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BRE and Scottish Government collaborate on optical smoke detectors and alarms-focused research study

11 May 2021

THE BUILDING Research Establishment (BRE) has collaborated with the Scottish Government, the Scottish Fire and Rescue Service, the Fire Industry Association (FIA) and FIA member company Detectortesters to conduct a joint research study supported by the BRE Trust. The research group has worked together to determine the optimum replacement periods for optical smoke alarms (as used in domestic dwellings) and for optical smoke detectors deployed in commercial premises.

Ten different models of each detector type were tested and suitable performance limits established using specialist smoke sensitivity measurement equipment (ie Detectortesters’ Trutest system). The same portable test equipment was then used to evaluate 107 commercial smoke detectors and 85 domestic smoke alarms in the field during the period spanning February 2019 through until January last year.

When tested in service environments, it was observed that the sensitivities of smoke detectors and smoke alarms were relatively consistent independent of age. However, older domestic smoke alarms demonstrated a slight increase in their sensitivity, in turn leading to an earlier alarm response. It was also observed that the sensitivity of both optical smoke alarms and optical smoke detectors increased as they became dirtier.

In the UK, there’s no strict mandatory period of replacement within British Standards BS 5839-1 for commercial smoke detectors and BS 5839-6 for domestic smoke alarms. While some countries such as Germany and Spain do have them, there appears to be no independent evidence to support the replacement periods.

For many years, optical smoke detectors have been preferred and dominantly used in the commercial sector. In times hence, the use of optical smoke alarms and detectors is expected to be dominant in the built environment, so this latest research work focused on optical devices only. Ionisation-centric devices were excluded from this study.

Sensitivity responses analysed

By analysing the sensitivity responses in tandem with the age of the devices under examination, the research group has recommended replacement periods for commercial smoke detectors, with and without drift compensation, as well as for domestic smoke alarms. Further recommendations have also been made to improve practices around the use of these life safety devices.

The detectors tested in the field were aged between 0 and 30 years whereas the alarms were aged between 0 and 12 years. The stakeholder group reviewed the data that was gathered. Based on that data, the following replacement periods have been proposed:

*All smoke alarms should be replaced no later than 12 years after their date of manufacture

*The maximum replacement period proposed for commercial smoke detectors without drift compensation should be 25 years

*The maximum replacement period proposed for commercial smoke detectors with drift compensation should be 30 years

Four further recommendations have also been made. These are to:

*test more old smoke alarms and detectors in the future

*label the installation date on smoke alarms and detectors

*perform a similar study with heat alarms tested in situ

*periodically measure smoke detector sensitivity to track changes in performance with time

Heat alarms-focused study

BRE Global is now exploring a similar collaborative study involving heat alarms (present in domestic kitchens) in a bid to investigate whether these devices – when contaminated with dust and oil – could result in a delayed response during a fire scenario.

*Full copies of the report entitled ‘Determining the Optimum Replacement Periods of Optical Smoke Detectors and Alarms’, which is authored by Raman Chagger (principal consultant on fire safety at the BRE) and Gemma Forbes-Pepitone (fire consultant at the BRE), are available to view online. The BRE has kindly requested that individuals do not download and circulate this Briefing Paper, but instead inform their colleagues and others of the URL. Doing so will greatly assist the BRE in gauging the level of interest in its publications, while also enabling readers to provide feedback