CARBON MONOXIDE DETECTORS
The life expectancy of a carbon monoxide detector which is part of a security system is approximately 5 to 6 years. After this period of time, if carbon monoxide is present, there is a good chance that the unit will not be able to detect the gas.

Depending on the brand, notification of sensor failure is different. Some units have the expiration date written on a label under the cover. Other units have a combination of visual notification and chirping.

It is not a bad idea to be proactive and if your units are 5 years old, have the sensors replaced.

SMOKE DETECTORS
Smoke detectors have a life expectancy of 10 – 15 years and when they fail, have a tendency to false alarm. Commercial fire alarm systems are required to have their systems inspected at least once a year by a licensed contractor in accordance with NFPA standards. No such requirement exists for residential fire alarms, but it is highly recommended that these systems be checked for proper operation as well.