Smoke detectors are devices that are able to detect smoke in the event of a fire and sound an alarm to alert people to the potential danger.
Two main types of smoke detectors are available for household use: photoelectric and ionisation smoke detectors. Both are effective and able to meet Australian Standard AS 3786-1993: Smoke Alarms, but they work in different ways to detect smoke.
Photoelectric smoke detectors are activated by large particles in smoke and are good at detecting fires that smoulder.
Ionisation smoke detectors contain a very small amount of radioactive material and detect the charged particles that come off flaming fires.
Choosing a smoke detector
Fire & Rescue NSW provides the following advice on these detectors:
‘Photoelectric alarms appear to provide a faster warning than ionisation alarms in most circumstances, and there is little appreciable difference in performance during flaming fires.
‘To maximise the opportunity for early warning in all fire scenarios, the FRNSW recommends the installation of photoelectric alarms, hard wired and interconnected, in all residential accommodation. If only installing one alarm, it should be a photoelectric alarm.’
For more information on smoke detectors and fire safety, visit Fire & Rescue NSW.
Ionisation detectors contain a very small amount of radioactive material called Americium-241 which is bound in a metal foil. Americium-241 emits alpha particles and low energy gamma rays. The alpha particles are absorbed within the detector, while most of the gamma rays escape harmlessly.
For this reason, the radiation dose from detector to householder is very low and can be less than natural background radiation. The benefit of having the smoke detector vastly outweighs any health risk from the radiation.
If unsure about the type of detector you have, check the base for a radiation symbol and description of the type of radiation, Americium-241. If these are located on the detector, it contains radioactive material.
Americium-241 has a half life of 432 years. This is the time taken for it to decay to half its original activity. Even though the radiation emitted during this process is very small, it will persist in the environment for hundreds of years, so it is important to consider the environmental impact when choosing a smoke detector.
The ARPANSA website has more information on ionisation smoke detectors.
Disposing of smoke detectors
Photoelectric detectors can be disposed of in any quantity in the normal waste stream. Alternatively smoke detectors can be taken to a community recycling centre.
As the level of radiation is very small and does not present a health hazard, the EPA advises that small numbers of ionisation smoke detectors can be safely disposed of in general household rubbish or taken to a community recycling centre.
However there may be regulatory requirements for disposal of 10 or more ionisation detectors at the one time. In these cases, you should contact the EPA for further advice on disposing of bulk items as follows:
Hazardous Materials, Chemicals and Radiation Section
NSW Environment Protection Authority
PO Box A290, Sydney South NSW 1232
Phone: 131 555 (Environment Line)
Facsimile: (02) 9995 6603