Ionization smoke detector fails 'aquarium' test

We placed a soldering iron inside a piece of foam, along with an ionization smoke detector.
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Bob Segall/13 Investigates

Indianapolis - Will the smoke detectors in your home actually detect smoke? Before you answer, read what 13 Investigates has discovered. Our demonstration stunned the state fire marshal and provides more proof that the type of smoke alarm you choose does make a difference.

Over the past couple of months we've been reporting why it's so important to have a photoelectric smoke detector in your home. To make that point even clearer, 13 Investigates conducted a dramatic test to show the limitations of an ionization smoke detector.

It's called an aquarium test.

We placed some polyurethane foam from a couch cushion inside a glass fish aquarium, along with an ionization smoke detector (the kind of smoke alarm now in approximately 90% of U.S. homes). The smoke detector was brand new - straight out of the box - and it was tested just before the demonstration to make sure it had a working battery.

We then placed a soldering iron on the foam to create a slow, smoky fire inside the aquarium. Within seconds, smoke began to rise from the foam and, at that point, 13 Investigates placed a lid on the aquarium to seal in the toxic smoke.

Five minutes into the test, the aquarium appeared to be full of smoke. Still, the ionization smoke alarm did not sound.  

Eight minutes into the test, the aquarium was so full of smoke that the smoke detector inside was barely visible. The smoke alarm was completely surrounded by smoke and yet it still was not sounding.

Moments later, a carbon monoxide detector inside the aquarium activated, alerting us to the dangerous conditions inside the fish tank. Still, the ionization detector was silent.

Eleven minutes into the test, the carbon monoxide level reached 215 parts per million. That's enough to make you feel sick and well above the reading at which firefighters are required to put on protective breathing equipment. Inside the aquarium, the smoldering fire was about to make those levels go much higher.

At seventeen minutes, it was over 400 parts per million. Twenty-three minutes into the test, the reading jumped up to 872 parts per million. That much carbon monoxide gas can bring on dizziness and convulsions and, over time, that level of exposure could kill you.

Twenty-five minutes into the test, still nothing from the ionization smoke alarm. But the carbon monoxide detector had reached 999 parts per million - that's as high as the CO detector would go. At that point, we opened the lid slightly to put a photoelectric smoke alarm inside the smoke-filled aquarium. It went off in less than five seconds.

After 30 minutes, it seemed clear the ionization alarm was not going to sound so we decided to end the test. We took the aquarium into the WTHR parking lot to remove the lid in a well-ventilated location and to get rid of all that toxic smoke. We could still hear the photoelectric smoke alarm sounding, but what about that brand new ionization smoke detector that did not work while it was surrounded by smoke? Once all the smoke was gone, we pressed the test button on the smoke alarm one more time to make sure the battery inside the alarm was still working. It beeped, proving that it still had a working battery.

Bottom line: the ionization smoke alarm did not activate while surrounded by thick smoke and very dangerous levels of toxic carbon monoxide gas.

But the test was not done just yet.

13 Investigates took that same smoke alarm and installed it a kitchen. (Experts do not recommend doing that for reasons we are about to explain.) We then put a few pieces of bread into a toaster and within two minutes - before our toast was ready - the ionization smoke alarm blared loudly.  That's right, our smoke alarm sounded from simply making toast.

You might have a smoke detector that does the same thing.

Why will it sound quickly while you're cooking or making toast, and not activate when it's surrounded by deadly levels of smoke? Here's the answer:

Ionization smoke detectors respond to tiny particles -- the kind of small particles that come from a very hot, fast-burning, flaming fire -- or, in this case, from cooking food.

But a slow, smoldering, smoky fire does not produce tiny particles. It creates very large particles. Photoelectric smoke alarms are able to recognize those big smoke particles, but ionization smoke alarms often cannot.

That's why experts recommend photoelectric smoke alarms -- not ionization ones -- close to kitchens. Putting an ionization alarm in or close to your kitchen increases the odds of nuisance alarms. If you have this problem, do not take the batteries out of your smoke detector! Consider replacing it with a photoelectric smoke detector.

WTHR conducted the aquarium test after talking with Adrian Butler, co-founder of the World Fire Safety Foundation in Australia. Butler conducted the first aquarium test demonstration and has been trying to educate the public about the importance of photoelectric smoke detectors ever since.

"It's a real eye opener," Butler said. "It really shows the problem with ionization smoke alarms in a way that everyone can understand."

What kind of smoke detector do you have?

Photoelectric smoke detectors usually have the word PHOTOELECTRIC right on them. You might see a big "P" or a "blue symbol". And if you see the words "dual sensor," that means the smoke detector has both photoelectric and ionization built in. 

If you don't see any symbols chances are, it's probably an ionization smoke detector.  Those alarms are sometimes marked with a letter I, or other symbols

When you are taking a look at your smoke detector, please make sure to check the battery. That's crucial.

And remember, smoke detectors do save lives. Adding a photoelectric smoke detector to your home will usually give you more warning in a slow-burning, nighttime fire.

WTHR has teamed up with HH Gregg to help you get a combination smoke alarm. That will detect smoke from a flaming fire OR a slow smoky one like the one you just saw. You can get yours at a big discount at all area HH Gregg stores.

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