Difference Between Photoelectric and Ionisation Smoke Alarms
October 17, 2014

Photoelectric and Ionisation Smoke Alarms for Smoke Alarm Maintenance


With a 60 Minutes special investigation exploring the potential dangers of ionisation smoke alarms airing on Sunday 19th October 2014, we thought to provide some clarity around the state of play and explain the differences between the two key types of smoke alarms used in Australia.

 

Missed the feature? Watch this short clip from 60 Minutes ‘Extra Minutes’ and get the information you need to keep your property and your family safe.

 

 

Two types of smoke alarms are commonly found in Australian homes; Photoelectric and Ionisation. It is important to note that currently both types can be legally purchased and used as both meet the required Australian Standard AS3786. However, for a number of years now photoelectric smoke alarms have been the only type recommended by Australian Fire Authorities and Fire Brigades, as well as the International Association of Fire Fighters. In fact, a global campaign is now calling for a total ban of ionisation alarms. Within Australia, the Northern Territory is ahead of the curve with the Northern Territory Fire Service already legislating against the use of ionisation alarms in the region.

 

But what’s the difference and why are photoelectric detectors so highly recommended? For the most part, it’s all about how they detect fires and importantly, how quickly they respond.

 

Photoelectric Smoke Alarms

 

These alarms detect visible particles of combustion so it is often said that they ‘see’ smoke. They work by aiming a light source into a sensing chamber so that when smoke particles enter the chamber, light is reflected onto the sensor, triggering the alarm.

 

The fact is that in both the real world and controlled instance of smoke alarm testing, they have been proven to be more effective and respond significantly faster to smouldering fires. These are fires which are slower burning and produce a lot of smoke, the most common type in the home environment. The faster you can be alerted, the more precious time you have to get yourself and your family to safety. They are also less likely to emit false alarms from cooking or steam in the bathroom.

 

Ionisation Smoke Alarms

 

These alarms are said to ‘smell’ the smoke that comes from flames in that they detect invisible particles of combustion. As opposed to photoelectric alarms these work though a small amount of radioactive material that exists between two electrically charged plates. This material ionises the air causing a current between the plates. When smoke enters the chamber the flow is disrupted, activating the alarm.

 

While they are not generally recommended over photoelectric detectors, they do activate more quickly for fast flaming fires. The disadvantages however are significant. They are slower to respond to smouldering fires, which can lead to visibility and breathing difficulties when occupants are attempting to escape a house fire. They are also prone to more false alarms, resulting in people removing the battery and thereby losing all protection.

 

How can you tell what’s in your home?

 

It should be clearly stated on each smoke detectors label whether it is an ionisation or photoelectric smoke alarm. However, if it is not clearly stated you will see a bright yellow ‘radiation’ symbol inside or on the back of an ionisation alarm.

 

The Detector Inspector Service

 

In accordance with the recommendations of Australian Fire Authorities and in the interest of ensuring maximum occupancy safety, Detector Inspector technicians only install and replace smoke alarms with photoelectric smoke detectors as part of our annual smoke detector maintenance service. Now until November 30, 2014, we are offering our clients a heavily subsidised ‘change-over’ service to change their existing ionisation alarm for a photoelectric alarm for complete peace of mind. For more information, download our Position Statement.

 

If you have any questions in relation to smoke alarms, home fire safety or the change-over offer please don’t hesitate to contact us.