smoke alarms Archives - Cities Inspection Service

Most people assume a smoke detector is a smoke detector…this is not true.

In the mid 1970’s less than 10% of homes had a smoke detector; now over 90% do. Nevertheless, this dramatic increase in smoke detectors has had little impact on the risk of death by fire. Why? Some studies have indicated that many smoke detectors are either inoperable or have been disabled. Nuisance alarm activations are a major reason why detectors are disabled. National Fire Protection Association, NFPA, studies have indicated ionization alarms account for over 95% of all nuisance alarms.

Another reason is the age of the smoke detector. All smoke detectors should be replaced every 10 years.

What are the statistics on ionization vs. photoelectric smoke detectors?

The majority of residential fire fatalities are due to smoke inhalation. Ionization detectors respond an average of 15 to 50 minutes slower than photoelectric. Some studies indicate they completely fail to work 25% of the time. However, ionization detectors respond faster in fast flame fires. Studies show 30 to 90 minutes quicker than photoelectric. Certainly, either smoke detector is better than none at all. Of course, a functioning smoke detector is most important. But if time and reliability are vital to our chances of surviving a smoldering fire, a photoelectric smoke detector is the best type to install in your home.

Less than 10% of all smoke detectors in homes are photoelectric.

Doug Hastings
MN Home Inspector, Minneapolis & St. Paul
ASHI Certified Inspector, ACI
Kaplan University, Home Inspection Lead Instructor

In a fire, the issue is time.

Minutes and many times seconds will make the difference between life and death. The combustible materials in our homes are different from the past and the technologies of smoke detectors have also changed. There are two types of smoke alarms, ionization and photoelectric. 90% of homes have ionization smoke detectors installed; about 5% are photoelectric and the rest have no alarm at all. The type of smoke alarm can be the difference between your family getting out of the house in time or not.

To better understand the importance of this; there are two types of residential fires, ‘fast flame and smoldering’. The vast majority of residential fire fatalities are due to smoke inhalation from a smoldering fire. And almost two-thirds of these fatalities occur at night while the occupants are sleeping. Photoelectric smoke detectors are by far the best for smoldering fires. Ionization detectors are very slow to respond to smoldering fires. Actually, Ionization detectors have proven to be significantly less reliable in both ‘fast flame and smoldering’ fires.

What type of smoke detectors do you have in your home?

Daylight saving time is a great time to change the batteries in your smoke detectors. This year you should also examine the label on the back of your detectors. If the label says anything about radioactive material, Americium 241, or model number has an “I” then it is ionization. You should replace these detectors with photoelectric. More facts will be in next week’s blog.

All smoke detectors are not alike. Make sure you are protecting your family with the best fire alarm possible.

Doug Hastings
MN Home Inspector, Minneapolis & St. Paul
ASHI Certified Inspector, ACI
Kaplan University, Home Inspection Lead Instructor

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Are All Smoke Detectors Alike?