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The dead of winter is the peak season for carbon monoxide risks; that’s when all your gas-fired appliances work overtime. We all know that carbon monoxide asphyxiation can spoil your whole day, but for some people, chronic low-level exposure can be a problem too.

As Indoor Air Quality Experts in Calgary, we have information to be aware of regarding Carbon Monoxide risks.

Why It’s So Dangerous

Carbon monoxide (CO) is a colourless, odorless gas produced whenever you have incomplete combustion of a carbon-based fuel. CO molecules bind to the hemoglobin in your blood, taking up the bonds that normally carry and release oxygen. If your blood takes up too much CO, it doesn’t matter how much oxygen is around you; your blood can’t carry that oxygen to your cells, and your tissues eventually suffocate.

Levels of carbon monoxide exposure are expressed in Parts Per Million (ppm). To give you some perspective, here’s a list of levels and their effects:

  • 0 – 9 ppm: common indoor levels with no health effects
  • 50 ppm: maximum permissible exposure in the workplace
  • 100 ppm: headache after 1 or 2 hours
  • 200 ppm: headache, dizziness, nausea & fatigue in 2 or 3 hours
  • 400 ppm: headache, nausea etc. after 1 hour, life threatening in 3 hours
  • 800 ppm: unconsciousness in 1 hour, death in 2-3 hours
  • 1600 ppm: unconsciousness and death in 1-2 hours
  • 3200 ppm: unconsciousness in 30 minutes, death within 1 hour
  • 6400 ppm: unconsciousness in a few minutes, death within 30 minutes
  • 12,800 ppm: near immediate unconsciousness, death within 1-3 minutes

Chronic carbon monoxide exposure above 10 ppm may have long-term health consequences, and transient exposure over 50 ppm must be investigated and acted upon.

Why It Happens

Carbon monoxide trouble was frequently associated with fireplace usage– if you have an older wood burning fireplace, do take care to crack open a window when you use it– but new fireplaces these days are sealed combustion units that breathe on their own.

More commonly a furnace heat exchanger may crack, or perhaps furnace exhaust vents and fresh air intakes may become plugged up with snow, frost or debris. The latter is a common cause of sudden shutdowns of furnaces and water heaters, as modern gas appliances are designed to shut down if they can’t breathe properly. An efficient, properly running furnace might routinely produce up to 8 ppm of CO; poor combustion could raise that to several hundred ppm.

We encourage you to keep your furnace filter clean, be sure exhausts and intakes are clear, and have your gas appliances checked and serviced annually.

Low Level Exposure

If you’re feeling tired and run down in the winter– maybe suffering from persistent headaches– and you don’t have a cold or the flu, you may be experiencing the effects of low-level carbon monoxide in the range between 10 – 70 ppm. Do you find yourself feeling suddenly groggy when you’re at home, while perking up anytime you leave? If so, it’s time to investigate whether there’s a toxic situation in your house.

Some common activities that contribute to low level CO exposure are smoking, burning candles or incense, open fireplaces, and extended use of gas fired ranges.


More serious carbon monoxide poisoning is very dangerous, and rapidly affects one’s judgment. You cannot rely on your own senses to determine whether there’s a problem!

Make sure you have working CO detectors in your home. We recommend placing a detector near your furnace or water heater, and in hallways outside of sleeping areas (this is standard procedure we follow for new furnace installations).

Good quality detectors are available at any home supply store under names like Kidde, Night Hawk, and First Alert, but any CSA-approved detector will suffice. Be aware that these don’t alarm at levels below 30 ppm, because CO concentrations from 10 – 30 ppm can commonly be reached during chinook conditions, temperature inversions, smoke from wildfires, or near busy traffic intersections.

Early commercial detectors produced a lot of false alarms; the rationale for no alarm under 30 ppm is to limit 911 calls in cases that are not emergencies.

Canadian Standards

Here’s a quick summary of the current CSA standard for carbon monoxide alarms:

  • At 0–29 ppm, the detector must remain silent
  • At 30–69 ppm, the alarm may sound after 30 days
  • At 70–149 ppm, the alarm must sound within 4 hours
  • At 150–399 ppm, the alarm must sound within 50 minutes
  • At 400+ ppm, the alarm must sound within 15 minutes

The takeaway here is that your CSA-listed carbon monoxide detector will warn you of an immediate threat to your life, but not necessarily chronic low-level exposure. For example, the Alberta OHS limit for CO exposure in the workplace is 25 ppm over an eight-hour shift; a commercial detector will not alarm at this level. The transient exposure limit is 50 ppm, at which your detector could take 30 days to sound an alarm.

Give Us A Call!

If you’re concerned about possible health effects from chronic low-level exposure between 10 – 70 ppm, you may want to supplement your standard CO detectors with a visit from one of our journeyman gas fitters. We have sensitive testing equipment that can detect lower levels of carbon monoxide in your home and ample experience to ascertain the source.



George Pinel
George Pinel

Master Plumber

I have been involved in this family owned business for 33 years now.

It has always been and will continue to be the core focus of Instant Plumbing & Heating to provide a long lasting relationship with our customers based on trust and integrity of our service and products.

This achieved by using the best quality materials. I as a business owner continue to mentor and treat my staff with the highest regard and respect, this interns helps them deliver to the client great quality workmanship and service.

It is our professional goal to leave a situation better than when we arrived both in how we do our work and in how you feel for having chosen us to do your work, we are in the anxiety reduction business using plumbing and heating service work to do it.

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