About our test

Smoke alarms test

Back in May 2006 we tested how well photoelectric and ionisation alarms reacted to smoke from a flaming wood fire or a smouldering fire.
 
We found then that photoelectric smoke alarms gave you significantly more protection than the more common ionisation models – particularly for smoke from smouldering fires.  
 
The toxic smoke from smouldering fires can kill. These types of fires are surprisingly common, too – usually when furniture, bedding or electrical appliances catch fire. Good photoelectric alarms detect low levels of this smoke and give you time to escape.

In 2006 we reported on an incident where a house filled with smoke yet three ionisation alarms failed to go off. Fortunately, a child coughing from the smoke woke the householder and a tragedy was averted.

What we found

This new test reinforces those findings. This time we tested 1 dual model (photoelectric and ionisation), 7 photoelectric and 10 ionisation models – 18 in total.

We tested them against a flaming wood fire and a smouldering fire at different levels of smokiness. And because smoke alarms are installed in hard-to-reach places, we assessed the difficulty of operating the test buttons with the end of a sharp and a blunt broomstick. We also noted how long it took for the alarm to activate after pressing the test button.

The dual sensor and the photoelectric models gave the best protection from both types of fire. The ionisation models were slightly better on average at detecting flaming fires, but were hopeless for smouldering fires. Many of them didn't sound at all during the smouldering fire test-runs. That failing is potentially fatal. 

If your house has ionisation alarms you need to supplement or replace them with our “recommended” or “worth considering” photoelectric models.

How we tested

Our test was conducted in the fire laboratory of the Building Research Association (BRANZ). We bought 3 examples of each model. Our results are the average of the performances of the three examples.
 
The alarms were fixed to a ceiling panel in a mocked-up hallway adjacent to the door opening of a fireproof room (which was about the size of a single-car garage).

• The flaming fire test
  A grid of nine 50mm-square 300mm-long sticks was constructed in the fireproof room and set alight using a small quantity of methylated spirits. The resulting smoke built up in the room and billowed into the mock hallway.
• The smouldering fire test
  A 60W electric soldering iron was pre-heated and laid horizontally on to a 300mm-square piece of 75mm-thick polyurethane upholstery foam. An electric fan was used to ensure the resulting smoke was evenly distributed. The resulting smoke built up in the room and billowed into the mock hallway.

In both tests, the smoke density was measured at the location of the alarms using a laser light-source and detector.