Carbon Monoxide Poisonings at Indoor Work Places

In recent months a total of 11 employees were poisoned by carbon monoxide (CO) at 3 separate work places.

DOSH inspections tied the poisonings to propane- or liquid gas-powered equipment used in poorly ventilated, enclosed spaces. Built-in ventilation systems (HVACs) in these work spaces were either taken out of service (to avoid dust contamination during work activities) or not capable of removing a buildup of CO gas.  Hazard prevention starts with recognition that CO can become a danger on job sites like the ones described here. Dangerously high levels of CO built up in the air:

• After just 2 hours of pressure washing a concrete floor inside a 200 foot-long townhouse garage  
• Within 1 ½ hours of operating a power screed and two riding-power trowels inside a 12,000 sq.ft. warehouse. 
• During the work shift while using a floor-scraper machine to remove tile inside a 22,000  sq.ft. office space. 

Industrial fans and negative-pressure air machines are often not enough to stop a serious CO build up, even in large spaces. Testing the air for CO during work activities will tell you if your ventilation setup is keeping CO below regulatory limits. If high CO levels persist, you may need to add a portable ventilation system that can ensure enough contaminated air is effectively vented to the outside and replaced by fresh air.

To find help or learn more about CO hazards, rules, and regulatory limits, visit L&I’s  Carbon Monoxide topic page. This page also provides hazard prevention, training, and other resources to help you keep your employees safe and working.

Please share this bulletin with others in your industry and safety networks.

If you have questions or comments, please contact Nichole.Rose@lni.wa.gov.