Carbon Monoxide: An Undetectable Killer
Rod Stanley, Director of Construction Operations for MEMIC Loss Control, called recently to alert me of the first carbon monoxide claim of the winter.
Three workers were loading trucks inside a warehouse in early December. Outside temperatures were well below 20 degrees Fahrenheit, and coupled with a heated shop, it seemed like a good reason to keep the loading doors closed. Starting work at 6 a.m., two forklifts were being used to transfer materials and load the trailers. Because the forklifts are fueled by propane, the workers thought the carbon monoxide hazard associated with gas or diesel-powered equipment was eliminated. They were wrong.
Around noon, one of the workers collapsed from overexposure and, luckily, one of the other two was able to call for an ambulance. The fire department responded, along with the rescue crew, and found that CO levels in the warehouse were dangerously high. Although the workers recovered, all three were transported to a local hospital for treatment.
Incidents similar to this continue to happen not only in the workplace, but in a lot of homes as well. Carbon monoxide is a byproduct of all fuel combustion – whether from generators, wood stoves, fork lifts, compressors and even charcoal. These are just some of the sources of carbon monoxide which make thousands ill and kill hundreds every year.
A common misconception is that propane-powered machines are CO-safe. A study published by the Education Safety Association of Ontario finds that propane-powered engines can produce up to 2 percent, or 20,000 parts per million (ppm), of carbon monoxide in their exhaust. OSHA has established a maximum level of 50 ppm for workers as an 8-hour time-weighted average, and the American Conference of Governmental Industrial Hygienists recommends that level not to exceed 35 ppm.
One of the disturbing points about such an exposure as carbon monoxide is the ease in which it can be prevented. The means of prevention begins with the literature that comes with the product and quite often is also stenciled somewhere on the product itself. A common warning for many heating devices reads “Use only in a well-ventilated area.” Even a bag of charcoal will tell the user how to protect themselves!
Unfortunately these warnings often go unheeded. In any case, whether it's at work or at home, keeping employees and/or family members from becoming sick, or worse, comes down to the user. Basic protective measures include carbon monoxide area and personal monitors that automatically detect harmful levels and set off alarms that can warn building occupants and/or workers.
An excerpt from a NIOSH study illustrates how rapidly carbon monoxide can build up, even in a seemingly well-ventilated work space:
“A 5.5-horsepower, gasoline-powered pressure washer was operated inside an 8,360-cubic-foot, double-car garage using two ventilation scenarios. In the first or "worst-case" scenario, all doors, windows, and vents were closed. Breathing-zone concentrations of CO reached 200 ppm within 5 minutes, 1,200 ppm (IDLH value) within 15 minutes, and 1,500 ppm within 19 minutes; they continued to increase thereafter. In the second or "best-case" scenario, the two double-car garage doors and one window were left open and the vent was unsealed; breathing-zone concentrations of CO reached 200 ppm within 3 minutes and peaked at 658 ppm within 12 minutes. The results from the simulations indicate that acutely toxic concentrations of CO greater than 200 ppm (NIOSH ceiling) can be quickly generated within 3 to 5 minutes near a pressure washer operated indoors (even when passive ventilation is provided), and IDLH concentrations of 1,200 ppm can be generated rapidly in enclosed spaces.”
There are numerous websites that provide detailed information about carbon monoxide hazards and methods of protection. Several of these are listed below, but as a reminder, please make sure to always follow manufacturer recommendations.
As always, if you have any pointers, resources, or stories you'd like to share, I'd love to hear from you.
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