Which type do you need?

Smoke from flaming wood or cooking-oil fires is different from that produced by the less-hot smouldering of upholstery foam, bedding or the plastic components in electrical equipment.

• Ionisation alarms sense the volatile combustion products from hot flaming fires, but don’t do as good a job sensing the smoke from cooler smouldering fires because fewer combustion products are present.
• Photoelectric alarms shine a light beam across a chamber and detect if the air in the chamber becomes partially obscured. So they can detect smoke from both types of fires.

Do you need both types?

The deluxe solution is to have both photoelectric and ionisation alarms. The First Alert SA302CN dual-sensor alarm in our test gave the best overall protection against both types of fires, but it was by far the most expensive model.

All our other “recommended” and “worth considering” models are photoelectric. Some of these cost much the same as ionisation models – and they give much better overall protection.

Radiation symbol

Having several dual sensor or photoelectric models in appropriate locations in your home should give you good protection. See Building code requirements for information on where to fit the alarms. 

How can you tell what type you've got?

Ionisation models require a tiny amount of radioactive material to make them work. So all of them will have the radiation symbol somewhere on the plastic body.

Smoke alarms for the hearing-impaired

The Hearing Association Wellington imports alarms designed exclusively for deaf and hearing impaired people. The main base unit is placed by the bed and a vibrating pad is placed under the pillow.

More information can be found on the Association website: http://www.hearwell.co.nz.