Carbon Monoxide – A Home Inspector’s Perspective

by Mar 4, 2020

Carbon Monoxide (CO), also known as the silent killer, is indifferent. It doesn’t matter whether you live in Yorkville, Oswego, Aurora, St. Charles, Batavia, Geneva, surrounding Chicagoland communities, or anywhere else.  CO is a colorless, odorless, tasteless gas created from the incomplete combustion of fossil fuels. Natural gas, propane, gasoline, diesel, oils, coal, and wood are all fossil fuels. Cars, fireplaces, and household appliances such as water heaters, furnaces, dryers, and stoves burn fossil fuels.  All of these can create carbon monoxide under the right conditions.  Inhaled CO displaces the oxygen needed by your body, resulting in carbon monoxide poisoning. Even low levels of CO can cause flu-like symptoms. High levels can cause death – quickly.

How can you prevent CO poisoning?

Always keep your car and household appliances in proper working order to help prevent the buildup of carbon monoxide. But what if your car or appliances are not working properly and one of them creates CO?  Is there a safeguard to help warn you of this condition?  Yes! We have carbon monoxide alarms.  These, along with smoke alarms, are like insurance policies. They are there when you need them.

The History of CO Detection


Late 1700s:
CO First Discovered

We didn’t know about the toxic effects until years later.  Once we knew about those toxic effects, we realized the need for CO regulations and alarms in both commercial and residential settings.

Early 1900s:
Introduction of the First CO Detector

It was a far cry from the type we use today.

First Battery-Powered CO Alarm

The Consumers Products Safety Commission (CPSC) and Underwriter Laboratories (UL) said that the device had to sound an alarm long before it detected dangerous levels of the gas.

Mid to Late 1990s:
Growth of Usage

Residential use grew during this period, mostly due to code and laws dictating it.

January 1, 2007:
Illinois Carbon Monoxide Alarm Detector Act Goes into Effect

The Illinois Carbon Monoxide Alarm Detector Act requires homeowners, landlords, and building owners to install carbon monoxide detectors within 15 feet of rooms used for sleeping. The age of the structure doesn’t matter. This law applies if you use fossil fuel to cook, heat, or produce hot water. It also applies if you have a connected, enclosed garage. The CO detector must have the label of a nationally-recognized testing laboratory. It must also comply with the most recent standards of the Underwriters Laboratories.

How does a CO alarm work?

CO alarms work on a weighted basis. The lower the level, the longer it will take for the alarm to sound. When alarms first came to market, the threshold level was set low (non-dangerous levels), which caused a lot of nuisance alarms. These alarms resulted in useless fire department trips to residences. Manufacturers eventually raised threshold levels.

Where should you install a CO alarm?

Urban legend says you should install carbon monoxide alarms low on a wall. It actually doesn’t matter. CO is about the same weight as air and distributes evenly throughout a room. Although Illinois says the alarm should be installed within 15 feet of a room used for sleeping at 15 inches below the ceiling, it is good practice to put one near any gas-burning appliance in a house.

Life Expectancy of a CO Detector

Originally, sensors had a life expectancy of five-to-seven years. That’s why manufacturers recommend that the older type be replaced at five years. These sensors can become unreliable.

According to Kidde, their sensor technology improved in 2013. Most of their CO detectors now have a life expectancy of 10 years. Also, most detectors come with 10-year sealed batteries, which extends the usable life. The benefit of this new battery life is that you don’t have to worry about replacing the batteries every year or so.

You should test your CO detector once per month. Be aware, though, that the test button only tests the battery and alarm, not the CO sensor itself.  To the best of my knowledge there isn’t a way to test the CO sensor the way you can create smoke to test a smoke. (To learn more about smoke alarms and detectors, click here to read my previous blog on that subject.)

What to Do If Your Alarm Sounds

From 2003 to 2010, U.S. fire department responses for CO increased from 40,000 to over 80,000. This was mostly due to the increased use of carbon monoxide alarms. The Center for Disease Control and Prevention reports 20,000 visits to the emergency room, 4000 of which result in hospitalization, due to carbon monoxide poisoning, and 400 deaths per year.

Actions that create cause carbon monoxide include heating your home with a gas range, not opening the fireplace flue, burning charcoal and running your car, lawn mower or snow blower in an enclosed area. Other causes include exhaust gas spillage, (commonly called backdrafting) from furnace and water heaters or damaged fireplace flues.

The best thing you can do is train your family so they’re aware of what to do when the alarms sounds. If an alarm goes off, follow these guidelines:

Is there is just a chirping sound?

That means the battery may be low and in need of replacement. Follow the manufacturer’s instructions on maintenance and testing for next steps.

Do you feel ill?

  1. Get everyone outside.
  2. Take a headcount to make sure everyone made it out.
  3. Call 911.

Do you feel OK?

  1. Push the reset button. If it goes off again after a short period of time, assume it’s a CO event.
  2. Get everyone outside.
  3. Take a headcount to make sure everyone made it out.
  4. Call 911.

Carbon monoxide events can be intermittent so don’t dismiss them. You can contact us or a BPI building analyst to determine why you get ongoing false alarms.

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