Avoid Toxic Fumes in your Garage

Avoid Toxic Fumes in your Garage

With recent news reminding us just how much damage carbon emissions have done to our atmosphere, it’s timely to think about their effect on our home environment. If your car is housed in a garage, carbon monoxide (CO) gets released into the garage every time you start the car and each time you park. 

Let’s look at the dangers of CO and steps you can take to reduce the concentration of toxic fumes in your garage.

Carbon monoxide (CO) is a toxic gas that human senses cannot detect, it is odourless and colourless. It’s found in combustion (exhaust) fumes produced by:

Gas heaters • fireplaces • car mufflers • space heaters • gas and charcoal bbqs • car engines • portable generators

Everyone is exposed to small amounts of carbon monoxide throughout the day. However, inhaling too much of it can cause CO poisoning.


Buckle them in, then start the car and exit the garage immediately.

The typical internal combustion engine used in most cars and trucks produces high concentrations of CO. Emissions have been dramatically reduced by changes in engine design, fuel, and emission control devices such as catalytic converters, which can decrease the amount of CO in the exhaust fumes from 3.5 to ca. 0.5% source

However, operating a motor vehicle still puts you at risk from carbon monoxide poisoning.

CO can increase to dangerous levels when combustion fumes become trapped in a poorly ventilated or enclosed space (such as a garage). Inhaling the fumes causes CO to build up in your bloodstream, which can lead to severe tissue damage.

Warming your car up while in the garage - even for two minutes - produces toxic amounts of carbon monoxide. That dangerous gas tends to remain in the garage, taking a long time to dissipate and in the case of attached garages, leaking into other areas of the home. 

DO's - to reduce exposure to harmful carbon monoxide

• Reduce carbon monoxide production. Limit the amount of time you let your car sit and idle in the attached garage. 

• Ensure everyone is inside the car with doors closed before starting the engine

• Open the garage door, start the engine and exit the garage immediately

• Keep internal access doors closed

• Open doors and windows on all sides to allow breezes to clear accumulated gas

• Take lawn mowers, leaf blowers and other equipment outside to start them

• Install a CO detector in the house - not in the garage

• Keep gas and charcoal barbecues away from the house


Keep bbqs and outdoor heaters outside and away from open windows.

In winter especially, you may be tempted to warm the car up in the garage, but that is a dangerous habit to get into. Thomas Greiner, an extension agricultural engineer from Iowa State University, has this warning. "Don't ever warm-up a car in a garage, even with the garage door open. In less than two minutes gas fumes can build to lethal concentrations in the garage.” In an attached garage, fumes can quickly spread to the house.

Cold engines produce higher concentrations of carbon monoxide and produce it for longer periods of time. 

When the engine is cold, the fuel mixture is rich (causing more CO), and the catalytic converter is  ineffective, unable to convert deadly CO to carbon dioxide (CO2). Even well-tuned engines will produce over 80,000 parts per million for the first minute or two of operation.

Concentrations so large fill the garage with carbon monoxide in a very short time even with the door open. Once the car is backed out of the garage and the garage door closed, large concentrations of gas still remain trapped in the garage. In a house built with an attached garage, part of the gas then seeps into the house where it remains for hours.

CO is a silent killer, tragically claiming the lives of a mother and her three young children in Ashburton in 2015.

Carbon monoxide reduces the oxygen supply to the brain, causing CO intoxication, and lack of reasoning. At high concentrations such as produced in the exhaust of a cold engine, intoxication occurs in only a few minutes, leaving those poisoned incapable of realising they are poisoned and unable to protect themselves. 

Carbon monoxide poisoning can happen to anyone, although children, the elderly and those with health concerns are especially susceptible.


Could your garage be this bad?

DONT's - ignoring the risks can be fatal

• Do not warm your car up in the garage

• Do not leave your car running in the garage, even if the garage door is open

• Do not ride in the back of a ute with a canopy

• Do not swim behind an idling boat

• Never use outdoor cooking equipment indoors, for any reason

• Never operate a portable generator indoors, or close to a home

• Never use outdoor appliances as an alternative heat source indoors

It takes just a little forward-thinking and a bit of extra effort to make a big difference with carbon monoxide. We think you're worth it. Take a look at the full report by T.H. Greiner, Ph.D., P.E Extension Agricultural Engineer.

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