New Zealand homes commonly have two types of smoke alarms: photoelectric and ionisation. In this article, we will be explaining some common differences between these two types of smoke detection systems.
Ionisation smoke alarms
Ionization smoke alarms were initially developed for industrial and commercial settings in the mid-20th century. They were designed to detect the presence of smoke particles by measuring changes in the electrical current between two plates within the alarm.
For many years, ionisation smoke alarms were the most common type found in homes due to their widespread availability and lower price point.
Photoelectric smoke alarms
The concept of using light to detect smoke has roots in early fire detection systems. However, the modern photoelectric smoke alarm, as we know it today, was invented in the 70s.
Photoelectric alarms utilise the photoelectric effect, where light striking a material causes the emission of electrons.
The table below provides the comparison between ionisation smoke alarms and photoelectric smoke alarms:
| Feature | Ionisation Smoke Alarms | Photoelectric Smoke Alarms |
|---|
| Detection Method | Uses a radioactive source to detect changes in ionized air caused by smoke. | Uses a light sensor to detect smoke particles disrupting a light beam. |
| Best For | Fast-flaming fires (e.g., paper or grease fires). | Slow-smoldering fires (e.g., fires from furniture or bedding). |
| Response Time | Faster for fires with visible flames. | Faster for fires with thick, visible smoke. |
| Nuisance Alarms | More prone to false alarms from cooking or steam. | Less likely to trigger false alarms in these situations. |
| Cost | Generally lower cost. | Slightly more expensive. |
| Durability | Similar lifespan (~10 years) for most models. | Similar lifespan (~10 years) for most models. |
| Recommended Location | Kitchens, garages, or areas with risk of fast-flaming fires. | Bedrooms, living rooms, and hallways for better overall safety. |
| Compliance Standards | Less commonly recommended due to outdated technology. | Preferred in many jurisdictions for residential safety. |
Fire and Emergency New Zealand recommend long-life photoelectric smoke alarms. They are far more effective than ionisation alarms at detecting slow smouldering fires, which burn for hours before bursting into flames.
We have been suppling smoke alarms to our customers for over two years and we would recommend choosing a set of interconnect photoelectric smoke alarms that could link together wirelessly or through a hardwired connection.
Proper installation and placement of smoke alarms is very important for effective fire detection and we recommend certain locations as follows;
Bedrooms: Place a smoke alarm inside each bedroom to ensure early detection, especially when occupants are asleep.
Hallways Outside Bedrooms: Install an alarm in the hallway or corridor leading to the bedrooms to catch smoke from adjacent areas.
Living Room or Lounge: Mount an alarm in the living area where fires from electrical devices or fireplaces might occur.
Kitchen(near, but not too close): Place a smoke alarm at least 3 meters (10 feet) from cooking appliances to reduce false alarms.
Additional locations:
Stairways: For multi-story homes, place alarms on each level near stairways to detect fires spreading between floors.
Basements and Attics: If these areas are used, install alarms there as well.
Garage: Fires often start in garages due to flammable materials or vehicle malfunctions.
