Carbon Monoxide Poisoning

Carbon monoxide (CO) is a poisonous, colorless, odorless and tasteless gas. 

Although it has no detectable odor, CO is often mixed with other gases that do 

have an odor. So, you can inhale carbon monoxide right along with gases that you 

can smell and not even know that CO is present. 

CO is a common industrial hazard resulting from the incomplete burning of material 

containing carbon such as natural gas, gasoline, kerosene, oil, propane, coal, or 

wood. Forges, blast furnaces and coke ovens produce CO, but one of the most 

common sources of exposure in the workplace is the internal combustion engine.

How does CO harm you?

Carbon monoxide is harmful when breathed 

because it displaces oxygen in the blood and 

deprives the heart, brain and other vital organs 

of oxygen. Large amounts of CO can overcome 

you in minutes without warning — causing you 

to lose consciousness and suffocate. 

Besides tightness across the chest, initial 

symptoms of CO poisoning may include 

headache, fatigue, dizziness, drowsiness, 

or nausea. Sudden chest pain may occur in 

people with angina. During prolonged or 

high exposures, symptoms may worsen and 

include vomiting, confusion and collapse in 

addition to loss of consciousness and muscle 

weakness. Symptoms can vary widely from 

person to person. CO poisoning may occur 

sooner in those most susceptible: young 

children, the elderly, people with lung or heart 

disease, people at high altitudes, or those who 

already have elevated CO blood levels, such as 

smokers. Also, CO poisoning poses a special 

risk to fetuses. 

CO poisoning can be reversed if caught in time. 

But even if you recover, acute poisoning may 

result in permanent damage to the parts of your 

body that require a lot of oxygen such as the 

heart and brain. Significant reproductive risk is 

also linked to CO.

Who is at risk?

You may be exposed to harmful levels of CO in 

boiler rooms, warehouses, petroleum refineries, 

pulp and paper production, and steel production; 

around docks, blast furnaces, or coke ovens; or 

in one of the following occupations:

• Welder

• Garage mechanic

• Firefighter

• Carbon-black maker

• Organic chemical synthesizer

• Metal oxide reducer

• Longshore worker

• Diesel engine operator

• Forklift operator

• Marine terminal worker

• Toll booth or tunnel attendant

• Customs inspector

• Police officer

• Taxi driver

What can you do if you suspect that 

someone has been poisoned with CO?

When you suspect CO poisoning, promptly taking 

the following actions can save lives:

• Move the victim immediately to fresh air in an 

open area.

• Call 911 or another local emergency number 

for medical attention or assistance.

• Administer 100 percent oxygen using a tightfitting mask if the victim is breathing.

FactSheet
• Administer cardiopulmonary resuscitation if 

the victim has stopped breathing.

Warning: You may be exposed to fatal levels 

of CO poisoning in a rescue attempt. Rescuers 

should be skilled at performing recovery 

operations and using recovery equipment. 

Employers should make sure that rescuers 

are not exposed to dangerous CO levels when 

performing rescue operations.

How can employers help prevent 

CO poisoning?

To reduce the chances of CO poisoning in the 

workplace, employers should take the following 

actions:

• Install an effective ventilation system that will 

remove CO from work areas.

• Maintain equipment and appliances (e.g., 

water heaters, space heaters, cooking ranges) 

that can produce CO in good working order 

to promote their safe operation and to reduce 

CO formation.

• Consider switching from gasoline-powered 

equipment to equipment powered by 

electricity, batteries, or compressed air if it 

can be used safely.

• Prohibit the use of gasoline-powered engines 

or tools in poorly ventilated areas.

• Provide personal CO monitors with audible 

alarms if potential exposure to CO exists.

• Test air regularly in areas where CO may be 

present, including confined spaces. See Title 

29 of the Code of Federal Regulations (CFR) 

1910.146.

• Use a full-facepiece pressure-demand selfcontained breathing apparatus (SCBA) 

certified by the National Institute for 

Occupational Safety and Health (NIOSH), or a 

combination full-facepiece pressure demand 

supplied-air respirator with auxiliary selfcontained air supply in areas with high CO 

concentrations, i.e., those with immediately 

dangerous to life and health atmospheres. 

(See 29 CFR 1910.134.)

• Use respirators with appropriate canisters, 

in conjunction with personal CO monitoring, 

for short periods under certain circumstances 

where CO levels are not exceedingly high.

• Educate workers about the sources and 

conditions that may result in CO poisoning 

as well as the symptoms and control of CO 

exposure.

In addition, if your employees are working in 

confined spaces where the presence of CO is 

suspected, you must ensure that workers test for 

oxygen sufficiency before entering.

What can employees do to help prevent 

CO poisoning?

Employees should do the following to reduce the 

chances of CO poisoning in the workplace:

• Report any situation to your employer that 

might cause CO to accumulate.

• Be alert to ventilation problems — especially 

in enclosed areas where gases of burning 

fuels may be released.

• Report promptly complaints of dizziness, 

drowsiness, or nausea.

• Avoid overexertion if you suspect CO 

poisoning and leave the contaminated area.

• Tell your doctor that you may have been 

exposed to CO if you get sick.

• Avoid the use of gas-powered engines, 

such as those in powered washers as well 

as heaters and forklifts, while working in 

enclosed spaces.

What are the OSHA standards for 

CO exposure?

• The OSHA PEL for CO is 50 parts per million 

(ppm). OSHA standards prohibit worker 

exposure to more than 50 parts of CO gas per 

million parts of air averaged during an 8-hour 

time period.

• The 8-hour PEL for CO in maritime operations 

is also 50 ppm. Maritime workers, however, 

must be removed from exposure if the CO 

concentration in the atmosphere exceeds 

100 ppm. The peak CO level for employees 

engaged in Ro-Ro operations (roll-on rolloff operations during cargo loading and 

unloading) is 200 ppm.

Workers’ Rights

Workers have the right to:

• Working conditions that do not pose a risk of 

serious harm.

• Receive information and training (in a 

language and vocabulary the worker 

understands) about workplace hazards, 

methods to prevent them, and the OSHA 

standards that apply to their workplace.

• Review records of work-related injuries 

and illnesses.
DSG FS-3522 04/2012

This is one in a series of informational fact sheets highlighting OSHA programs, policies or 

standards. It does not impose any new compliance requirements. For a comprehensive list of 

compliance requirements of OSHA standards or regulations, refer to Title 29 of the Code of Federal 

Regulations. This information will be made available to sensory-impaired individuals upon request. 

The voice phone is (202) 693-1999; teletypewriter (TTY) number: (877) 889-5627.

• File a complaint asking OSHA to inspect

their workplace if they believe there is a

serious hazard or that their employer is not

following OSHA’s rules. OSHA will keep all

identities confidential.

• Exercise their rights under the law without

retaliation, including reporting an injury or

raising health and safety concerns with their

employer or OSHA. If a worker has been

retaliated against for using their rights, they

must file a complaint with OSHA as soon as

possible, but no later than 30 days.

For additional information, see OSHA’s Workers 

page (www.osha.gov/workers).

How to Contact OSHA

Under the Occupational Safety and Health Act 

of 1970, employers are responsible for providing 

safe and healthful workplaces for their employees. 

OSHA’s role is to help ensure these conditions 

for America’s working men and women by 

setting and enforcing standards, and providing 

training, education and assistance. For more 

information, visit www.osha.gov or call OSHA at 

1-800-321-OSHA (6742), TTY 1-877-889-5627.