In the prior article, we covered the proper maintenance of smoke detectors. One item that we mentioned was that they should be replaced after 5 years. In this article, we will be discussing the different types of alarms and options that are available, including those for the deaf or hearing impaired.
There are two common methods for detecting smoke, which utilizes either the Photoelectric or Ionization system. Each type of unit has its own pros and cons.
Ionization detectors
An Ionization detector contains a radioactive material that ionizes the air, making an electrical path. When smoke enters, the smoke molecules attach themselves to the ions. The change in electric current flow triggers the alarm. These detectors are generally considered more sensitive at sensing small particles. Small particles tend to be produced in greater amounts by hot, flaming fires that are consuming combustible materials rapidly. (i.e. paper burning in a wastebasket, a grease fire in the kitchen)
Photoelectric detectors
A Photoelectric detector contains a light source (generally a bulb that should be changed out every 3 years) and a photocell. When the light from the bulb reflects off the smoke particles, it is directed towards the photocell. The photocell, which is then activated, triggers the alarm. These detectors are best at sensing large smoke particles. Larger smoke particles tend to be produced in greater amounts by smoldering fires, which may smolder for hours before bursting into flame. (i.e. cigarettes burning in couches or bedding, spark from overloaded plug smoldering in a pile of dirty clothes).
Combination Units – the Best of Both Worlds?
Needless to say, the safest idea would be having both kinds of detectors in the house. Well there are actually combination units available that incorporate both ionization and photoelectric technologies and provide early warning for both types of fires. These units will occasionally be listed as Dual Smoke Detectors. With today’s technology and testing this may be the best option for you when you need to replace your existing units.
Battery Powered, Hard Wired, Inter-Connected, Wireless?
- Battery Powered: Most older houses and smoke detectors are battery powered. The major issue with these is that when the battery dies, the alarm does not work. The other problem is that if you are not close to that alarm, you might not hear it.
- Hard Wired: The next iteration was where the detector was connected directly to your houses AC power. (Mandatory for new houses under 1979 IRC) Unfortunately, many of these earlier units did not have a battery backup and if you lost power, or forgot that you turned off the breaker due to a false alarm, the alarm does not work (Battery Backup wasn’t mandatory until the 1991 IRC). The other problem with some of these earlier units is that if you are not close to that alarm, you might not hear it.
- Inter-Connected: Starting with the 1994 IRC, the inter-connected or in-line provision was added which simply means that when one alarm goes off, they all sound.
- Wireless interconnection: If you live in an older house, you can now have a battery powered or hard-wired system that is inter-connected via wireless signals.
Smoke Detectors for the Deaf or Hearing Impaired
Most smoke detectors alert one to a fire by the use of an audible 85-decibel alarm. For those that are deaf or hearing impaired there are a few options that are available to warn you and others of a fire. The first option that is currently mandatory in all Commercial buildings is a smoke detector with a built-in strobe light. While those will work great if one is awake, how about when you are sleeping? There also happens to be smoke alarms perform not only the above functions, but will also make send a signal to specialty watches that vibrate or can connects to a unit that will shake the bed. You can contact the National Fire Protection Association’s Center for High-Risk Outreach at 617.984.7826 for a list of manufacturers and other resources.
Other Specialty Units and Options
- Combination Smoke Detector & Carbon Monoxide Sensor – We recommend having at least one of these in each house, especially in the newer “tight” houses that utilize an ERV or HRV.
- Talking Alarm –This is a nice feature when you have a unit like the one above so you know exactly what the issue is.
- Mute Button – Just in case dinner was a little overcooked, you can mute the unnecessary alarms immediately. These will automatically reset after a set period of time.
- EZ access battery drawer – This is a nice feature so you do not have to remove the detector from the ceiling to change the battery
- Low battery signal mute – I wish mine had this, as it always seems that it won’t start chirping until you are trying to go to sleep & someone used up all the spare batteries. Pressing this button will stop the low battery signal from going off for up to 8 hours
Additional Notes when buying a smoke detector
- Make sure your smoke alarms have been tested and certified for safety by a laboratory. This means that samples of that particular model have been tested under operating conditions and will perform as stated.�
- UL: Underwriters Laboratories Inc. (Most popular in the US)
- ETL: Originally a mark of ETL Testing Laboratories, now Intertek Testing Services.
- CSA: Canadian Standards Association
- CE: Conformance European – meets the EU Specifications
- Check to see if it is easy to maintain and clean.
- Be sure bulbs and batteries are easy to purchase and convenient to install.
- As mentioned above – you should get an “interconnected” system, whether it is hard wired or a battery operated wireless system.
Other Articles:
Smoke Detectors – A primer on Maintenance
Smoke Detectors – A primer on Placement & Location
Everything we owned… Winter Specific Tips on preventing house fires
