Multi-sensor safety

Andy Speake of Aico discusses how multi-sensor alarm technology is reducing costs as well as increasing safety from false alarms in social housing

Aico introduced the first mains powered domestic multi-sensor to the smoke alarm market in 2014 as a means of reducing false alarms and providing the best response to all fire types, making alarm specification and installation simpler in the process. Since then, ranges of multi-sensors have entered the domestic market and have been growing rapidly in popularity, notably in the social housing sector.

The typical multi-sensor uses both optical and heat sensors within the same alarm unit, although other variations exist. Multi-sensors vary dramatically in design, from basic models where there is limited cross evaluation of the sensor values, through to highly sophisticated devices that can assess the variation in values from each sensor in order to determine the nature of the potential fire. Consequently, their ability to detect fires while discerning false alarm sources is a very mixed bag indeed.

However, the more sophisticated devices are extremely effective at providing a quick response to both slow smouldering and fast flaming fires, while remaining more impervious to kitchen fumes and contamination, which are so often the cause of false alarms. The Building Research Establishment (BRE) 2018 Briefing Paper – ‘The performance of multi-sensors in fire and false alarm tests’ – reports on the findings of its testing of 35 different optical heat multi-sensors. It estimates that potentially 38.1 per cent of observed false alarms could have been reduced if multi-sensors had been present.

Cost implications

Multi-sensors are more sophisticated than single sensor alarms and are priced accordingly; however you are getting two alarm types in one and, with the more sophisticated models such as our own, there are complex algorithms interpreting the signals to get a better understanding of what is really happening in the immediate environment. Depending on the model, you will probably be paying around 15 per cent more per unit for a multi-sensor. So why are so many people, especially those in the social housing sector, specifying multi-sensors?

With multi-sensors, you are getting the best of both worlds: improved protection and reduced costs when you take into account the financial implications of reduced false alarms that multi-sensors bring. Using our market knowledge, along with insights from a range of Registered Social Landlords across the UK, we have run some figures, and they make for interesting reading. Based on 10,000 properties where smoke alarms are fitted to the minimum category of protection, LD3, we estimate a potential saving of £101.5k on call out costs when compared to fitting an optical alarm.

That saving more than doubles when alarms are fitted to the medium protection category LD2, which is increasingly being adopted following recent changes to BS 5839-6:2019 (the code of practice for the design, installation, commissioning and maintenance of fire detection and fire alarm systems in domestic premises) and changes to Scottish legislation. We estimate that switching to quality multi-sensors can reduce call out rates by an incredible 90 per cent, resulting in a maintenance cost saving which offsets the initial higher purchase cost and still provides an overall saving. Social housing providers are very much in tune with this. South Cambridgeshire District Council are using mains powered multi-sensors, along with heat and carbon monoxide alarms, in its 1400 sheltered housing properties.

The smoke alarm systems are being installed to Category LD2, with a heat alarm in the kitchen, a multi-sensor in all circulation spaces and entrance halls and carbon monoxide alarms in properties that are not fully electric. “It is imperative to specify the right product for the right situation” states Eddie Spicer, M&E surveyor for South Cambridgeshire District Council. “Obviously, cost is a major factor and with the introduction of the latest technologies in the multi-sensor, the lack of false alarms has paid dividends with lower call out rates and nuisance alarm activations.” The multi-sensor may only have been in the domestic market for a mere five years, but what an impact it has made during that short time!

Social housing providers have been quick to realise the benefits in terms of improved tenant safety and a reduction in false alarms and overall costs. With increasing evidence of the benefits of multi-sensors and the move to LD2 smoke alarm systems which require a higher level of protection, involving more alarms per property, the rise of the multi-sensor looks set to continue.

Andy Speake is national technical manager of Aico