the following formula:

With work demand (TWA) in watts, Table 2 can be used to select the appropriate column (i.e., work demand level: light, moderate, heavy, or very heavy) to use in Table 1. The work demand (TWA) and the WBGT (calculated earlier) are then compared to the heat stress exposure values listed in Table 1.

Proportion of work and recovery
Table 1 gives four work/recovery patterns, and the most appropriate one should be used for comparison with the WBGT calculated earlier. The recovery period percentage does not necessarily mean a complete break from work, but could include "resting" or light tasks such as those listed in Table 2.

Note that the table does not provide exposure values for "heavy" and "very heavy" work demands in a continuous (75 - 100% work) pattern and "very heavy" work demands for a 50 - 75% work pattern. This is because of the high physiological strain associated with "very heavy" work among less fit workers, regardless of WBGT. In such cases, the screening criteria values are not recommended, and a detailed analysis and/or physiological monitoring should be used. (See also OHS Guideline G7.29-3).

Calculations to use if environments vary
If a worker is employed in two or more different work or recovery areas during the hour, a time-weighted average WBGT should be calculated in order to apply the heat stress exposure screening criteria. The time-weighted average is determined by measuring the WBGT for each task performed and multiplying them by the duration of each task. The product of WBGT and duration for each task is then added up, and the sum is divided by the total duration of all tasks performed during the hour.

The time-weighted average WBGT is given by the following formula:

Determining compliance with the exposure levels
Once the time-weighted averages for both workload and WBGT are calculated using the formula above, they are then compared to the levels listed in Table 1. The ACGIH TLV^® represents conditions that acclimatized workers who are healthy, unmedicated, and adequately hydrated may be repeatedly exposed to without adverse health effects. The Action Limit applies similarly for the protection of unacclimatized workers. It also represents conditions that require a heat stress control plan.

For instance, if the calculated time-weighted average for work demands is 415 watts, the work demands are considered "heavy." If the worker is acclimatized, conducting 50 - 75% work and if the WBGT time-weighted average is 27 WBGT°C, then the TLV^® level of 27.5 WBGT°C will not have been exceeded. The Action Limit of 24°C will have been exceeded and an exposure control plan needs to be developed (see OHS Guideline G7.29-5). If the worker is unacclimatized, the work pattern will need to be readjusted (e.g. by reducing the allocation of work in the work/recovery cycle, by increasing the recovery period, or changing to less strenuous tasks until the worker is acclimatized).

G7.28(2) Clothing correction values

Issued January 1, 2005; Revised February 12, 2008

Regulatory excerpt
Section 7.28(2) of the OHS Regulation states:

Clothing corrections must be applied in accordance with the heat stress and strain section of the ACGIH Standard.

Purpose of guideline
The purpose of this guideline is to specify clothing adjustment factors and values for use when calculating heat stress exposure.

Clothing Correction Factors and Values
The body's main heat-removal mechanism is the evaporation of sweat from the skin, so the clothing worn by workers affects the body's ability to remove heat. The heat stress exposure levels listed in the screening criteria - see OHS Guideline G7.28(1) - are for fully clothed workers wearing summer work garments of lightweight pants and long-sleeved shirt. Workers wearing more clothing may experience lessened evaporative and convective cooling and therefore the measured wet bulb globe temperature (WBGT) is to be adjusted. Some suggested clothing adjustment factors from the ACGIH Standard are provided in the following table. The figure in the table is to be added to the WBGT measured in the workplace. Factors for other clothing appearing in the literature can be used in a similar fashion following good professional judgment.

Additions to measured WBGT values (°C) for some clothing ensembles

Clothing type	WBGT addition*
Work clothes (long-sleeved shirt and pants)	0
Cloth (woven material) overalls	0
Double-layer woven clothing	3
SMS polypropylene coveralls	0.5
Polyolefin coveralls	1
Limited-use vapour-barrier coveralls	11

* These values must not be used for completely encapsulating suits, often called Level A clothing. Clothing adjustment factors cannot be added together for multiple layers. The values for coveralls assume that only modesty clothing is worn underneath, not a second layer of clothing.

The ACGIH does not recommend using the WBGT heat stress exposure screening criteria for workers wearing clothing that is impermeable to air or water vapour or multiple layers where no data is available for adjustment. See OHS Guideline G7.29-3 for further information.

G7.29-1 Heat stress assessment

Issued August 1999; Revised January 1, 2005

Section 7.29(1)(a) of the OHS Regulation states:

If a worker is or may be exposed to the conditions specified in section 7.27, the employer must

(a) conduct a heat stress assessment to determine the potential for hazardous exposure of workers, using measures and methods that are acceptable to the Board, and . . .

The first step in a heat stress assessment should be to determine the areas, tasks, or occupations that put workers at risk of heat-related disorders. Factors that should be considered when making this determination include:

• Areas with temperatures above 23°C (summer or winter)
• Areas with high humidity
• Jobs or tasks that require medium to high exertion or strength
• Areas, tasks, or occupations that have been identified through accident investigation reports, first aid treatment record books, and records of injury and disease
• Areas, tasks, or occupations about which employees have expressed concern

Once it is determined which occupations, tasks, or areas should be monitored, the risk of developing a heat-related disorder should be evaluated.

Several different methods of assessing heat stress are available, including:

• Measurement of environmental parameters, such as air temperature, air velocity, air humidity, and infrared radiation (see OHS Guideline G7.29-2 and G7.29-4)
• Direct measurement of body temperature (see OHS Guideline G7.29-3)
• Measurement of other physiological responses, such as heart rate (see OHS Guideline G7.29-3)

Environmental parameters are the most practicable for measuring in the field.

G7.29-2 Environmental parameters

Issued August 1999; Revised January 1, 2005

Section 7.29(1)(a) of the OHS Regulation states:

If a worker is or may be exposed to the conditions specified in section 7.27, the employer must

(a) conduct a heat stress assessment to determine the potential for hazardous exposure of workers, using measures and methods that are acceptable to the Board, and . . .

The most common and widely used heat stress index is the wet bulb globe temperature (WBGT). The WBGT combines the effect of humidity and air velocity (natural wet bulb) ambient air temperature, velocity, and radiant energy (globe temperature), and air temperature (dry bulb temperature) into a single value. The values listed in screening criteria for heat stress exposure are WBGT in °C. (See OHS Guideline G7.28(1) for the table of screening criteria.)

To determine the WBGT, a black globe thermometer, a natural (static) wet bulb thermometer, and a dry bulb thermometer are required. For guidelines on measuring the WBGT, refer to "Temperature Extremes" in the Fundamentals of Industrial Hygiene published by the National Safety Council. Commercial direct-reading monitors are also available that will measure the environmental parameters and directly calculate the WBGT.

Other heat stress indices are available to measure heat stress, including the wet globe temperature (WGT), or Botsball, and ISO 7933 Hot Environments - Analytical Determination and Interpretation of Thermal Stress Using Calculation of Required Sweat Rate. Under certain circumstances, the Botsball may be used instead of the WBGT. For example, a Botsball may be used as a screening tool, or for conditions of moderate radiant heat and humidity such as in general construction work.

Information on the various heat stress indices that are available can be found in such references as:

• NIOSH. 1986. Criteria for a Recommended Standard: Occupational Exposure to Hot Environments. Published by the National Institute for Occupational Safety and Health. Available online: http://www.cdc.gov/niosh/86-113.html
• Barbara A. Plog and Patricia J. Quinlan. 2002. Fundamentals of Industrial Hygiene, 5th edition. Published by the National Safety Council.

For further information regarding measures and methods acceptable to the Board please contact your local WCB office.

G7.29-3 Physiological measures

Issued August 1999; Revised January 1, 2005

Section 7.29(1)(a) of the OHS Regulation states:

If a worker is or may be exposed to the conditions specified in section 7.27, the employer must

(a) conduct a heat stress assessment to determine the potential for hazardous exposure of workers, using measures and methods that are acceptable to the Board…

In some occupations or work environments, workers must wear clothing that is either vapour or air impervious/impermeable. Examples of such clothing are full-body chemical protective equipment (HAZMAT suit) and firefighting turnout gear.

In these particular cases, the use of an environmental measure such as the wet bulb globe temperature (WBGT) will not be indicative of actual exposure conditions experienced by the worker wearing such protective equipment. Instead, the worker should be monitored to ensure that safe body temperatures are not exceeded. The body functions best when the core body temperature is within a range of 36°C to 38°C.

There are two physiological parameters that can be used to monitor a worker's state of heat stress: measurement of the core body temperature and heart rate.

Core body temperature can be measured either directly using rectal temperature or approximated by measuring oral or tympanic (ear-drum/canal) temperatures. Oral temperatures are determined by measuring temperature at the base of the tongue. The worker must not drink or eat anything cold or hot for at least 15 minutes before measurement. The thermometer must be inserted under the tongue, as far as possible, for about 5 minutes, and the mouth must be kept closed as much as possible. Oral temperature is approximately 0.4°C lower than rectal temperature.

The recovery heart rate during rest periods following a work cycle in a hot environment is a measure that can be used to monitor heat stress. There are two models for recovery heart rate.

The first (Brouha) recommends a heart rate criterion level of 110 beats per minute during the first minute of a rest period after work in a hot environment, followed by a reduction in heart rate of 10 beats per minute by the end of the third minute of rest. Levels above these values are indicative of exposure to a heat stress environment.

The second model (Fuller and Smith) recommends that the heart rate in the third minute of a rest period after work in a hot environment should not exceed 90 beats per minute.

Further information on physiological monitoring can be obtained from the 1986 NIOSH document Criteria for a Recommended Standard: Occupational Exposure to Hot Environments available on the NIOSH web site: http://www.cdc.gov/niosh/86-113.html or contact an occupational hygiene officer at your local WCB office.

G7.29-4 Heat stress assessment using a dry bulb thermometer or Humidex index

Issued August 1999; Revised January 1, 2005; Revised February 12, 2008

Regulatory excerpt
Section 7.29(1)(a) of the OHS Regulation ("Regulation") states:

(1) If a worker is or may be exposed to the conditions specified in section 7.27, the employer must

(a) conduct a heat stress assessment to determine the potential for hazardous exposure of workers, using measures and methods that are acceptable to the Board, and ...

Purpose of guideline
The purpose of this guideline is to outline the circumstances under which a heat stress assessment may be done using a Humidex-based method or a dry bulb thermometer, and describes procedures for using the Humidex-based method.

Background information
WorkSafeBC recommends taking measurements of the wet bulb globe temperature (WBGT) to measure heat stress, as described in OHS Guideline G7.28(1). This method requires complex instrumentation and training in use of the equipment. The use of other heat stress indices can simplify measurement in certain circumstances. Simplified measurements may be helpful in workplaces where heat stress is a seasonal concern in periods of hot weather conditions. See OHS Guideline G7.29-2 for references on various heat stress indices.

The dry bulb thermometer method and the Occupational Health Clinics for Ontario Workers Inc. (OHCOW) Humidex Based Heat Response Plan (Humidex method) are tools that help assess heat stress for the purpose of managing heat stress and strain in the workplace. These methods are not applicable in all circumstances and/or workplaces. Further, these methods do not replace use of the WBGT for assessing compliance with the exposure limits established in section 7.28 of the Regulation. (Caution: never ignore symptoms of heat strain even if measurements meet standards.)

Dry bulb thermometer or Humidex-based methods may only be used in situations where workers are not exposed to

• Sources of direct heat (infrared radiation) emanating from industrial equipment such as boilers, furnaces, steam lines, molten metal, or from other hot surfaces. Workplaces with significant radiant-heat load from process-related heat or where workers have experienced heat-related illness should measure the WBGT.
• High humidity levels produced by industrial equipment such as a pulp or paper machine in a pulp & paper mill, or to open sources of high temperature steam.

Humidex-based or dry bulb thermometer methods can be effective for workers wearing clothing that allows effective evaporative heat loss; for workers wearing impervious or semi-impervious clothing, heat stress management should include monitoring of vital signs (see ACGIH TLV^® for Heat Stress, section 4).

In essence, these alternate methods are applicable to addressing the issue of heat stress in office buildings, retail facilities, health care facilities, hospitality industry, warehouses, or working outdoors, where a worker is not exposed to process-related heat or to industrially-produced high humidity levels.

Dry bulb method
Air temperature determined using a normal dry bulb thermometer will be considered an acceptable measuring standard under section 7.29 of the Regulation if all of the following conditions apply

1. The air temperature measured in the immediate area where the work is taking place does not exceed 35°C (95°F). It is not sufficient to use a temperature level reported from another location, such as over the local radio station, or a reading taken at some distant location on the work site. Reflection off of walls or disruptions in wind flow in the immediate area where the work is being done may cause the temperature to vary significantly from the "general temperature" for the local area.
2. Where sources of radiant heat do not add significantly to the heat load. For example, equipment (an operating boiler or steam lines) and other hot surfaces (a tar and gravel roof or black asphalt pavement being heated by the sun) may be significant sources of radiant heat. A normal dry bulb thermometer does not measure infrared radiation, which is the source of radiant heat.
3. The work being done, if classified as "heavy" as described in Table 2 of OHS Guideline G7.28(1), does not exceed 2 hours in duration
4. Worker(s) are not wearing impervious or semi-impervious protective clothing.
5. If the air temperature measured is 30°C (86°F) or higher, an exposure control plan, as outlined below, is implemented unless the heat exposure is determined through use of the WBGT method to be below the Action Levels listed for unacclimatized workers in the screening criteria for heat stress exposure in the heat stress and strain section of the ACGIH Standard.

If any of the above conditions are not met, more precise measurements such as WBGT or Botsball temperature plus estimates of workload are required to determine the risk of heat stress in order to achieve compliance with section 7.29 of the Regulation.

Exposure control plan (ECP) requirements for dry bulb temperature assessments
If the above limiting conditions are met, and the heat stress assessment is being done using only a normal dry bulb thermometer, and the measured temperature equals or exceeds 30°C (86°F), an ECP for heat stress is to be implemented.

At a minimum, the heat stress ECP is to include

• Worker education and training as noted below
• Continuous availability of cool potable water close to the work area (see section 7.31 of the Regulation)
• Personal monitoring of heart rate to confirm the effectiveness of the work/recovery schedule (see details outlined below)
• Continuous supervision by a person knowledgeable in heat stress symptoms and control program requirements

Under this provision, workers in a heat stress environment are to be provided with information about

• Heat-related disorders, associated symptoms and the need to report their symptoms
• Factors increasing susceptibility to heat-related disorders
• Heat stress implications for any existing medical conditions and treatment, such as sleep deprivation, dehydration, diabetes, hyperthyroidism, and some medications
• Safe work procedures for work in heat stress areas, including work/recovery schedules, the importance of fluid loading and replacement, and the immediate reporting of symptoms of heat-related disorders to the supervisor
• Any environmental or personal monitoring programs used on-site
• Safe use of protective clothing and equipment, if required

As part of this provision, workers should check their "resting heart rate" prior to starting work in the area, and again before and after rest periods. At the beginning of the recovery period, the heart rate should not exceed 110 beats per minute. If it does, the work period should be shortened by one-third while maintaining the same rest period. At the end of the rest period, the pulse should be within 10 beats per minute of the resting heart rate before resuming work. Note that heart rate is only one symptom of heat stress. Workers and supervisors need to remain vigilant for other signs of heat-related illness.

Hot conditions and workload or personal monitoring may indicate that additional rest breaks are needed in the work rest cycle. Rest periods do not always require a change in location from the work environment. Rest periods do require that workers move away from direct sunlight or other sources of radiant heat and that they change to less strenuous tasks to reduce the build-up of body heat.

Humidex Method
The Humidex Based Heat Response Plan is a simplified method of protecting workers from heat stress, (developed by the Occupational Health Clinics for Ontario Workers (OHCOW)). The method is based on the American Conference of Governmental Industrial Hygienists (ACGIH) heat stress/strain TLVs^® (Threshold Limit Values) and is a translation of wet bulb globe temperatures (WBGT) into Humidex values. Other factors - air movement, workload, radiant heat sources, and acclimatization - also need to be considered when assessing heat stress.

Humidex values are obtained by measuring temperature (dry bulb) and relative humidity and factoring them into the Humidex table below (Table 1). For example the Humidex value for a temperature of 37°C (read across from the left side of the Table) and a relative humidity of 50 percent (read down from the top of the Table) is 49°C. Temperature and relative humidity can be measured by a digital hygrometer (available at most hardware stores) or a sling psychrometer (a wet/dry bulb thermometer for determining relative humidity). It is important that a reading be taken at the actual workplace as Humidex values can vary substantially from location to location.

Table 1: Humidex Table

The following must also be considered (added) when calculating a Humidex value:

• The Humidex method assumes that workers are wearing regular summer clothing (light shirt, pants, underwear, socks and shoes). If workers wear coveralls (e.g., cotton coveralls) over summer clothes, then 5°C should be added to the workplace Humidex value. Gloves and/or hard hat would each add 1°C and an apron (or vest) would add 2°C to the Humidex value. For workers who wear encapsulating suits, do not use the Humidex method.
• To adjust for radiant heat in direct sunlight (between 10 am and 4 pm), add 2 - 3°C to the Humidex value (pro-rate according to percentage cloud cover).
• For indoor radiant heat exposures, use training, knowledge, and experience to adjust the 2 - 3°C sunlight correction factor by estimating whether the exposure is more or less than the heat exposure to direct sunlight. Workplaces with significant process-related heat load (e.g. from boilers, furnaces, steam lines, etc.) should measure the WBGT.
• Humidex values should be measured at several locations in the work area (safe work procedures should be based on the highest reading).
• Do not base Humidex values on weather station or media reports. Use measurements taken at the worksite.
• Measurement should be recorded hourly if the Humidex is above 30°C.
• Never ignore anyone's symptoms regardless of the measurements.

In order to determine the procedures to be followed to protect workers from heat stress, the calculated Humidex value must then be compared to the Humidex guidelines in the Humidex Heat Response Plan table (Table 2). The response (Humidex 1 or Humidex 2) depends on the amount of physical work being done and the level of acclimatization of the workers.

Humidex 1 - corresponds to the ACGIH Action Limit and applies to moderate work loads (e.g., pushing and lifting) for unacclimatized workers, or heavy work loads (e.g., shoveling sand) for workers acclimatized to heat (see also OHS Guideline G7.28(1)).
Humidex 2 - corresponds to the ACGIH TLV^® and applies to moderate work for acclimatized workers or light work for unacclimatized workers.

Note: An unacclimatized worker is a worker who is not accustomed to working in a hot environment or who has been out of a hot environment for seven consecutive days. It may take several days for workers to become acclimatized.

 

Table 2: Humidex Based Heat Response Plan

Humidex 1 Moderate unacclimatized & Heavy acclimatized	Response	Humidex 2 Moderate acclimatized & Light unacclimatized
25 - 29	Supply water to workers on an "as needed" basis	32 - 35
30 - 33	Post Heat Stress Alert notice; encourage workers to drink extra water; start recording hourly temperature and relative humidity	36 - 39
34 - 37	Post Heat Stress Warning notice; notify workers that they need to drink extra water; ensure workers are trained to recognize symptoms	40 - 42
38 - 39	Work with 15 minutes relief per hour can continue; provide adequate cool (10-15°C ) water; at least 1 cup (240 mL) of water every 20 minutes. Worker with symptoms should seek medical attention	43 - 44
40 - 41	Work with 30 minutes relief per hour can continue in addition to the provisions listed previously	45 - 46*
42 - 44	If feasible, work with 45 minutes relief per hour can continue in addition to the provisions listed above	47 - 49*
45* or over	Only medically supervised work can continue	50* or over

* at Humidex exposures above 45, heat stress should be managed as per the ACGIH TLV^®. The above administrative control measures do not preclude using other means to reduce excessive heat exposures, such as providing additional air conditioners or fans for spot cooling. In fact, engineering controls are the most effective means to control heat stress and should be considered first and in conjunction with the above steps as part of the heat stress ECP. For more examples of control measures, refer to WorkSafeBC publication Preventing Heat Stress at Work available at http://www.worksafebc.com/publications/health_and_safety/by_topic/assets/pdf/heat_stress.pdf.

The Humidex Based Heat Response Plan is also available on the OHCOW website at http://www.ohcow.on.ca/menuweb/hhrplan.pdf. An alternative way to determine the Humidex value is to use the "calculator" on the OHCOW website (http://www.ohcow.on.ca/menuweb/heat_stress_calculator.htm). Enter the dry bulb temperature and relative humidity level in order to calculate the Humidex value.

Heat Stress ECP
A heat stress assessment and ECP based on the Humidex method consists of the following steps:

1. Assign roles and responsibilities in the plan.
2. Train workers in early signs and symptoms of heat stress.
3. Select representative measurement locations in the workplace that will be monitored for temperature and relative humidity.
4. Determine the Humidex value, including the adjustments for clothing and radiant heat.
5. Compare the Humidex value to the appropriate criteria according to work demand and worker condition (Humidex 1 or Humidex 2).
6. Select and apply the control measures listed.
7. Maintain records.
8. Monitor the effectiveness of control measures. Regardless of Humidex values, individual symptoms must never be ignored.

If the above conditions for using the Humidex method are not met, WBGT measurements must be made plus estimates of workload are required to determine the risk of heat stress in order to achieve compliance with section 7.28 of the Regulation. Physiological monitoring may also be required.

Humidex Calculation Example # 1
This example concerns a worker performing roadway repairs in the B.C. Interior, in July. The weather is sunny (no cloud cover) and the temperature and relative humidity are 32°C and 30%, respectively.

The Humidex value from Table 1 is 34°C.

As the worker is wearing coveralls and gloves (as well as other safety equipment, e.g., work boots and hard hat), a value of 5°C (for the coveralls) and 1°C (for the gloves and/or hardhat) will have to be added. Another 3°C are added to adjust for radiant heat in direct sunlight (the worker is exposed to direct sun on the roadway). The final calculation for Humidex becomes: 34 + 5 + 1 + 3 = 43 degrees Celsius.

The Humidex value must then be compared to the ranges in Table 2 (Humidex 1 or Humidex 2), depending on whether or not the worker is acclimatized. If we assume the worker is acclimatized and performing heavy work (e.g., shoveling gravel), then Humidex 1 applies.

The recommended response plan would be Humidex 1 (42 to 44°C) and the following control measures would apply:

• Ensure workers are trained to recognize symptoms of heat stress.
• Post "Heat Stress Alert" notices.
• Supply water to the worker as needed - at least 1 cup (240 ml) of 10 to 15°C water every 20 minutes.
• Work with at least 30 minutes relief per hour, however, if feasible work with 45 minutes relief per hour.
• Record temperature and humidity on an hourly basis.

Humidex Calculation Example #2
This example concerns a worker in a commercial office building, in August. The building is not air-conditioned and the interior temperature and relative humidity are 28°C and 30%, respectively.

The Humidex value from Table 1 is 29°C.

The Humidex value must then be compared to the ranges in Table 2 (Humidex 1 or Humidex 2), depending on whether or not the worker is acclimatized. If we assume the worker is performing light work (which is typical in an office environment), then neither Humidex applies (there is no "Light" work category for Humidex 1 and the "Light unacclimatized" ranges for Humidex 2 are all greater than 29°C) and there is no heat stress issue.

In this example, the temperature of the indoor air and the comfort of the occupants are also addressed in Regulation section 4.80.

G7.29-5 Exposure control plan

Issued August 1999; Revised January 1, 2005

Section 7.29(1)(b) of the OHS Regulation states:

If a worker is or may be exposed to the conditions specified in section 7.27, the employer must . . .

(b) develop and implement a heat stress exposure control plan meeting the requirements of section 5.54(2).

For the general requirements of an exposure control plan, refer to section 5.54(2) and OHS Guideline G5.54-1. Some specific elements of the exposure control plan, as they relate to heat stress, are described below.

General duties and responsibilities
The statement of responsibilities should include roles for both the employer and workers. It should incorporate the following:

• Employer responsibilities:
  • identify and assess areas, tasks, and occupations where there is the potential for heat stress
  • implement and/or provide controls (engineering, administrative, or personal protective equipment) to minimize heat stress
  • provide training and education regarding heat stress, including early signs and symptoms of heat-related disorders
• Worker responsibilities:
  • participate in environmental monitoring program to assess worker exposure to conditions that could cause heat stress,
  • adhere to all control measures or work procedures that have been designed and implemented to reduce exposure to conditions that could cause heat stress
  • leave hot environments if signs or symptoms of a heat-related disorder appear

Risk identification, assessment, and control
This element should state the following:

• How the employer will determine those workers who may be at risk of heat-related disorders
• Who will conduct the heat stress assessments (if specific individuals are not identified, this element should contain easy-to-read instructions outlining how to conduct a heat stress assessment and the methods of control that should be used)
• How the heat stress hazard will be assessed (such as the measurement indices that will be used)
• What controls will be used to eliminate or minimize worker exposure to conditions that could cause heat stress, as well as when and how the controls will be implemented

Refer to OHS Guideline G7.29-1 for guidance on conducting a heat assessment and to OHS Guidelines G7.30-1 through G7.30-3 for information on controlling risk.

Education and training
This element should contain training and education, initial and ongoing, that will be provided to all workers who work in areas, tasks, or occupations where there is a reasonable likelihood of heat stress. The training and education material provided to workers who have not previously worked in a heat stress environment should include the following information:

• Heat-related disorders (heat cramps, heat exhaustion, and heat stroke)
• Relevant signs and symptoms of heat-related disorders
• Predisposing factors for heat-related disorders include the following:
  • lack of acclimatization
  • poor physical fitness
  • obesity
  • increased age
  • dehydration
  • pre-existing medical conditions and treatment (for example, diabetes or hyperthyroidism)
  • short-term disorders and minor illnesses (for example, cold, flu, or diarrhea)
  • chronic skin disorders (for example, rashes or dermatitis)
  • use of medication that may inhibit sweating, reduce blood flow or cause dehydration (for example antihistamines)
  • alcohol abuse and recreational drugs
  • previous heat illness
• Potential health effects of excessive heat stress
• First aid procedures
• Safe work procedures and proper precautions for work in heat stress areas, including the importance of fluid replacement and of immediately reporting the development of signs or symptoms of heat-related disorders to the employer
• Purpose and description of the environmental monitoring program, as well as the benefits to the worker of participating in these programs
• Proper use of protective clothing and equipment, if required

For those workers exposed to environments that could cause heat stress, provide refresher training and education to ensure that workers remain knowledgeable about the above-mentioned items. It is recommended that continuing education be provided at least annually.

For further information, consult WCB booklet Preventing Heat Stress at Work, on the WCB web site at www.WorkSafebc.com.

Written procedures
The employer should prepare written procedures on assessing heat stress, as well as on using control measures to minimize heat stress (for example, positioning and use of supplemental fans for cooling, using and caring for radiant heat reflective clothing, or using vortex or ice-pack cooling suits).

G7.30-1 Engineering controls

Issued August 1999; Revised January 1, 2005

Section 7.30(1) of the OHS Regulation states:

If a worker is or may be exposed to the conditions specified in section 7.27, the employer must implement engineering controls to reduce the exposure of workers to levels below those listed in the screening criteria for heat stress exposure in the heat stress and strain section of the ACGIH Standard.

Section 7.30 of the OHS Regulation requires an employer to reduce the exposure of workers to heat stress conditions using a hierarchy of control methods: engineering controls, followed by administrative controls and, as a last resort, personal protective equipment.

Engineering controls are the most effective means of reducing excessive exposure conditions that could cause heat stress. Examples of engineered approaches to reduce heat exposure include, but are not limited to, the following:

• Reducing metabolic heat production. Automation and mechanization of tasks can minimize the need for heavy physical work and the resulting buildup of body heat.
• Reducing the radiant heat emission from hot surfaces. Covering hot surfaces with sheets of low-emissivity material, such as aluminum or other shielding material, reduces the amount of heat radiated into the workplace.
• Insulating hot surfaces. Insulation reduces the heat exchange between the source of heat and the work environment.
• Shielding. Shields stop radiated heat from reaching workstations. Stainless steel, aluminum, and other bright metal surfaces reflect heat back towards the source. Absorbent shields, such as water-cooled jackets made of black-surfaced aluminum, can effectively carry away heat.
• Ventilation and air-conditioning. Ventilation, localized air-conditioning, and cooled observation booths are commonly used to provide cool working conditions.
• Spot cooling. Freestanding fans may be used to provide localized air movement at work locations. Typically, an increased rate of air movement over the body will cause increased cooling due to the evaporation of sweat, although this will depend on humidity. (Take care that spot cooling or blowers do not interfere with ventilation systems used to control toxic chemical agents.)
• Reducing the humidity. Air-conditioning and dehumidification, as well as elimination of open water baths, drains, and leaky steam valves, all help to reduce humidity.

G7.30-2 Administrative controls

Issued August 1999; Revised January 1, 2005

Section 7.30(2)(a) of the OHS Regulation states:

(2) If the action described in subsection (1) is not practicable, the employer must reduce the exposure of workers to levels below those listed in the screening criteria for heat stress exposure in the heat stress and strain section of the ACGIH Standard by providing

(a) administrative controls, such as a work rest cycle, acceptable to the Board or . . .

If engineering controls are not practicable, section 7.30(2)(a) permits the use of administrative controls, such as an acceptable work rest cycle, to reduce the exposure of workers to below the screening criteria levels.

Several administrative controls that are commonly used to reduce worker exposure to heat stress are described below.

• Fluid replacement and work practices. Section 7.31 of the OHS Regulation requires employers to provide and maintain an adequate supply of cool potable water (10-15°C) close to the work area for the use of a heat exposed worker who is or may be exposed to the conditions specified in section 7.27. Workers should be encouraged to drink small amounts frequently, such as one cup every 20 minutes.
• Work rest cycles. A work rest cycle refers to the period a worker spends working in a hot or strenuous environment and the time spent in a rest or recovery area.
• Acclimatization. The body will adapt to working in hot conditions if it is allowed sufficient time. This physiological process is referred to as acclimatization and can usually be induced in 4 to 7 days of exposure to a hot environment.
• Scheduling and organization of work. There are several ways to organize and to schedule tasks so as to minimize the length of time and temperatures to which workers may be exposed. For example:
  • When possible, schedule hot tasks for the cooler part of the day (early morning, late afternoon, or night shift).
  • Schedule routine maintenance and repair work in hot areas for cooler seasons of the year.
  • Adjust schedules where possible so that hot operations are not performed at the same time and place as other operations that require the presence of workers (for example, do not schedule maintenance cleanup while tapping a furnace).
  • Add extra personnel to reduce exposure time for each member of the crew.
  • Where practical, allow workers to set their own pace of work.
  • If weather forecasts predict very hot conditions, postpone tasks that are not urgent until the hot spell is over.
• Signage. Heat stress hazard warning signs may be posted in indoor work areas where the heat exposure limits could be exceeded if a worker was continuously exposed to heat.

G7.30-3 Personal protective equipment

Issued August 1999; Revised January 1, 2005

Section 7.30(2)(b) of the OHS Regulation states:

(2) If the action described in subsection (1) is not practicable, the employer must reduce the exposure of workers to levels below those listed in the screening criteria for heat stress exposure in the heat stress and strain section of the ACGIH Standard by providing . . .

(b) personal protective equipment, if the equipment provides equally effective protection as administrative controls.

Where it provides equally effective protection and the use of engineering or administrative controls is not practicable, the use of personal protective equipment is permitted under section 7.30(2)(b).

There are two main types of heat-protective clothing available:

• Anti-radiant heat or reflective clothing. This type of clothing may be necessary when there is excessive radiant heat from a hot surface that cannot otherwise be covered or shielded. This clothing is available in different forms, varying from aprons and jackets to suits that will completely enclose the worker from neck to feet. This type of clothing protects only against radiant heat and provides little or no protection from high air temperatures unless auxiliary cooling is used underneath the clothing.
• Temperature-controlled suits. This type of clothing provides auxiliary cooling of the body while the worker is in the heat stress environment. There are several different types of temperature-controlled suits commercially available, each using a different method of cooling:
  • ice pack vests
  • wetted overclothing such as terry cloth coveralls or two-piece, whole-body cotton suits
  • water-cooled suits such as hoods, vests, and "long-johns" offering partial or complete body cooling
  • air-cooled suits

G7.33-1 Cold exposure - Application

Issued August 1999; Revised January 1, 2005

Section 7.33 of the OHS Regulation states:

Sections 7.34 to 7.38 apply to a workplace if a worker is or may be exposed to

(a) thermal conditions that could cause cold stress or injury,

(b) thermal conditions that could cause a worker's core body temperature to fall below 36°C (96.8°F), or

(c) thermal conditions that are below the levels classified as "little danger" to workers in the criteria for the cooling power of wind on exposed flesh in the cold stress section of the ACGIH Standard.

The sections on cold exposure apply to work environments where workers may be exposed to either artificial or natural cold. Examples of artificially cold workplaces include cold storage rooms, freezers, and refrigerated transportation units. Examples of industries where workers may be exposed to natural cold include fishing, forestry, construction, and the petroleum industry.

In the context of these sections, exposure is taken to mean exposure to cold air or water either as part of routine work procedures or as a result of accidental or an unplanned event. Examples of accidental or unplanned events include a worker falling into water such as from a boat or breaking through ice (cold water immersion) or a worker becoming stranded outdoors in the cold.

Some examples of cold-related injuries include frostbite, frostnip, trenchfoot, and Raynaud's disorder.

G7.33-2 Cooling power of wind (imperial units)

Issued January 1, 2005

Section 7.33(c) of the OHS Regulation states:

Sections 7.34 to 7.38 apply to a workplace if a worker is or may be exposed to . . .

(c) thermal conditions that are below the levels classified as "little danger" to workers in the criteria for the cooling power of wind on exposed flesh in the cold stress section of the ACGIH Standard.

The ACGIH criteria, in the Fahrenheit scale, are listed in the following table as it appears in "Cold Stress" of Threshold Limit Values and Biological Exposure Indices (the ACGIH Standard). See OHS Guideline G7.33-3 for a table in metric units. The table shows the cooling power of wind on exposed flesh. If there is a wind, use the wind speed in the first column and the actual temperature across the top to find what the equivalent temperature would be under calm conditions.

G7.33-3 Cooling power of wind (metric units)

Issued January 1, 2005

Section 7.33(c) of the OHS Regulation states:

Sections 7.34 to 7.38 apply to a workplace if a worker is or may be exposed to . . .

(c) thermal conditions are below the levels classified as "little danger" to workers in the criteria for the cooling power of wind on exposed flesh in the cold stress section of the ACGIH Standard.

The ACGIH Standard provides values for the cooling power of wind on exposed flesh in the Fahrenheit scale. The following table has the same information, expressed in degrees Celsius and in km/h. It is organized for actual temperature to decrease by intervals of 5°C, resulting in an additional column. The table shows the cooling power of wind on exposed flesh. If there is a wind, use the wind speed in the first column and the actual temperature across the top to find what the equivalent temperature would be under calm conditions.

G7.34-1 Cold stress assessment

Issued August 1999; Revised January 1, 2005

Section 7.34(a) of the OHS Regulation states:

If a worker is or may be exposed to conditions specified in section 7.33, the employer must

(a) conduct a cold stress assessment to determine the potential for hazardous exposure of workers, using measures and methods that are acceptable to the Board, and . . .

Section 7.34(a) of the OHS Regulation requires that a cold stress assessment be conducted if a worker is or may be exposed to conditions which could cause cold stress or injury, or could cause a worker's core body temperature to fall below 36°C (96.8°F), or fall below the "little danger" levels in the ACGIH table (see OHS Guidelines G7.33-2 and G7.33-3). Part of the cold stress assessment for hazardous exposure should include the potential for unplanned exposure.

The first step in a cold stress assessment is to determine the areas, occupations, or tasks that place workers at risk of hypothermia or cold-related injuries. Consider factors such as the following:

• Areas with an equivalent chill temperature below -7°C (see below)
• Fine dexterity tasks that require work with bare hands
• Contact with metal surfaces or use of evaporative liquids (gasoline, alcohol, or cleaning liquids)
• Working on or near bodies of water
• Areas or occupations that have been identified through accident investigation reports, first aid treatment record books, and records of injury and disease
• Areas or occupations about which employees have expressed concern

Once the areas, occupations, or tasks that should be monitored are determined, the risk of developing hypothermia or a cold-related injury should then be evaluated.

A cold stress assessment should include determining the air temperature and wind speed (to determine the "equivalent wind chill temperature"). This information is available by:

• Obtaining weather, temperature, and wind information from the local weather office (such as from Environment Canada) if there is a monitoring station close to the area in which the work is to be conducted
• Taking a direct measurement of the ambient air temperature using a dry bulb thermometer (or electronic equivalent) and a direct reading of the wind velocity in km/h (or metres/sec) using a velometer, hot-wire thermometer, heated thermocouple, thermistor, or a thermocouple anemometer. Most air velocity instruments also provide a direct readout of air temperature.

Wind chill is a concern when the equivalent chill temperature is less than -7°C. From the metric table in OHS Guideline G7.33-3, the conditions when this occurs are:

• The air is calm and the temperature falls below -7°C
• The wind speed is 8 km/h or greater and the air temperature is -5°C
• The wind speed is 16 km/h or greater and the air temperature is 0°C
• The wind speed is 32 km/h or greater and the air temperature is 5°C

As part of the risk assessment, the potential for worker exposure to artificially generated air velocities should also be considered, for example when working in walk-in refrigerators and freezers, when riding all-terrain vehicles or snowmobiles, or when exposed to helicopter rotor downwash.

A general assessment of contact cooling for exposed skin, particularly the hands, should consider the following when workers are in contact with metal:

• Below 15°C - Prolonged contact may impair dexterity.
• Below 7°C - Prolonged contact may induce numbness.
• Below 0°C - Prolonged contact may induce frostnip or frostbite.
• Below -7°C - Brief contact with may induce frostnip or frostbite.

For materials other than metal, such as plastics and wood, the temperatures will be lower than those noted above since they are less conductive than metal. Any contact with liquids at subzero temperature is also of concern, particularly with cryogenic "fluids" (super-cooled liquefied gases).

Workers should be provided with gloves or other method of warming the hands when the air temperature is below:

• 16°C for sedentary work
• 4°C for light work
• -7°C for moderate work

G7.34-2 Conversion

Issued January 1, 2005

Temperature in degrees Fahrenheit can be converted to degrees Celsius using the following formula.

°Celsius = 5/9 x (°Farenheit - 32)

Wind velocity in miles per hour (mph) can be converted to kilometres per hour (km/h) using the following formula.

km/h = mph x 1.61

G7.34-3 Exposure control plan

Issued January 1, 2005

Section 7.34(b) of the OHS Regulation states:

If a worker is or may be exposed to conditions specified in section 7.33, the employer must . . .
(b) develop and implement a cold exposure control plan meeting the requirements of section 5.54(2).

For the general requirements of an exposure control plan, refer to section 5.54(2) and OHS Guideline G5.54-1. Some specific components of the exposure control plan, as they relate to education and training of workers, are described below.

Education and training
This element should contain initial and ongoing training and education that will be provided to all workers who work in areas where there is a reasonable likelihood of exposure to conditions that could cause cold stress. The training and education material provided to workers who have not previously worked in a cold stress environment should include the following information:

• Recognition of the signs and symptoms of impending hypothermia or excessive cooling of the body even when shivering does not occur
• Recognition of impending frostbite
• Proper re-warming procedures and appropriate first aid treatment
• Proper use of clothing
• Proper eating and drinking practices
• Safe work practices appropriate to the work that is to be performed

For those workers exposed to cold-stress environments, provide refresher training and education to ensure that workers remain knowledgeable about the above-mentioned items. It is recommended that continuing education be provided at least annually.

For further information, consult the WCB publication Hypothermia, on the WCB web site at www.WorkSafebc.com.

G7.35-1 Engineering controls

Issued January 1, 2005

Section 7.35(1) of the OHS Regulation states:

If a worker is or may be exposed to the conditions specified in section 7.33, the employer must implement effective engineering controls to reduce the exposure hazard to levels above those classified as "little danger" to workers in the criteria for the cooling power of wind on exposed flesh in the cold stress section of the ACGIH Standard.

Section 7.35 of the OHS Regulation requires an employer to reduce the exposure hazard of workers to thermal conditions that could cause cold stress or injury using a hierarchy of control methods: engineering controls, followed by administrative controls and, as a last resort, personal protective equipment.

Here are some examples of engineering controls to reduce cold exposure:

• Isolate the worker from the environment, where possible.
• Use local heating for the body and especially bare hands (when fine work is required). This may include the use of warm air jets, radiant heaters, or contact warming plates.
• Provide barricades or other structures to block air or reduce air velocities at the work location.
• Provide heated metal tools and equipment handles or cover them with thermal insulating materials.
• Use machine controls and tools designed so that workers do not have to remove mittens or gloves to use them.

G7.35-2 Administrative controls

Issued January 1, 2005

Section 7.35(2) of the OHS Regulation states:

If the action described in subsection (1) is not practicable, the employer must reduce the exposure hazard by providing
(a) effective administrative controls, or . . .

If engineering controls are not practicable, section 7.35(2)(a) permits the use of effective administrative controls to reduce the exposure hazard of workers to thermal conditions that could cause cold stress or injury.

Several administrative controls that are commonly used to reduce worker exposure to cold stress are described below:

• Work/warm-up schedules. A work/warm-up schedule refers to the period a worker spends working in a cold environment and the time spent in a warm area. See OHS Guideline G7.35-3 for sample schedules.
• Scheduling and organization of work. There are several ways to organize and to schedule tasks so as to minimize the length of time of exposure and to maximize the temperatures to which workers may be exposed. For example:
  • When possible, schedule tasks for the warmest part of the day or when the wind is the most calm.
  • Schedule routine maintenance and repair work for warmer seasons of the year.
  • Postpone non-urgent tasks when equivalent chill temperatures are in the "great danger" portion of the "Cooling Power of Wind" ACGIH table provided in OHS Guideline G7.33-3.
  • Take the equivalent chill temperature into account when planning or scheduling work activities.
• Fluid replacement and diet. An ample supply of warm drinks or soup should be available, and workers should be encouraged to drink them in order to replace fluids lost through breathing and perspiration. Workers should restrict their intake of coffee because of diuretic and circulatory effects. A diet high in fats and carbohydrates may help to maintain body temperature.

G7.35-3 Work/warm-up schedule for a 4-hour shift

Issued January 1, 2005

Section 7.35(2)(a) of the OHS Regulation states:

If the action described in subsection (1) is not practicable, the employer must reduce the exposure hazard by providing
(a) effective administrative controls . . .

A work/warm-up schedule is an example of an administrative control. The ACGIH Standard contains a work/warm-up schedule for a 4-hour shift for workers who are properly clothed. This schedule is acceptable to the Board. Values in the ACGIH table have been converted to metric units in the table below.

Work/warm-up schedule for a 4-hour shift (PDF 33 KB)

G7.35-4 Personal protective equipment

Issued January 1, 2005

Section 7.35(2)(b) of the OHS Regulation states:

If the action described in subsection (1) is not practicable, the employer must reduce the exposure hazard by providing . . .

(b) personal protective equipment, if the equipment provides protection equally effective as administrative controls.

Workers who are at risk of exposure to thermal conditions that could cause cold stress or injury due to unplanned or accidental events should be provided with clothing and equipment sufficient to permit survival from the natural elements until the worker can be removed from the exposure.

As a minimum, a worker should be provided with the following:

• Additional clothing selected in accordance with the anticipated overnight low temperatures for the region in which work or travel is conducted
• A sleeping bag rated for the anticipated overnight low temperatures for the region in which work or travel is conducted
• Survival equipment that will allow a worker to survive the natural elements until rescued

Here are some typical items that should be included in a survival kit:

GENERAL:	SIGNAL:
1 - backpack with pockets	1 - mini-flashlight and batteries
1 - 10 ft x 12 ft plastic tarp	1 - compass
1 - 5 ft x 6 ft polar fleece blanket	1 - survival whistle
2 - tarp straps	1 - set of flares
	1 - handheld flare launcher
COOKING:
2 - large stainless steel cups	OTHER:
2 - sets of cutlery	2 - toilet tissue packets
1 - survival stove	1 - 50 foot parachute cord
1 - 500 mL water bottle	1 - sheathed knife
	1 - tube of lip balm and/or sunscreen
FOOD:	1 - container of insect repellent
4 - instant soup mix	1 - small folding saw
10 - tea bags	4 - garbage bags
1 - food ration
10 - instant hot chocolate	FIRST AID:
12 - food bars	1 - basic first aid kit
1 - water treatment kit
FIRE:
1 - fire starting kit

Selection of clothing and wearable personal protective equipment is discussed in OHS Guidelines G7.37-1 and G7.37-2.

G7.36 Heated shelters

Issued January 1, 2005

Section 7.36 of the OHS Regulation states:

If a worker is exposed to a thermal environment with an equivalent chill temperature less than -7°C (19°F), as determined using the criteria for the cooling power of wind on exposed flesh in the cold stress section of the ACGIH Standard, a nearby heated shelter must be available to the worker.

The intent of a heated shelter is to allow workers the opportunity to come out of the cold and warm themselves. The outer layer of clothing should be removed, and remaining clothing should be loosened to permit sweat to evaporate. Workers should be encouraged to use the shelter at regular intervals. Signs and symptoms indicating that the shelter should be used are:

• Onset of heavy shivering
• Minor frostbite (frostnip)
• Feeling of excessive fatigue
• Drowsiness, irritability or euphoria

A heated vehicle may be used as a heated shelter. In cases where workers are in remote or isolated areas without provision of vehicles capable of being heated (such as all-terrain vehicles or snowmobiles) or in cases where workers are on foot, workers should carry adequate equipment and supplies to permit the timely assembly of a heated shelter, if necessary.

G7.37-1 Clothing (whole body)

Issued January 1, 2005

Section 7.37(1) of the OHS Regulation states:

A worker who is or may be exposed to the conditions referred to in section 7.33 must wear adequate insulating clothing and personal protective equipment.

The most widely used approach to dressing for work in cold environments is to use multiple layers of clothing. Generally, three layers of clothing are used:

• An inner layer that absorbs moisture and keeps it away from the skin.
• A second insulating layer that helps keep a layer of air trapped around the body.
• An outer layer that keeps dust, dirt, wind, and moisture away from the previous layer and that can be easily removed to prevent the buildup of body heat. In wet environments, the outer layer should be waterproof.

The insulative value of clothing selected should be based upon the equivalent chill temperature of the work environment and the anticipated metabolic rate of the work activity. Wearing too much clothing can lead to sweating, and wet clothing causes greater heat loss and increases the risk of developing hypothermia.

Many manufacturers of insulated garments provide guidance for recommended temperature and metabolic rate ranges for their clothing. There are also several standards that recommend the insulative value of clothing for use with a given temperature and metabolic rate.

An example of a standard for selecting clothing is the required insulation value or IREQ. For more information on IREQ see the following:
Holmér, Ingvar. "Cold Stress: Part I - Guidelines for the Practitioner." International Journal of Industrial Ergonomics 14:139-149 (1994).

The IREQ value, in units of clo, is selected from the following chart based upon metabolic rate and ambient temperature. Once the IREQ is determined, clothing ensembles offering the same value of insulation should be selected. Examples of basic insulation values for different clothing ensembles are listed in the following table.

For further information pertaining to IREQ or other standards that can be used to help select insulated clothing, please contact your local WCB office.

IREQ values needed to maintain low-level physiological strain

Examples of basic insulation values of clothing:

Clothing ensemble	Basic insulation value (clo)
Briefs, short-sleeved shirt, fitted trousers, calf-length socks, shoes	0.5
Briefs, undershirt, underpants, shirt, overalls, calf-length socks, shoes	1.0
Briefs, T-shirt, shirt, fitted trousers, insulated coveralls, calf-length socks, shoes	1.5
Underpants, undershirt, shirt, trousers, jacket, overjacket, overtrousers, socks, shoes, hat, gloves	2.0
Arctic clothing systems	3-4.5
Sleeping bags	3-8

G7.37-2 Clothing (extremities)

Issued January 1, 2005

Section 7.37(1) of the OHS Regulation states:

A worker who is or may be exposed to the conditions referred to in section 7.33 must wear adequate insulating clothing and personal protective equipment.

OHS Guideline G7.34-1 includes general assessment guidelines for protecting the hands. In addition, mittens rather than gloves should be worn when the air temperature is less than -17°C (0°F). Gloves and mittens should have removable liners so they can be effectively dried.

Footwear for use in cold environments should be insulated and should also have removable insoles for effective drying.

Exposed areas of the head and neck should be protected against heat loss and the danger of frostbite by use of adequate head covering and/or facemasks. This is extremely important when equivalent chill temperatures fall within the "increasing danger" portion of the "Cooling Power of Wind" ACGIH table provided in OHS Guideline G7.33-3.

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