Carbon Monoxide

Carbon monoxide (CO) is regarded as the commonest single cause of poisoning in both industry and the home.

Carbon monoxide can kill workers outright. Thousands of other workers suffer from the debilitating effects of high-level exposure, and many many thousands are subject to low-level, long term carbon monoxide exposure, the effects of which are unknown. This poisonous gas is one of the most dangerous and widespread industrial hazards.

Advice for Health and Safety Reps

The key to making the work place safe for all workers is a strong, active health and safety representative and committee. The first step is to identify if carbon monoxide is a hazard in your workplace, and if it is assess the risk and then go to the employer to discuss the elimination or control of that risk.  Use the information below to assist you.  If you need assistance, contact your union.

Controlling the Hazard

The best way to control carbon monoxide exposure is to remove it entirely from the environment. This can be done by substituting non-gas producing equipment, such as battery powered engines, for vehicles or machinery that emit carbon monoxide. Ventilation systems are another effective means of eliminating carbon monoxide from the environment. Individual operations can be enclosed and hooked up to a local exhaust system. Portable exhaust devices can be employed to remove gas from enclosed or underground work areas. Keeping equipment in proper working order will also minimize potential hazards.

As a last resort, workers can be provided with protective respiratory equipment. And, of course, the employer should provide workers with information and training in the potential hazards and the treatment of carbon monoxide poisoning.

Legal Standards

The current Australian standard set by Safe Work Australia limits exposure to 30 parts of carbon monoxide per million parts of air averaged over eight hours, or 34 milligrams per metre cubed. This standard applies in Victoria. Regulation 166 of the OHS Regulations 2017, requires the employer to undertake atmospheric monitoring:

Atmospheric monitoring

1.  An employer must ensure that atmospheric monitoring is carried out in relation to a hazardous substance supplied to or generated at the employer's workplace if there is an exposure standard for the hazardous substance or any of its ingredients and—
   
   

   (a) there is uncertainty (based on reasonable grounds) as to whether the exposure standard is or may be exceeded; or
   (b) atmospheric monitoring is necessary to determine whether there is a risk to health.

2. Subregulation (1) does not apply to a hazardous substance if health monitoring is required for the substance under regulation 169 and the health monitoring includes biological monitoring.          

Note: Act compliance—section 22(1) (see regulation 7).       

Remember though, that standards are generally set at a level that experts believe "most" people should not be adversely affected, and do not take into consideration personal health problems or strenuous work situations. Persons with heart trouble or respiratory ailments such as asthma or emphysema may be endangered by carbon monoxide at a lower threshold than that allowed by the standard. Any worker performing strenuous tasks that cause heavier than normal breathing will take in large quantities of carbon monoxide. Smokers, who may already have carbon monoxide in their blood from inhaled smoke, may feel adverse effects of carbon monoxide poisoning more quickly than non-smokers.

Information on Carbon monoxide

The main danger with carbon monoxide is that it cannot easily be detected. Carbon monoxide is a colourless, odourless and tasteless gas, so it doesn't give its victims any advanced warning. Carbon monoxide comes from the incomplete burning of petrol, wood, coal, oil, propane, gas or anything else that contains carbon. The poisonous gas consists of only two elements, carbon and oxygen, and mixes easily with air. Poisoning occurs from breathing in the toxic compound from the air.

Industries and processes where CO is a potential hazard include furnaces, kilns and foundries, catalytic cracking units in petroleum refineries, fire-fighting, and the manufacture of certain chemicals including formaldehyde and synthetic methanol. Carbon monoxide is present in the exhaust gas of internal combustion engines, and motor vehicles are responsible globally for the majority of human-made CO emissions. Truck drivers, forklift operators, or anyone working near such equipment are exposed. Particularly in danger are persons working near enclosed areas such as manholes, garages, tunnels, warehouses, and vehicle repair shops. In the domestic environment, heating, including space and combustion heaters, is also an important source of CO.

Health Effects

Carbon monoxide enters the bloodstream through the lungs and combines with haemoglobin. Haemoglobin is the red part of the blood which carries the oxygen. Although carbon monoxide follows the same path as oxygen, the poison gas combines with haemoglobin 210 times faster than oxygen. This means that even though there may be plenty of oxygen in the surrounding atmosphere, carbon monoxide will get into the bloodstream first. High blood level concentrations of the carbon monoxide will prevent sufficient amounts of oxygen from reaching the heart and brain. This can lead to suffocation, capillary haemorrhaging, permanent damage of nerve tissues and brain cells, and even death.

The initial symptoms of carbon monoxide poisoning are difficult to differentiate from other possible causes. Low-level exposure can cause headaches, dizziness, drowsiness or nausea. Further exposure will aggravate the preliminary symptoms and can be accompanied by a rapid pulse, confusion, loss of coordination, or collapse. Finally, high exposure can lead to convulsions, coma, or death. A highly exposed victim who recovers may still suffer permanent damage of the brain or nerve tissue.

Sudden exposure at high levels, however, can kill in just a few minutes. During World War II in Italy, over 500 persons were killed almost instantly when their overloaded train became stuck in a steep, icy tunnel and toxic gas from the burning coal suffocated them.

The long-term effects of low-level exposure are uncertain. Pregnant workers may face a special danger, although low-level carbon monoxide exposure has not been linked definitely to birth defects. Cases of extreme poisoning, however, have resulted in still-births or nervous system defects in newborn children.

Workers with health problems, such as heart trouble, anaemia, or respiratory ailments affecting the flow of oxygen in the bloodstream, may be more readily endangered by carbon monoxide exposure than workers without such conditions. Because carbon monoxide is a by-product of cigarette smoking, smokers may be adversely affected by the gas more quickly than non-smokers. Carbon monoxide exposure can also contribute to pneumonia by allowing the entry of saliva or foreign matter into the respiratory tract.

Medical Treatment

Regardless of the level of exposure, practically all carbon monoxide is eliminated from the bloodstream within eight to ten hours after exposure ends. Once carbon monoxide is detected, workers in the contaminated area should be removed immediately.

Acute poisoning can be treated by restoring breathing with artificial respiration or resuscitation equipment. The removal of carbon monoxide from the haemoglobin is accelerated by the inhalation of oxygen. The victim should be kept lying down and warm in an area away from draft. The after-effects of carbon monoxide poisoning should be treated by a physician and the victim may need hospitalisation.

See also:

• The SafeWork Australia Exposure Standard and information.
• Frequently Asked Questions on Carbon Monoxide (from UK's HSE website)
• General information from a number of sources from a very useful website, Medline Plus

Based on a hazard sheet prepared by the Canadian Auto Workers Union.

Last updated March 2022

Important Chemicals Information