How Carbon Monoxide (CO) Detectors Work
CO detectors measure CO levels in the environment and sound an alarm
to warn you to ventilate the affected area.
Two basic types of CO detectors
CO detectors are either battery operated or electric. Most CO detectors
on the market use one of the following three sensor types.
1. Electrolytic Sensor Detectors - This type of sensor is extremely
sensitive to detecting CO in the home. Although it is the most efficient
type of CO detector, it is rarely used due to its significant cost.
2. Colorimetric Sensor Detectors – This type of sensor
measures the build-up of CO over time. Once the alarm has been sounded
it takes up to 48 hours to reset.
3. MOS Detectors (Metal Oxide Semiconductor Sensor) – This
type of sensor is very popular because it can detect other gases besides
CO such as chlorine bleach and silicones.
CSA and UL-Approved Devices Change
As of 2010 both the CSA and UL standards prohibit a CO detector from sounding
the alarm at relatively low levels. This change was made to reduce the
amount of false alarams that fire departments were dealing with as a result
of detectors with low level settings. There are low-level detectors commerically
available, however these units are not certified by the CSA or the UL.
Currently, CSA and UL-approved devices will be set to sound the alarm
at CO concentrations above 70 ppm. This is significantly higher than the
exposure levels recommended by government health guidelines.
CO fire detectors
These electronic detectors sound against a fire by sensing CO levels in
the air. They should not be confused with CO detectors used to protect
people from CO poisoning.
- CO fire detectors are effective for deep-seated, smoldering fires.
- Smoke detectors are better at reacting to smoke that rises.
Choosing a Battery Operated or Electric CO Detector
You may be wondering whether to purchase a battery operated CO detector
or one that runs on a household electric current.
There is no difference in cost between the battery operated and the electrically
run CO detector.
- The battery operated type is easier to install and can be placed
anywhere in the house.
- The electric type can only be installed near an outlet or hard wiring.
- The electric type requires no maintenance.
- The battery operated type needs periodic maintenance such as changing
the battery every year.
Exposure display feature
- The electric type uses a solid-state sensor that purges itself
and re-samples for CO continuously keeping you up to date on the CO
levels in the house.
- The battery operated type uses a passive sensor that reacts
to the prolonged exposure to CO gas.
- The electric type resets immediately after the CO problem has been
- The battery operated type must be manually reset. This may involve
removal of the sensor pack. The reset time will depend on concentration
and duration of the CO exposure.
- The electric type will not work during a power outage unless equipped
with a battery backup.
- The battery operated type can be depended on in during an outage
or any emergency, as long as the battery is charged.