Preventing Carbon Monoxide Exposure at Work

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Woman and man workers running out of the construction site, suffocating. Carbon monoxide poisonous gas cloud.

Carbon monoxide (CO) is a colorless, odorless, tasteless gas that is lighter than air. Carbon monoxide is present in the air in low concentrations, but it can also be created when organic materials catch fire, but don’t completely burn. High concentrations of carbon monoxide can interfere with the oxygen-carrying capacity of the bloodstream, and prolonged exposure can cause serious injury and death. The Centers for Disease Control and Prevention (CDC) reports that carbon monoxide poisoning kills more than 400 people and hospitalizes 4,000 every year. People who work with or around heavy machinery, fire or ignition sources should recognize the risks of carbon monoxide exposure and how to protect themselves.

What is Carbon Monoxide?

CO molecule

Carbon monoxide is a chemical compound made of one carbon atom and one oxygen atom. Most carbon monoxide is created when carbon-based materials are burned. Ideally, a fire’s chemical reaction bonds carbon and oxygen atoms to form carbon dioxide, which is one carbon atom and two oxygen atoms. But when there isn’t enough oxygen present to fully burn the fuel, such as operating a stove or engine in an enclosed space, carbon monoxide is created instead. Fuels such as coal, natural gas, wood, oil, and gasoline can all create carbon monoxide when burned. Many pieces of equipment we use every day can emit carbon monoxide, including:

  • Vehicles (cars, trucks, boats, planes)
  • Cooking Equipment (stoves, ovens, grills)
  • Heating equipment (fireplaces and furnaces
  • Gas-powered portable generators

How Does Carbon Monoxide Affect the Human Body?

Carbon monoxide is a highly toxic gas that can affect the human body in a variety of negative ways. When humans and animals breathe in carbon monoxide, it can bond with hemoglobin, an iron-protein component in red blood cells responsible for carrying oxygen throughout the body. Carbon monoxide bonds with hemoglobin 300 times more easily than oxygen, and even a small amount of carbon monoxide can drastically reduce the amount of oxygen sent to the heart, brain and other vital organs.


Determining whether someone has carbon monoxide poisoning can be difficult. Victims’ specific symptoms can vary depending on their overall health and fitness levels, but it can often resemble flu symptoms. Brief exposure to low levels of carbon monoxide can cause a mild headache and make it more difficult to breathe while being active. Continued exposure can lead to more severe symptoms such as dizziness, confusion, weakness, upset stomach, and vomiting. Victims exposed to high concentrations of carbon monoxide can lose consciousness or even die if they aren’t moved to fresh air right away. Even low levels of carbon monoxide can have long-term negative effects on those who are consistently exposed. Long-term exposure to carbon monoxide can cause learning and memory impairments, emotional and personality changes, and sensory and motor skill disorders.

Who is at High Risk of Carbon Monoxide Exposure?

Carbon monoxide prevalent facility

Carbon monoxide can be found in many workplaces, but some work environments expose workers to more carbon monoxide than others. Harmful levels of carbon monoxide may be found in boiler rooms, oil refineries, paper mills, steel mills, breweries, and enclosed garages, among many others. Work performed in confined spaces may also expose workers to carbon monoxide. Workers in certain occupations often have an elevated risk of carbon monoxide exposure, including welders, drivers, auto mechanics, firefighters, and dockworkers. Certain groups of people are especially susceptible to carbon monoxide poisoning, such as smokers, people with lung or heart conditions and people living or working at high altitudes.

Workplace Controls for Carbon Monoxide

hierarchy of hazard control list

When employers identify a health or safety risk to their employees, they often use the hierarchy of hazard controls to protect against that hazard. The first step involves eliminating the hazard entirely or substituting it for something less hazardous. For example, removing a gas-powered engine from the work area eliminates a source of carbon monoxide. Using gas designed for lanterns – which creates less carbon monoxide than gasoline – instead of using gasoline is a form of substitution. If carbon monoxide sources can’t be eliminated or substituted out of the work area, engineering controls should be used. Engineering controls change the work process or environment to either reduce the level of hazard, or physically prevent workers from coming into contact with a hazard. Ventilation systems are a common and effective engineering control used when workers are around carbon monoxide in a closed room or confined space.

If a hazard can’t be removed from the work area or engineered away from workers, administrative controls are the next most-effective control. Administrative controls are workplace policies, safe work practices, and training that helps protect workers from hazards or reduce their exposure to hazards. For example, many employers have policies that prohibit using gas-powered equipment and tools in confined spaces or other poorly-ventilated areas. Employers should regularly test for carbon monoxide or other air contaminants and should also implement consistent air monitoring with audible alarms in work areas where carbon monoxide is often present. Finally, if carbon monoxide levels in a work area exceed OSHA’s exposure limits, workers should be removed until carbon monoxide levels can be lowered below the exposure limits.

If engineering and administrative controls don’t completely remove a hazard from a work area, PPE is used to protect workers. Respirators are the most common type of PPE used to protect workers from airborne contaminants such as carbon monoxide. If employees require respiratory protection, the employer must develop a respiratory protection program, and must comply with OSHA’s respiratory protection standard. This includes providing respirators, training and medical evaluations at no cost to affected employees. Employers are also responsible for ensuring that employees are properly trained and that employees wear their respirators whenever necessary. When carbon monoxide exposure is a risk, employers should provide a NIOSH-certified full-facepiece respirator with a supply of breathable air.


Because we can’t see or smell carbon monoxide, it can be a particularly dangerous substance. Knowing what work areas or equipment could expose workers to carbon monoxide will help workers protect themselves from exposure and help employers implement necessary controls to create a safe work environment.

OSHA Carbon Monoxide Quick Card

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