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Smoke Alarm vs. Carbon Monoxide Alarm

December 19, 2018

Smoke Alarm Detector


Statistics show that 30% of smoke alarms in North America are not maintained. Smoke alarms (also called smoke detectors) have been in widespread use since the late 1960’s and in the last few decades are required in all new homes and in some cases fire codes have required retrofitting them into homes. Recognizing smoke alarms are a requirement in a home inspection, but how do you know if yours is working?

What is the Difference between a Smoke Alarm and a Carbon Monoxide Alarm?

Both smoke alarms and carbon monoxide alarms are important life saving devices in your home, but they behave in a totally different manner.

Smoke Alarm

The primary function of a smoke alarm is to detect the early stages of a fire in the home and to alert the residents while they still have time to get out safely. The dangers of not having a smoke alarm are burns, suffocation, both leading, in the worst case scenario, to death.


Carbon Monoxide Alarm

A CO alarm measures the amount of CO gas in the home’s air and alerts residents when the levels are too high. CO is colorless, odorless and has an increasing effect on health. The health hazard of not having a CO detector is dizziness, headaches, nausea, and in the worst case scenario, convulsions, and death.

Combination Alarm

This alarm, includes both a smoke and CO detector in one device.

Where does Carbon Monoxide come from?

Carbon Monoxide is an ordinary exhaust gas from burning fuels. It is created in our homes by furnaces, boilers, and hot water tanks as well as gas ovens, car exhaust, and gas fireplaces. CO gas spreads equally in homes so alarms need to be placed on all living areas and mainly near bedrooms.

A professional home Inspector will inspect venting on utility equipment, fireplaces, and kitchen cooking equipment as well as look for an air tight seal between the house and garage. Nevertheless, not all CO defects are visible in an inspection and CO can occur at any time due to a system failure. Having a CO detector in your home is an excellent way to protect yourself and your family from this colorless and odorless gas.

Why Does My Smoke Alarm Always Go off When I’m Cooking?

There are two common types of smoke detectors.


This type of alarm uses an air ionization process to electrically measure smoke in the air. The earliest signs of fire are immediate and while this is possibly an annoyance near kitchens due to false alarms from burning food, it is a benefit near bedrooms when people need the most warning of a fire to get out safely.


This type of alarm looks for smoke hovering in the air. If you are suffering from false alarms due to cooking, replace the smoke detector with one of these alarms. Some alarms also have a silence button to silence false alarms. Never remove the battery from a smoke alarm or you risk not having a working alarm in a real fire.

Where Do I Need to Install Smoke and CO Alarms?

Codes for this vary by municipality, but smoke alarms should be at minimum on every level of the home and outside of bedrooms. idyllically, they should also be in every bedroom.

At minimum, a CO detector should be located near bedrooms yet the best recommendation is to have one on every level of the home and in each bedroom. Since the best procedure is to have both a smoke and CO alarm in all bedrooms, this is simply done with a combination smoke/CO alarm in each bedroom.

Batteries and Life Cycle Replacement

30% of smoke alarms installed in residential properties are not maintained correctly and this is primarily due to unit age and battery life.

Every 10 Years

The measurement equipment in smoke alarms deteriorates over time and as a result, and they need to be replaced every 10 years. Alarms with square 9-volt batteries should have batteries changed annually. A good way to remember this is to do it with the changing of your clocks for daylight savings time. Many newer smoke alarms have incorporated 10-year batteries which make them maintenance free as long as they are replaced every 10 years. Some smoke alarms are hard wired to the home or an alarm system so they never need batteries; Nonetheless, the alarms themselves still need changing every 10 years.

Every 7 Years

CO detection equipment last only 7 years. 

These units are generally run at power outlets which don’t need batteries changed, but there are battery operated detectors which require batteries changed about every year.

If you are having a home inspection done, your home inspector should be looking for smoke detectors at each level of the home and outside of bedrooms. Unfortunately, home inspectors cannot open alarms to confirm the alarm age or battery quality so always plan to replace batteries on move in day. In addition, check the date stamp on the equipment at that time to see if it needs replacement. CO detectors may be portable and many occupants take them when they leave. If so, buy CO detectors for your new home and install them on move in day.


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