Carbon Monoxide in Indoor Air

Carbon monoxide (CO) is an odourless, colourless gas that is a by-product of combustion. The main sources in homes are smoking, fuel-burning appliances and infiltration of vehicle exhaust from attached garages or outside. The health effects from CO can be very serious.

What are the health effects of carbon monoxide?

When you breathe in carbon monoxide it binds with a protein in your blood called haemoglobin and reduces the ability of the blood to carry oxygen throughout the body. The symptoms of carbon monoxide poising get worse as CO levels and exposure time increase. At low levels, symptoms include headaches, tiredness, shortness of breath, and impaired motor functions. These symptoms sometimes feel like the flu. At high levels, or if people are exposed to low levels for long periods of time, people can experience dizziness, chest pain, tiredness, poor vision, and difficulty thinking. At very high levels, carbon monoxide can cause convulsions, coma, and even death.

Carbon monoxide levels in Canadian residences with properly functioning fuel-burning appliances are usually well below the limits recommended by Health Canada.

How do I prevent carbon monoxide from building up in my home?

To protect you and your family from carbon monoxide follow these simple steps:

• Make sure that all fuel-burning appliances such as furnaces, fireplaces, gas stoves and water heaters are well-maintained and working properly. Have your appliances inspected by a professional at least once a year and be sure to use a ventilation hood for gas stoves.
• Never use a barbecue indoors, and don't use kerosene or an oil lamp in enclosed areas unless they are specifically designed for indoor use.
• Don't let vehicles idle in the garage, especially when the garage door is closed. Also, keep the doors between your house and the garage closed. Never run gas powered lawnmowers, trimmers, or snow blowers in the garage.
• Since tobacco smoke is a source of carbon monoxide, don't let people smoke in your home.
• Purchase a CSA-approved carbon monoxide detector and place it where you can hear the alarm.

The  Canada Mortgage and Housing Corporation (CMHC) also has information on carbon monoxide in the home and proper maintenance of fuel-burning appliances.

What are Health Canada's recommended limits for carbon monoxide?

Health Canada's Residential Indoor Air Quality Guideline for carbon monoxide recommends maximum exposure limits of:

• Short-term exposure: 25 parts per million (ppm) based on a 1-hour average
• Long-term exposure: 10 parts per million (ppm) based on a 24-hour average

The short-term limit is meant to prevent the immediate health effects that may occur from exposure to CO for a limited period of time (e.g. 1 hour). The long-term exposure limit protects against health effects that may develop following extended exposure to CO (e.g. 24-hours).

Health Canada's recommended limits are set to protect sensitive individuals, such as those with pre-existing heart problems from extra stress on their hearts and lungs due to CO exposure. The most serious effects of carbon monoxide poisoning will occur at levels much higher than Health Canada's guidelines.

Will a carbon monoxide detector protect my family from carbon monoxide?

Installing a carbon monoxide detector with an audible alarm is a recommended safety precaution. Only those detectors bearing the Canadian Standards Association (CSA) certification mark should be purchased and these must always be installed and maintained in accordance with the manufacturer's instructions. For more information, consumers can visit Health Canada's Consumer Product Safety.

Carbon monoxide detectors are designed to prevent acute (immediate) carbon monoxide poisoning and are set to sound an alarm at levels significantly above Health Canada's exposure limits. Most detectors do not sound alarm until levels are above 70 ppm for 1-4 hours. Long-term exposure to CO levels below this level may affect health, especially for sensitive individuals, including the elderly and individuals with heart problems. A carbon monoxide detector can provide additional protection, but it is not a substitute for proper installation and maintenance of combustion appliances.

What are the Residential Indoor Air Quality Guidelines?

The Residential Indoor Air Quality Guidelines are Health Canada's official position on the health risks posed by an indoor air pollutant, based on a review of the best scientific information available. They summarize the known health effects, describe indoor sources and levels, and, provide a recommended exposure level below which health effects are unlikely to occur. The Guidelines are recommendations only and are not an enforceable standard under any regulation. They are meant to serve as a scientific basis for activities to reduce the risk from indoor contaminants. This could include the development of regulations or standards or the production of communication materials aimed at the general public.