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Carbon Monoxide Poisoning in Construction, a Silent Killer

Carbon monoxide (CO) is a colorless, odorless, tasteless, highly toxic gas. It’s a byproduct of combustion and is produced whenever fuel is burned from kerosene, charcoal, diesel fuel, wood, gasoline, natural or liquefied petroleum (LP) gas, coal, propane, oil, methane and even tobacco smoke.

In a typical year, nearly 400 Americans die from CO poisoning, usually in their own home or car. Most deaths are caused by indoor use of portable gas-powered generators. CO poisoning is also a serious threat on construction jobsites year-round that tends to increase during the winter months when fuel-burning equipment and tools are used in buildings or spaces without sufficient ventilation. 

CO is virtually undetectable and, depending on the concentration, workers can become unconscious and suffocate in minutes. When inhaled, CO particles in the air rapidly enter all parts of the body, including the blood, brain, heart and muscles. CO leaves the body when you exhale, but there is a delay in eliminating the poison completely. Symptoms of exposure include:

Mild Poisoning Moderate Poisoning Severe Poisoning
  • Headache 
  • Nausea and vomiting
  • Dizziness and blurred vision
  • Asphyxia
  • Chest pain
  • Dry cough
  • Visual and auditory hallucinations
  • High blood pressure
  • Confusion
  • Syncope (fainting)
  • Chest pain
  • Loss of consciousness
  • Rhabdomyolysis
  • Loss of consciousness after two to three breaths
  • Cardiac arrest
  • Convulsions and respiratory arrest
  • Seizures
  • Coma


All workers with the potential to be exposed to carbon monoxide or CO-producing machines should be trained on its symptoms, sources and poisoning prevention. Workers trained to administer first-aid or CPR (or third parties on site in case of emergency), should also be trained on CO and present when the potential for exposure exists.

Staying Safe on the Jobsite

Construction workers use a range of tools and equipment that generate CO. Pay special attention to portable generators, space heaters, gas-powered equipment (such as wet saws) and water pumps. Take the following precautions when these potential CO hazards are present:

  • Never use this equipment in enclosed spaces, such as basements or areas where there is little to no ventilation. 
  • Windows and doors should always be left open when this equipment is in use.
  • Leave 3-4 feet of space between the generator and any ceilings or walls.
  • If using a generator outdoors, make sure it’s not placed in a location where CO could enter confined and occupied spaces, such as nearby narrow openings.

Worksite supervisors should ensure effective ventilation exists when workers are in enclosed areas. Industrial-sized fans should be placed in areas where outdoor openings and natural ventilation aren’t readily available. When possible, gas-powered equipment should be swapped out for battery or electric-powered equipment. Gas-powered saws can be replaced by hydraulic or pneumatic concrete saws.

When a hazard assessment raises concern of overexposure to CO, workers must be equipped with appropriate safety gear. Supplied air or self-contained breathing apparatuses provide workers with clean air via a fixed oxygen supply. Workers should also be equipped with CO or multi-gas monitors. Portable monitors can clip onto work belts and larger monitors can be placed next to the task.

Staying Safe at Home

To protect you and your family at home, stop the threat of CO poisoning at its source. 

Your Garage

  • Back your car out to let it warm up. Never leave it running in the confined space of a garage, particularly if the garage is attached to the home.
  • Never run lawnmowers, snowblowers or other gas-powered engines in confined areas like garages or sheds.
  • Never use ovens or grills to heat your home or garage.

Your Car

  • Never dismiss a fender bender as something you’ll get checked later. Even minor collisions can cause breaks in your car’s exhaust system, allowing CO to enter the passenger area.
  • If you get stuck in deep snow along the road and are running your car’s engine to keep warm, clear snow away from the exhaust pipe. A blocked exhaust pipe can cause CO to back up into your passenger area.

Your Home

  • Never use a cooking device – an oven, grill or camp stove – to heat your home.
  • Install a CO alarm on each level of your home. CO detectors last about five to seven years depending on the manufacturer. If an alarm sounds, do not ignore it, and exit the home to fresh air. 
  • Replace old or faulty central heating and air conditioning units. Hire a trained professional to ensure proper ventilation during installation.
  • Maintain your heating and air conditioning system regularly (usually just before each big change of season).

CO Emergency Response

If you’re involved in an CO poisoning incident at work or at home, follow these steps:

  • Call 911. 
  • Provide fresh air to the environment.
  • Check the area for elevated CO levels before entering and remove the affected person to fresh air. 
  • Remain with the person and encourage them to breathe normally while reassuring them help is on the way. 
  • Keep an eye on their condition and be prepared to administer appropriate first aid or CPR as required.

Remember, CO gas cannot be seen, smelled or heard, but it can be stopped. Mitigating CO poisoning hazards can range from using battery-powered tools and equipment and implementing adequate ventilation to using CO detectors. 

For more information about CO or help keeping your site safe, contact the LHSFNA’s Occupational Safety & Health Division at 202-628-5465.

[Ryan Papariello is the Fund’s Safety & Health Specialist.]

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