OSH Basics - CO: The Silent Killer at Work

January 15, 2003

CO: The Silent Killer at Work

By Sean M. Alvarez, CSP

Referred to in many households as "the silent killer", Carbon Monoxide (CO) is not just a residential hazard. Your workplace could be at risk as well. This month's OSH Basics familiarizes you with a common workplace poisoning hazard which can easily be mitigated.

WHAT IS CO?

CO is a common industrial hazard resulting from the incomplete burning of natural gas and any other material containing carbon such as gasoline, kerosene, oil, propane, coal or wood.

During normal combustion, each atom of carbon in the burning fuel joins with two atoms of oxygen - forming a relatively harmless gas called carbon dioxide. When there is insufficient oxygen to ensure complete combustion of the fuel, each atom of carbon links up with only one atom of oxygen - forming a colorless, odorless, tasteless and poisonous gas called carbon monoxide.

While having no detectable odor, CO readily mixes with other gases that do have an odor. So, you can easily inhale carbon monoxide right along with gases that you can smell and not even know that CO is present.

Although present in liquid form under high pressure, carbon monoxide (CO) is most commonly encountered as a gas. This gas is the leading cause of accidental poisoning deaths in America, resulting in more than 1700 suicides and over 500 unintentional deaths every year in the United States, according to the Journal of the American Medical Association (JAMA). An additional 10,000 seek medical attention.

HOW DOES CO HARM WORKERS?

Carbon monoxide is an asphyxiant that exerts its toxic effects by combining with the hemoglobin of the blood. This combination decreases the amount of oxygen that can successfully combine with the hemoglobin and be delivered to the tissues.

Simply put, carbon monoxide takes the place of the oxygen, causing your tissues and organs to suffocate and eventually stop working.

Just about any process or piece of equipment using a flame can become a producer of CO. Forges, blast furnaces and coke ovens all produce CO.

Even basic welding procedures generate the gas. According to the Occupational Safety and Health Administration (OSHA), welding and cutting may produce significant amounts of carbon monoxide. In addition, welding operations that use carbon dioxide as the inert gas shield may produce hazardous concentrations of carbon monoxide in poorly ventilated areas.

Of all CO producers, one of the most commonly overlooked in the workplace is the internal combustion engine. In fact, many injuries and deaths occur from small engines and tools.

Many people using gasoline-powered tools such as high-pressure washers, concrete cutting saws, power trowels, floor buffers, welders, pumps, compressors, and generators in buildings or semi-enclosed spaces have been poisoned by carbon monoxide.

The National Institute for Occupational Safety and Health (NIOSH) provides these examples of such poisonings.

According to 29 CFR, Table Z-1, the current OSHA permissible exposure limit (PEL) for carbon monoxide is 50 parts per million (ppm) parts of air as an 8-hour time-weighted average (TWA) concentration.

The Consumer Product Safety Commission reports that health effects from exposure to CO levels of approximately 1 to 70 ppm are uncertain, but most people will not experience any symptoms. Some heart patients might experience an increase in chest pain.

As CO levels increase and remain above 70 ppm, symptoms may become more noticeable (headache, fatigue, nausea, dizziness). Since symptoms of mild exposure to carbon monoxide are similar to the flu, many victims of CO poisoning are misdiagnosed.

As CO levels increase above 150 to 200 ppm, disorientation, muscle weakness, unconsciousness, and death are possible.

Additionally, pregnant women, unborn babies, newborns, people with heart or respiratory problems, and the elderly may be more vulnerable to CO poisoning.

Developing and implementing a Carbon Monoxide Control Program at your workplace should help to minimize CO exposures:

Each year, several thousands of people at home and at work are poisoned by carbon monoxide. Do not be fooled into thinking that the silent killer is only a residential hazard -- This killer goes to work as well!

Carbon Monoxide and You - Montana State University Extension. Publication date: February 1983