Will your smoke alarm save your life?

The innovation of smoke alarms is considered one of the most significant improvements to home safety. There is no question that smoke alarms save lives and should be in every home. Ninety-five percent of all homes in America have smoke alarms installed and are required in new construction. We walk past our alarms every day and never give them much thought however, not all smoke alarms are created equal.

About 11 years ago, in the middle of a cold December night we woke to our smoke alarms sounding and a haze of smoke. It wasn’t choking smoke but a grey swirling smoke foretelling something wasn’t right. We never saw a flame but we had an electrical fire in the walls of our home. Fortunately, we were alerted in plenty of time. This was particularly fortunate because, at the time, we had large oxygen tanks in the house for my mother-in laws emphysema. It is no doubt that the smoke alarm in the house saved our lives.

There are two types of smoke alarms available to the consumer, ionized and photoelectric. The type of smoke detector in your home will vastly change your chance of early warning detection depending on the type of fire started. Both look the same but perform very different functions. Let’s look at the alarms and the types of fires.

Ionization Smoke alarms:

This type of alarm works well at detecting small, fast moving particles such as kitchen fires. 95% of homes have Ionization alarms. Fast flame fires are the result of open flame or quick high heat type fires. Kitchen fires or toaster fires would be an example of a fast flame fire. These tend to be intimate fires where people are present or in close proximity to the fire. These types of fires account for a large portion of injuries but a smaller portion of deaths. These types of fires are fast moving and generate small fast moving particles.

Photoelectric Smoke alarms:

Photoelectric smoke alarms do well at detecting medium to large smoke particles. These are very good at detecting dense smoke conditions. Smoldering fires tend to be fires that start slow. This is the type of fire that might start from a heater, electrical fire or a lit cigarette dropped on a couch or mattress. These types of fires my not produce a flame and can burn for long period before detection. Smoldering fires tend to generate a large amount of smoke. Electrical fires may be smoldering inside a wall and go undetected for hours which is what happened in my home. This type of fire accounts for a larger portion of deaths with a smaller portion of injuries. They generate medium to large slow moving particles.

So which one do you need?

On average around 41% of fires start in kitchens, accounting for 15% of fire deaths. Fires in bedrooms, living rooms, family rooms and dens account for about 12% of structural fires but lead to almost 50% of deaths. When we look at these statistics we have to look at why are these fires so much deadlier. Kitchen fires tend to be caused by open flame type fires. (grease fires, burned food, etc.) These types of fires tend to ignite fast and produce a lot of heat and smoke. People are usually present at the time the fire begins and will be more likely to get injured but be able to get out of the house. Fires that start in living rooms and bedroom tend to be associated with upholstery and synthetic foams. This fire will smolder for a long period of time and create large amounts of dense smoke. Due to that fact that this fire smolders for longer periods of time, homes can be filled with choking smoke long before open flames are active. More than half of the injuries from fires are attributed to smoke inhalation, where less than 25% are from burns alone.

As we can see from this information that early warning from smoke alarms become crucial to victim survival. This is where it is valuable to look at the differences between these 2 types of smoke alarms. Data from test performed under different fire conditions show that each type of smoke alarm will perform differently.

According to the National Institute of Standards and Technology that amount of time between first alarm and un-survivable conditions varies by type of alarm and type of fire. In a smoldering fire you have an average of 71.9 minutes until conditions become un-survivable.

An ionization detector, in this type of fire, will take an average 66.8 min. before the alarm will sound giving only 5.1 minutes to escape

A photoelectric detector will sound after an average of 37 minutes providing 34 min to escape.

For fast flame fire’s like kitchen fires there is only an average of 3.6 min. until un-survivable conditions due to the fast moving nature.

An ionization detector will sound after an average of .8 min. providing 2.8 min. to escape.

A photoelectric detector will sound after an average of 1.6 min. giving 2 min. to escape.

Looking at this data tells us that while the ionization type alarm will respond on average sooner than the photoelectric in case of a fast flame fire it responds very poorly in a smoldering fire condition. When we compare this to the information from earlier we see that smoldering fires are attributed to more deaths. With the majority of home using ionization smoke alarms we can deduce that many people are not warned with enough time to escape. So what is the solution? One solution could be to use different types of detectors in different locations in your home. Using an Ionization detector near the kitchen and a Photoelectric detector in other parts of the house could make the difference.

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[icon name=”file-pdf-o” class=”redpdf” unprefixed_class=””] Smoke detectors Q & A Feb 2008

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