Carbon Monoxide

Carbon monoxide, chemical formula CO, is a highly toxic gas at room temperature that is odorless and colorless. Carbon monoxide most often occurs as a by-product formed by the incomplete combustion of carbon-containing materials, such as wood and petrochemicals (e.g., gasoline and liquefied propane gas).

Carbon Monoxide

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What are some common uses of carbon monoxide?

Industrially, carbon monoxide is used in the manufacture of many organic and inorganic chemicals. Carbon monoxide is used in the production of hydrogen gas by reacting it with water vapor at high temperatures to yield carbon dioxide and hydrogen gas, the latter of which is used, for example, to react with nitrogen to produce ammonia. Reaction of carbon monoxide with caustic alkalies yields alkali formates, which are then converted into formic acid, or alkali oxalates, which are used to produce oxalic acid.

Reaction of carbon monoxide with certain metals yields compounds called carbonyls. The reaction of nickel with carbon monoxide to give nickel carbonyl is used as a means of purifying nickel metal.

What are the hazards associated with carbon monoxide?

Health hazards associated with carbon monoxide are the result of two principal factors. First, carbon monoxide is miscible with air and acts as a simple asphyxiant by displacing oxygen. Second, carbon monoxide irreversibly binds with hemoglobin to form carboxyhemoglobin, thus reducing the number of red blood cells available to transport oxygen to other cells of the body.

Symptoms of acute overexposure to carbon monoxide include headache, nausea, vertigo, headache, unconsciousness and, in the worst case, death. Individuals with pre-existing heart disease can experience chest pain. Symptoms of chronic overexposure to carbon monoxide include, but are not limited to, headache, anorexia, exhaustion and dizziness.


What can I do to protect myself and others?

Engineering and Work Practice Controls. Equipment powered by internal combustion engines (e.g., propane-powered concrete cutting saws, portable generators) should never be used in enclosed spaces where employees are working or in areas where the engine exhaust can become entrained in a facility’s ventilation. Forklifts fueled by liquefied propane gas (LPG) should be properly serviced and maintained to ensure maximum combustion efficiency and reduced carbon monoxide emissions. Adequate ventilation, which includes fresh air, should be maintained when operating forklifts indoors (e.g., warehouses).

Personal Protective Equipment. When substitution is not feasible and engineering controls are not adequate to maintain airborne exposures below the carbon monoxide permissible exposure limit (PEL), air-supplied respiratory protection must be used in conjunction with an effective respiratory protection program. Because carbon monoxide can also act as a simple asphyxiant, air-purifying respirators afford no protection against carbon monoxide accumulation.

What resources are available to assist employers?

Training and Outreach Services

Presentations on a variety of topics associated with carbon monoxide exposure are available to assist employers in training their staff. These include:  hazard communication; respiratory protection; and personal protective equipment. Each of these presentations should be modified to address site-specific conditions and hazards. 

In addition, the education, training and technical assistance bureau provides free online safety and health training and outreach services (i.e., speaker's bureau requests, safety booths) upon request. 

Lastly, the NCDOL Library offers free safety and health videos (including streaming video services) and related research assistance on consensus standards (i.e., ANSI, NFPA, NEC). 

Safety and Health Programs

Example safety and health programs are available for employers to download and adapt to their specific conditions. Safety and health programs relative to carbon monoxide include: hazard communication program; personal protective equipment program; and respiratory protection program.

A-Z Safety and Health Topics

More information related to carbon monoxide can be found on the A-Z topics pages for hazard communication, personal protective equipment (PPE), and respiratory protection.

Consultation Services

The consultative services bureau provides free and confidential onsite consultation regarding worksite safety and health hazards.


Which standards apply?

OSH has adopted the following standards which are applicable to carbon monoxide in North Carolina. Note: Please also check the standards information and activity webpage to see if there has been any recent or upcoming regulatory activity on this topic. 

General Industry

Maritime, Marine Terminals


Other Applicable Standards

The Which OSHA Standards Apply webpage can also help identify other standards that may be applicable to this topic.


Where can I learn more?

Industry Guides

Technical Assistance

If you would like to receive interpretive guidance on this or any other OSH standard or topic, you can submit your questions using the Ask OSH web form, by e-mail to or by calling 919-707-7876.