*Avoiding Carbon Monoxide Exposure*
By: Fuchi
22 December 2005


Carbon monoxide (CO) is an invisible, odorless poison. It's so hard to detect without monitors that it kills hundreds of people in their homes and on the job every year.

Organic materials such as wood, oil, or gasoline produce CO when they burn in an area with a limited supply of air or oxygen. CO is also generated when a flame contacts a surface that's cooler than the flame gas's ignition temperature. Many industries also use carbon monoxide liquid, which comes in cylinders. But the most common source of carbon monoxide is incomplete fuel burning-often from a motor vehicle or a furnace-in an airtight building. CO is most dangerous in winter, when closed doors and windows eliminate natural ventilation. People don't realize CO is present, since you can't see or smell it. But you can die in minutes if you inhale large amounts of carbon monoxide. Inhaling even small amounts can cause health problems. So it's important to be alert to the risks of this deadly gas.

General Hazards

Carbon monoxide is so dangerous because it gets into the blood when it's inhaled. Once it's there, CO interferes with the blood's ability to send oxygen to the tissues-including the heart and the brain. In the worst cases, that can cause permanent brain damage or even death. It's a double risk for pregnant women, because their blood can carry the CO to the baby.

Business and home heating systems that burn oil, gas, or coal produce CO. So do foundries, blast furnaces, mining, gas works, refuse plants, and such processes as chemical synthesis, carbide and formaldehyde manufacturing, and acetylene welding in enclosed areas.

The most common source of CO, however, is exhaust from a car, truck, or forklift. That creates risks for mechanics and drivers as well as people who work on or around loading docks, forklift repair areas, etc. If you work with liquid CO, you also have to be aware of its other hazards. The liquid is flammable and can cause frostbite-type burns if it comes in contact with your skin.

OSHA Regulations

OSHA lists carbon monoxide in its table of air contaminants (29 CFR 1910.1000(a) Table Z-1). The permissible exposure limit (PEL) is 50 parts per million (ppm) of air, or 55 milligrams per cubic meter of air, averaged over an eight-hour workshift. The American Industrial Hygiene Association (ACGIH) believes short-term exposure for 15-minute periods shouldn't top 400 ppm or 440 milligrams per cubic meter. And the National Institute of Occupational Safety and Health says a level of 1,500 ppm is immediately dangerous to life and health.

Identifying Hazards

Although carbon monoxide is invisible and odorless, there are various sensors that can detect and measure its presence in the air and alert you when levels are dangerous. There are also home versions of carbon monoxide detectors that serve the same purpose.

If you're working in an area that has no detector, it's hard to identify CO hazards. So you have to pay special attention to any symptoms that could be caused by CO poisoning. Unfortunately, these symptoms are much like those for flu or other ailments. So don't take chances if you're in an enclosed area that could contain CO. If you're at work, report the symptoms so that we can check the CO levels. If they're too high, we'll have to evacuate the area and take action to reduce the carbon monoxide.

If you're at home, alert others in the house who may not know how to recognize signs of CO exposure. Then get to fresh air immediately!

CO Exposure Symptoms

Symptoms that could indicate you're in the early stages of CO exposure include:

CO poisoning victims have pale skin when they first inhale the substance. As exposure continues, the skin turns

red. People with heart disease may also experience chest pains. CO exposure can, in fact, aggravate heart disease,

as well as anemia and respiratory illnesses.

CO exposure symptoms may develop faster and get worse in certain situations. The situations that can increase CO inhalation dangers include:

and more severely than nonsmokers.

Protection Against Hazards

The first step in protecting yourself and others from CO exposure is to identify the equipment that could pose risks. When possible, enclose CO sources so the gases can't be inhaled. To help ensure that fuels burn properly, heating systems and other fuel-burning equipment need regular, thorough maintenance. That's important at home as well as at work. Heating equipment leaks are a common source of CO poisoning.

Vehicles, the biggest source of CO, need careful maintenance, too. Be sure they're well-tuned and burn fuel properly. Also look out for exhaust and pipe leaks and for body rot. Drivers have been overcome when exhaust leaked into the cab of a car or truck. If in doubt about your vehicle's condition, keep a window slightly open at all times.

Take special care with vehicles used indoors, including forklifts.

Vent gases out through an exhaust pipe when motor vehicles must run in enclosed spaces.

Turn vehicles off during loading or unloading or any time they're not moving. They generate plenty of CO when they're idling.

Don't warm up a car or truck in a closed garage or other enclosed space. It only takes minutes to be overcome by the CO in the exhaust. In addition, the carbon monoxide can spread into the adjoining work area or home and sicken unsuspecting people.

Be especially alert to CO dangers if you drive a forklift into a truck body or even a dead-end aisle. Fumes can quickly build up to dangerous levels.

Good ventilation is the best way to prevent CO buildup in these danger areas and other enclosed spaces. When doors and windows are closed or too far away to help, use general and local exhaust ventilation to keep CO at safe levels. Ventilation is especially crucial in small areas, where CO can reach high concentrations quickly. Ventilation systems also need regular inspections and maintenance. Before you run any CO-generating equipment, make sure ventilation motors and fans are running. Check hose and duct connections to make sure no holes or blockages could prevent proper ventilation system operation.

Sometimes ventilation can't provide enough protection. If detectors measure unsafe CO levels, or if you can't judge the amount of CO in the air, you'll need a supplied air respirator. You'll also need PPE that prevents skin and eye contact for work with liquid CO. Equip yourself with impervious clothing and gloves, a face shield, and splash-proof safety goggles.

Safety Procedures

One of the best protections against CO poisoning is to react quickly to any signs of exposure. That's critical, since you can't see or smell CO and it can hit quickly and severely. If you or a co-worker experiences any symptoms that could result from CO exposure, report the problem immediately so we can protect others. Then move to fresh air. A few minutes in fresh air will usually relieve the milder symptoms of CO exposure. Administering pure oxygen can help the body get rid of the CO more quickly. A CO inhalation victim who isn't breathing must have artificial respiration and immediate medical attention. Even without such dramatic symptoms, it's wise to get medical attention if you've inhaled carbon monoxide.

If you have suffered the effects of CO inhalation, your body will probably need a day or two of bed rest to recover. If you work with liquid CO, avoid exposure by treating it like any hazardous chemical. Check the label and MSDS for hazard and protective information. Store cylinders properly in areas equipped with CO detector alarms. It's also important to check CO cylinders regularly for leaks. If you do detect a leak, report it immediately. Then evacuate while trained personnel, equipped with protective clothing and respirators, handle the problem. They'll ventilate the area to disperse the gas and shut off any ignition sources to prevent a fire. Then they'll either stop the leak or take the leaking cylinder outside for repair.

If you have skin contact with liquid CO, remove any contaminated clothing immediately and thoroughly rinse the skin.


Carbon monoxide has been called the silent killer. But most overexposure can be avoided. Keep all vehicles, heating systems, and other combustion-producing equipment in top condition. Operate this equipment only in well-ventilated areas. And don't ignore or brush off symptoms of CO exposure. It could be the flu, but it could be carbon monoxide poisoning. Get to fresh air immediately. Then find out if CO caused the problem and take action to ventilate the area and fix the equipment so it doesn't put you or anyone else at risk.

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