Smoke alarms

We tested 12 models to see which respond fastest to smoke.

Smoke alarm on ceiling.

A smoke alarm has one job – to alert you to fire so you can get out of your home safely.

We tested photoelectric and ionisation alarms to see which respond fastest to smouldering and flaming fires, and found not all smoke alarms are created equal.

Choose photoelectric

We recommend you choose photoelectric alarms. Fire and Emergency New Zealand also recommends photoelectric alarms, and the Residential Tenancy Act requires landlords to replace expired smoke alarms with long-life battery photoelectric smoke alarms. 

Smoke from a flaming waste paper bin or cooking oil fire is different from that produced by the cooler smouldering of upholstery foam, bedding or the plastic bits of electrical equipment. However, both types of fire are deadly.

Our test found that photoelectric alarms were good at detecting both flaming and smouldering fires.

Replace ionisation alarms

Our Product test manager Paul Smith sat down with RNZ's Simon Morton to discuss our findings on smoke alarms.

Radiation symbol.

Since we reported that the ionisation smoke alarms we tested were much slower at responding to smouldering fires, ionisation models have been removed from sale in New Zealand. We’ve also removed these alarms from our results.

If your home still has ionisation alarms, supplement (or replace) them with our recommended photoelectric models.

Ionisation alarms require a tiny amount of radioactive material to make them work. You can identify one by the radiation symbol somewhere on the plastic body.

Choose long-life lithium batteries

The majority of smoke alarms now come with a built-in, sealed, long-life lithium battery, good for 10 years’ use.

Alarms with 9-volt batteries could save you money up front (you’ll find models for about $10). That might be tempting, but we advise against it. A 9-volt battery will last for about a year before it’ll need replacing.

A smoke alarm with a battery running down results in annoying “2am chirps”. These always occur in the middle of the night when it’s colder. The chirps are another reason why smoke alarms get taken down, or batteries get removed and not replaced.

We’ve had reports from members of some long-life sealed models failing sooner than expected. We recommend keeping receipts (it’s a good idea to take a photo) and note when your alarms were installed. If they don’t last the advertised 10 years, take them back to where you bought them and demand a refund or replacement.

Hard-wired alarms

Some smoke alarms can be hard-wired into your home. This is a great idea, but installation is more involved (and costly) than for battery models as you need to run wiring to each location. You’ll need the services of an electrician. Make sure a wired-in alarm has a backup battery installed so it’ll work in a power cut.

Where to fit your smoke alarms

At a minimum, you should fit an alarm in every bedroom and hallway.

Smoke alarms room plan.

The New Zealand Building Code requires an approved smoke alarm to be fitted in every escape route (hallway) and within 3m of every sleeping space (bedroom) door. Fire and Emergency New Zealand goes further and recommends installing a smoke alarm in every bedroom, hallway and living area, on every level in the house.

Alarms must be installed on or near the ceiling (because smoke rises). There’s evidence an upstairs alarm in a stairwell is likely to respond before one fitted downstairs, even when the fire is downstairs.

Building code and rental rules

The Building Code requires all residential buildings to have smoke alarms.

Smoke alarms must have a hush button – to allow nuisance alarms to be cleared without removing the battery – and a test button. They must comply with at least one of the following standards:

  • UL 217
  • CAN/ULC S531
  • AS 3786
  • BS 5446:Part 1

Rental requirements

The Residential Tenancies Act states every rental property must have working smoke alarms fitted at the start of a tenancy. New smoke alarms must be:

  • photoelectric models with a battery life of at least eight years (or be hardwired) and fitted according to manufacturer’s instructions
  • installed within 3m of each bedroom door, or in every room where a person sleeps
  • in each level or storey of a multi-storey or multi-level home
  • in all rental homes, boarding houses, rental caravans, and self-contained sleep-outs (holiday lets are exempt).

False alarms

Nuisance alarms aren’t just a response to burning toast. They can also be caused by high humidity, dust and insects. Every alarm has a “hush” button, but it will sound again seconds later unless the source is removed.

Frustration from false alarms results in batteries being removed, or alarms removed entirely. However, if a real fire strikes, you’ll be at risk.

You can minimise false alarms by:

  • Carefully positioning your alarms – don’t put one within 3m of the kitchen or bathroom.
  • Avoiding putting alarms close to heat pumps or heating vents that stir up dust.
  • Using a rangehood or extractor when cooking or showering and try to keep doors closed.
  • Taking your alarms down occasionally and vacuuming them to remove dust and dead bugs.

Brand reliability

Reliability of models up to five years old. Data from our 2019 reliability survey with 902 responses.

Smoke alarms for the hearing-impaired

Fire and Emergency New Zealand says the ideal alarm for the deaf and hearing-impaired is a hard-wired series of interconnected photoelectric smoke alarms fitted with bed-shakers, strobe lights, or pagers.

These systems can be expensive, but if you meet certain criteria you may qualify for funding for a system to be installed by the Ministry of Health or Housing New Zealand. Contact Deaf Aotearoa to learn more.

Why is this free?

This report is free thanks to funding from Tenancy Services.

Consumer NZ is non-profit. To help us get a fairer deal for all New Zealand consumers you can become a Consumer member or make a donation. We’ll use your contribution to investigate consumer issues and work for positive change.


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