Life Spans of Photoelectric and Ionization Detectors and the Importance of Replacing Them

Posted on: July 16, 2017

Learn when to swap out old smoke detectors, and which types are better at what

Smoke detectors are a given in most structures, but are they being properly maintained? While most homes and business have fire safety alarms, some individuals don’t fully understand how these units work, which to purchase, and the necessity of testing and replacing them on a regular basis.

In fact, some owners or managers of commercial facilities assume that if detectors are properly installed and working, little maintenance or replacement is required. These devices wear out, however. And they have a chance of failure at roughly five or ten-year intervals, depending on the type.

Two main types of smoke detectors

There are two types of detectors that are commercially available, offering protection from fire and smoke in different ways. Home consumers often purchase the cheapest unit when looking for a new smoke detector, without fully researching its capabilities. And while commercial buyers are more likely to use a combination of both varieties, they should avoid adopting a ‘set it and forget’ way of thinking about these vital fire safety tools. Here are the details on each:

Ionization smoke detectors

An ionization smoke detector is typically cheaper to make and is popular among individuals looking for a budget-friendly option. It uses a small, essentially harmless radioactive element (0.9 microcurie of americium-241, to be precise) that creates an electrical current between two plates in an ionization chamber. When particles of smoke enter the chamber, the detector senses the break in current and sets off an alarm. These units are very sensitive and therefore prone to false alarms. They are also quicker to detect flaming fires but less adept at sensing smoldering fires.

Photoelectric smoke detectors

Photoelectric detectors use both a sensor and a light source to detect smoke. When smoke travels between the two, some of the light is refracted 90 degrees off the smoke particles and hits the sensor, tripping the alarm. A downside to these types of units is that the photo lens can become dirty, making the detector less accurate. They are also typically more expensive than ionization smoke detectors because of their more complicated components. Photoelectric detectors excel at sensing smoky, smoldering fires and trigger fewer false alarms.

NPFA recommends using both – and replacing them at least every 10 years

The National Fire Protection Association (NFPA) recommends that both types of alarms (or dual sensor smoke alarms) are used, and stipulates that individuals should test detectors at least once per month and maintain them per the manufacturer’s instructions, including checking the power source and properly cleaning any sensors.

And since detectors can become less effective over time, they need to replaced at least every 10 years. There is a caveat to this guideline, however: some fire safety experts recommend a shorter shelf-life for photoelectric units and advocate installing new ones about every five years.

State building codes are beginning to change

In an effort to further protect individuals from all types of fires, state building codes are starting to adapt. In the state of Massachusetts, for example, new homes can’t simply rely on ionization alarms; a detector must be photoelectric if it is placed within 20 feet of a bathroom or kitchen. Similarly, Vermont has passed legislation requiring all homes that are built or sold to have at least one photoelectric smoke detector on each floor.

Be safe: consider both and make sure you replace them

Regardless of the level of protection your home or business has from ionization detectors, photoelectric, or some combination of the technologies, it is essential to replace the units at least every ten years, if not before, and test them regularly. For more information about smoke detector technology and maintenance, or any other aspect of your home or business’s life safety systems, reach out to the safety experts at LifeSafety Management at (800) 330-1158 or through our contact form.