Smoke and smoke alarm

Retailers should stop selling ionisation smoke alarms

A Consumer NZ test of smoke alarms found ionisation-type smoke alarms performed so poorly retailers should pull them from the shelves.

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Ionisation alarms give much less warning of smouldering fires, such as those caused by faulty electrical wiring, curtains draped over a heater, or a hot ember igniting upholstery foam, making it less likely you can get out of your home safely.

Consumer NZ head of testing Dr Paul Smith recommends people buy photoelectric alarms. Fire and Emergency New Zealand also recommends photoelectric alarms. The Residential Tenancies Act requires all new alarms landlords install to be photoelectric with a long-life battery.

An ionisation alarm can be identified by a radiation symbol somewhere on the alarm body.
An ionisation alarm can be identified by a radiation symbol somewhere on the alarm body.

However, despite a wide range of photoelectric models on offer, ionisation models are still available to buy. “We think ionisation alarms should not be sold and are working with retailers to remove them from their shelves,” Dr Smith says.

All smoke alarms will respond to a fire, eventually. “The difference is whether they respond to visible smoke. A smouldering fire can fill a home with deadly smoke long before it bursts into flames.”

Consumer NZ testing confirmed ionisation models were great at detecting flames, but not so good with visible smoke. “The four ionisation alarms in our test were faster at detecting flaming fires (burning oil and wood) but much slower at detecting smoke from smouldering foam,” Dr Smith says.

People should check which type of smoke alarm they have in their homes and rental properties. “You can identify an ionisation alarm from a radioactive symbol somewhere on the alarm body – it may be underneath, so you might need to remove it to check.”

Consumer NZ advises people:

  • Not to remove working ionisation alarms – any alarm is better than no alarm.
  • If only ionisation alarms are fitted, you should also fit photoelectric models at least in hallways and escape routes.

For rental properties:

  • Landlords have to ensure working smoke alarms are installed at the start of a tenancy. Existing ionisation alarms can stay where they are, but all new smoke alarms must be photoelectric models with a long-life battery.
  • Tenants must not remove smoke alarms, and are responsible for replacing dead batteries.

To see which photoelectric models performed well, see our test results.

About Consumer NZ’s test

Our test, based on the UL217 standard for smoke alarms, was conducted at an independent lab. Multiple alarms were placed in our “smoke-sensitivity chamber”. Smoke was introduced from flaming wood, flaming oil, smouldering wood chips, and smouldering upholstery foam. We tested three samples of each alarm model and assessed their response to smoke compared to three control sensors.

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