Worker exposed to hazardous gas at mushroom composting operation

At a mushroom composting facility, run-off liquids and solids were collected in an open tank until needed for soaking bales of straw. The materials remained in the tank for a few days during warm weather. As a worker was removing straw floating on the surface, he was exposed to a hazardous gas, likely hydrogen sulphide. The worker had trouble breathing, eye irritation, and a sore throat.

Mushroom compost typically includes water, chicken manure, straw, and gypsum. The run-off liquids and solids are often collected so that they can be re-used. These materials can stagnate in ponds, tanks, vessels, bunkers, or pipes. If the run-off materials are not aerated, hazardous gases (such as hydrogen sulphide, ammonia, and carbon dioxide) can be produced. Workers might be exposed to these hazardous gases or to a low-oxygen atmosphere when they open the equipment or disturb and handle the composting material. The hazardous gases can be immediately harmful and even life-threatening.

Safe work practices:

• Conduct a workplace assessment of the risk of hazardous gas exposure in the mushroom composting operation. Develop and follow a plan to control workers' exposure to hazardous gases and areas of low oxygen. Train workers and contractors to follow safe work procedures.

• Do not allow mushroom compost and run-off materials to stagnate, even for a short time, in closed or covered containers or in any areas used by workers. Stagnant materials develop low-oxygen conditions that help produce hazardous gases. This process happens more quickly in warm weather.
• Provide enough aeration of mushroom compost and run-off materials to avoid the low-oxygen conditions where hazardous gases are produced.
• Maintain equipment to prevent the buildup of sludge or other materials that can cause blockages.
• Ensure adequate ventilation in areas where hazardous gases may be produced. If the area is indoors, assess the need for mechanical ventilation.

NOTE: Vietnamese and Punjabi translations of this hazard alert are available here.