Smoke and Carbon Monoxide Detectors:
Information for homeowners and realtors

Smoke Detectors
Smoke Detectors have come a long way since they were first introduced back in the late 1960's. Smoke detectors can be powered by battery or hardwired into the AC power system in your home and interconnected so that they all sound when one trips. It's important to know the different types and which ones you should have installed in your home:

Ionization Type Smoke Detectors
The oldest type of technology used to detect smoke electronically is the ionization type. Ionization detectors operate by using a small amount of radio active material to induce a charge (or ionize) smoke particles in the air surrounding the detector. When enough charged particles are sensed the detector trips and sounds an alarm. Ionization detectors are good at detecting fires that don't create a lot of smoke (such as small fires inside rooms) but some tests have shown that they do not operate well in smoldering fires that produce a lot of smoke in a short amount of time. Ionization detectors are also prone to false alarms and are often activated by shower steam or smoke from cooking. Up until recently, most consumer level detectors sold were of the ionization variety.

Photoelectric Type Smoke Detectors
Photoelectric type smoke detectors use a beam of light to detect smoke. When enough smoke particles get between the light emitter and the light sensor inside the detector it causes it to alarm. They tend perform well in all types of smoke and aren't as prone to false alarms.

Combination Type Smoke Detectors
Smoke detectors can be made to have both ionization and photoelectric sensors in them. These types are called "combination" type smoke detectors. Another type of combination detector is a smoke/CO type detector that employs either type of smoke detector types in combination with a CO Detector.

What type of detectors should I have in my home?
The type of detectors you should have depends on when your home was built or most recently renovated. Generally homes will fall into one of the four requirement categories below:

My home was built or last renovated before January 1, 1975. What should I have?
Because your home was built before hardwired smoke detectors were required, the code permits you to only use battery powered smoke detectors. Smoke detectors must be the photoelectric type if they are located within 20 feet of a bathroom with a shower or a kitchen. Any Smoke detector located 20 feet or more away from a shower or a kitchen must be a combination photoelectric/ionization type detector. There should be at least one detector on every level of your home and they are generally best located in hallways, at the bases of stairways and outside sleeping areas.

My home was built or last renovated between January 1, 1975 and August 27, 1997. What should I have?
You are required to have a hardwired, interconnected smoke detector for every 1200 sq/ft of living space on each level of your home. They are generally best located in hallways, at the bases of stairways and outside sleeping areas.

My Home was built or last renovated between August 27, 1997 and January 1, 2008. What should I have?
You are required to have a hardwired, interconnected smoke detector with battery back-up for every 1200 sq/ft of living space on each level of your home. In addition you should also have a detector located inside every bedroom. Smoke detectors in bedrooms should be located within 3 feet from the bedroom door, while others are generally best located in hallways, at the bases of stairways and outside sleeping areas.

My Home was built or last renovated after January 1, 2008. What should I have?
You must have hardwired, interconnected smoke detectors that are of the photoelectric type if they are located within 20 feet of a bathroom with a shower or a kitchen. Any Smoke detector located 20 feet or more away from a shower or a kitchen must be a combination photoelectric/ionization type detector. There should be at least one detector on every level of your home and inside every bedroom and they are generally best located in hallways, at the bases of stairways and outside sleeping areas. Detectors located within 20 feet of a bathroom with a shower or a kitchen should be of the photoelectric only type.

What should I do if my CO detector makes noise?
Generally CO detectors only make noise when they detect CO or if there is a problem with the detector such as a low battery. Check your owners manual to know which signal is which. Typically trouble signals present as brief chirps while alarm signals sound continuously. CO detectors are very reliable and do not alarm unless CO is present, so if your detector goes into alarm you should leave the house and call the fire department to investigate. When your detector makes a trouble signal, refer to your owners manual as to the proper action to take.

What should I do if my smoke detector makes noise?
Smoke detectors also make two types of signals, either a trouble signal (if there is a problem with the detector such as a low battery) or an alarm signal. Check your owners manual to know which signal is which. Typically trouble signals present as brief chirps while alarm signals sound continuously. When your detector goes into alarm, check your house immediately for any signs of fire. If there is no fire, the detector may have dust in the sensor that is causing a false trip. Check the owners manual for proper ways to clean the detectors. When your detector makes a trouble signal, refer to your owners manual as to the proper action to take. Smoke detectors are generally only good for about 10 years, so if your detector is that old it may need to be replaced.


Rember to test your detectors monthly and to change the batteries at least twice a year.

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