The Lifespan of a Smoke Detector

The smoke detector is arguably the most important mitigator in fire risk assessment. They are, of course, crucial for giving occupants early warning indication of a fire and are used to mitigate extended travel distances and risks associated with inner rooms. They can also be used in more complex installations to operate smoke ventilation systems, shut fire doors and a myriad of more life safety-critical functions. It is no surprise that it is vital that the smoke detector sounds quickly to alert occupants before a fire is a blazing inferno.

What might surprise you is that smoke detectors have a shelf life due to environmental factors and general deterioration of the component parts.

It is interesting then, as we know smoke detectors deteriorate over time, that there is nothing in place within the current industry standards which gives a replacement schedule. The only existing guidelines are manufacturer recommendations which are often interpreted as a money-making swindle.

Back in the early noughties, I worked for a large national fire and security business which initiated an annual maintenance and replacement program for devices over 10 years old. The detectors were removed and sent away for refurbishment and replaced with refurbished models.

In 2015 one of the company’s customers had a fire in a storeroom at their multi-story office block. When the smoke got onto the escape route and reached the smoke detector nothing happened. Fortunately, a security guard spotted the smoke on a CCTV and raised the alarm. During the investigation, the CCTV showed that the engineer had tested the device the week before and the smoke detector sounded as expected. On closer inspection, we saw that the smoke spray was “injected” into the chamber whereas, in the real-life fire, the smoke did not behave like that and flowed in naturally.

In 2016 whilst carrying out some tests on smoke detectors for my dissertation, which focused on the delay of activation due to high airflow in server rooms, I took the opportunity to test some old smoke detectors which had been removed as working units during a refurb.

The results were staggering.

The test rig, pictured, is 500mm x 500mm with an inlet for a fan and an outlet with a smoke detector installed. Some PMMA (a ‘dirty’ burning material that produces a lot of smoke) was ignited on a tray and inserted into the test box. The new detector operated within 7 seconds. However, when we carried this out with 3 of the older detectors these took up to 1 minute 27 seconds to operate.


Now, this was hardly a BRE scientific full-scale test, but the results are still worth contemplating. It highlights the issue of the deterioration of smoke detectors and raises the question as to whether the industry needs to deal with this. Clients see manufacturer recommendations as exactly that, a recommendation and one that very few follow.

As an industry, we need to come together and make a decision on what is an acceptable life span for an optical smoke detector and get a replacement matrix into BS5839.

For more information about our Fire Safety and advice about keeping your workplace safe, contact Matt Spivey at Synergy Fire Engineering on (0)843 658 1310 or email [email protected].

Matt Spivey is Managing Director of Synergy Fire Engineering, the only BAFE SP205 accredited Fire Risk Assessors in Derbyshire. A member of the Institution of Fire Engineers, Matt is highly qualified and holds a BEng (Hons) in Fire Engineering.  For more information about our fire safety training call Synergy Fire Engineering on 01629 828 881 or email [email protected]