Fire Alarms and Carbon Monoxide Alarms

Let’s talk smoke alarms.  Smoke alarms are missing in 30% of home fires.  About two-thirds of the deaths in home fires are in homes that either didn’t have a smoke detector (40%) or didn’t have a working smoke detector (23%) (source).

Things everyone should know about smoke alarms:

There are two types of detectors

There are two types of smoke detectors, ionization detectors and photoelectric.  Both types are effective and need to pass the same standards to be UL listed.  Ionization detectors react faster to quick burning, small particle fires while photoelectric respond faster to smoldering fires.  In general, I think it’s a good idea to have a mix of types, new alarms even come with both detector technologies integrated in one unit (example).

Ionization Alarms

The ionization alarms work by using a small amount of radioactive material to ionize the air between a pair of plates.  The ionized particles migrate to the two plates creating a small electrical current.  When smoke enters the ionization chamber, it reduces the amount of ionized particles that can reach the two plates.  This creates a current drop which sets off the alarm.

Photoelectric Alarms

Photoelectric alarms work by shining a light through a tube that looks like a “T”.  The light goes through the “top” of the “T”, when smoke enters the chamber, it causes some of the light to reflect down towards the “base” of the “T”.  A light sensitive sensor on the base of the “T” is triggered when enough light bounces down.

Smoke alarms expire

That’s right, smoke alarms have an expected life of 10 years.  If you pop  the alarm off of the wall it should have a manufacture date.  Smoke alarms are cheap, if you’re past the 10 year date, it’s time to buy new ones.

Where should I put them?

FEMA, and the Washington State Fire Marshall recommend placing smoke alarms “near each sleeping area and on each level of your home.”  In my home, I have one in each bedroom and in every hallway.  The bedroom units are ionizing, the hallway units are dual sensor.

Hard wired or battery operated?

In general, if you have the option for hard wired alarms, that’s a better choice.  Hard wired alarms receive line power as well as have the battery backup.  They also have the advantage of being linked together which means if one goes off, they’ll all go off.  This enhances the odds of safely getting out of the house.  For hard wired alarms, I recommend this one: Kiddie dual sensor wired alarm,  I like it because it’s inexpensive and has both types of detectors.
If, like me, you don’t have the option of wired alarms, there are plenty of sound battery operated ones.  I recommend this one: Kiddie dual sensor battery alarm.  This is the model I have in my hallways, it’s inexpensive and has both types of detectors.

Lithium-Ion batteries

A neat trick you can do is to use a lithium-ion 9-volt battery instead of a normal one in your smoke alarm.  These have a 10 year lifetime.  This doesn’t get you out of regularly testing your battery but it does mean you won’t be woken up in the middle of the night because the battery is dying.  They’re more expensive than the alkaline, but cheaper in the long run.

The test button doesn’t actually test the detector

The test button on the alarm doesn’t actually test the detector, it only tests that the battery is good.  In order to test the actual functionality of the alarm safely, you need a product like “Smoke Test“.  DO NOT USE A FIRE TO TEST YOUR ALARM.  Don’t be an idiot, think of how stupid you’ll feel if you burn your house down trying to test your alarm.

What if I can’t afford a

 smoke alarm?

In the city of Seattle and many other cities, the Fire Department will provide you with a smoke detector if you are unable to afford one.  Please contact your local fire department for more information.

What about Carbon Monoxide (CO)?

Carbon Monoxide is an odorless, colorless, tasteless gas that is toxic.  Because it’s impossible to detect by us mortals, it’s often called the “silent killer”.  According to the CDC, “For the period 1999–2004, an average of 439 persons died annually from unintentional, non–fire-related CO poisoning (range: 400 in 1999 to 473 in 2003)”.  
Carbon monoxide is a by product of combustion and CO poisoning is often a result of a poorly running or poorly ventilated furnace or other fire inside the house.  Because we can’t detect it naturally, a CO alarm is a must for any home that has gas or oil powered appliances.  I think every home should have one on each floor, regardless of heat source.
CO alarms are also relatively inexpensive, in the $20 range.

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