Types of Smoke Detectors

smoke detector

During a home inspection, the inspector will evaluate the placement and condition of the smoke detectors in a home.

The NFPA (National Fire Protection Agency) recommends at least one smoke detector (and one carbon monoxide detector) on each level a home. This includes a sub-level or basement.

The home inspector will verify there is at least one detector on each floor of the home and that the detectors are in good condition.

You will need to install a smoke detector on each floor of your home prior to the arrival of the home inspector in order to pass your report.

The smoke detectors should be installed on the ceiling and 4 inches away from the nearest wall. Do not install them directly next to a window or above a stove or chimney fireplace.

There are two different types of smoke detectors to choose from:


An ionization smoke alarm responds well to fires that spark fast. This alarm contains a tiny amount of materials that are radioactive. The materials filter through an air-filled chamber in the alarm. The chamber contains two electrodes with a current between the two. If smoke enters the chamber it will pause the current which will then sound the alarm.


This type of smoke alarm relies on lasers and optics to detect smoke in the air. There is a laser inside the alarm that sends a direct beam across the device. If smoke interferes with the path of the laser it will cause beams to disperse across the device and hit different sensors within the device which will sound the alarm.

The NFPA recommends purchasing combination smoke detectors. A combination smoke detector uses both the radioactive materials and laser sensors for 100% certainty the device will detect the smoke in your home.

The home inspector will verify that the alarm is a combination alarm and recommend the installation of a combination alarm if the home features only an ionization or photoelectric alarm.

You can also purchase a smoke detector that doubles as a carbon monoxide detector. This will save you time and money in having to install multiple detectors on each floor of your home.