Hello, I am Chris Jacomme, and I’m an industrial hygienist with the Department of Labor & Industries, Division of Occupational Safety and Health. In February, 2012, I investigated an incident where six workers were poisoned by carbon monoxide while operating a propane powered flooring removal machine in an office building.
In this incident, the propane-powered flooring removal machine, in the red circle, was being operated in a 22,000 square foot office space, removing ceramic tile. Although fans had been set up to move air around this office space, they did not vent to the outside and the building ventilation system had been shut off. The flooring removal machine used here was similar to the one shown in the video clip in the next slide.
The six workers, including the flooring removal machine operator, had been working in this space for about four hours and began feeling ill and having headaches. Soon thereafter, their foreman had them evacuate the office space and go outside. Because they continued to feel sick, the employer then directed all of them to go to the local hospital where they were treated for carbon monoxide poisoning.
Carbon monoxide measurements were taken at the tailpipe of the flooring removal machine shortly after the poisoning incident. The instrument showed extremely high levels of carbon monoxide being emitted – over 10% -as shown in this photo. It was also discovered that the choke cable on this rental machine was out of adjustment, causing the machine to run with the choke completely engaged. This resulted in incomplete combustion of the propane fuel and excessive amounts of carbon monoxide being generated. When the choke was disengaged, the levels of carbon monoxide at the tailpipe dropped to .01% (point zero one per cent).
Carbon monoxide levels are often measured in parts per million. The malfunctioning flooring removal machine was emitting over 100,000 parts per million into the work area over the course of about four hours. The estimated levels of carbon monoxide in the air of the office space were 165 to 265 parts per million, calculated from the amount of carbon monoxide measured in the blood of the exposed workers at the hospital. The permissible exposure limit or PEL for carbon monoxide is 35 parts per million over a period of 8 hours. Five workers recovered completely from their exposures, but one experienced long-term complications.
The employer was cited for not testing the air in the workplace for carbon monoxide while operating an internal combustion engine in an enclosed space and for exposing workers to excessive carbon monoxide levels. It is a common misconception that propane–powered equipment does not emit carbon monoxide. However, even when these machines are properly tuned and adjusted, they still emit some carbon monoxide. Rental equipment is often not properly maintained or adjusted, as was the case in this incident, resulting in the emission of high levels of carbon monoxide. Since carbon monoxide is colorless and odorless, there is no way levels can be known without regular air monitoring. Let’s keep Washington Safe and Working by always testing for carbon monoxide when operating propane powered equipment indoors.