Causes of false fire alarms in buildings

This project investigated why false alarms occur in buildings and identified approaches that could reduce their occurrence. Kings College London (KCL) and Buckinghamshire & Milton Keynes Fire Authority (BMKFA) contributed basic data for analysis by BRE.

A review of data from false alarm incidents provided by KCL, revealed that replacing existing detectors with intelligent multi-sensor detectors (that detect more than one fire phenomena) was the action that could potentially reduce false alarms by the greatest amount (69%).

Impact

The knowledge gained from this and the follow-up false alarms study has enabled BRE to offer a consultancy service to help organisations reduce false alarms.

Research outputs and impacts

To date the team has produced six briefing papers and three summary videos – all available free of charge from the Fire Safety Research website. The projects are followed up to ensure that they are promoted and the findings are implemented. Impacts of this work have included:

  • being used to revise existing codes of practice, e.g. BS 5839-1 for commercial fire detection systems, or develop new ones, e.g. LPCB CoP 0001 for visual alarm devices,
  • supporting the development of product test standards, e.g. BS EN 54-23 for fire detection and alarm systems,
  • being adopted and integrated into processes used by fire and rescue services,
  • leading to more research that has generated further knowledge,
  • Fire Industry Association-produced guidance documents on specific products for industry,
  • supporting the FIA to produce qualifications for fire detection and alarm engineers,
  • providing guidance for building owners, managers and responsible persons,
  • informing product manufacturers on how to improve their products.

Characterising smoke from modern materials and evaluating smoke detectors

The materials used in modern homes have changed significantly in recent decades. This research investigated whether smoke detectors could respond to the smoke produced from new materials during a fire. Currently the four test fires used in standards to assess smoke detectors were developed in the 1980s and represent a broad range of smoke types expected in commercial and domestic environments at the time. The smoke characteristics for a range of new materials were measured and compared with the existing four test fires. The performance of approved ionisation and optical smoke detectors to the smoke produced from these alternative materials was also assessed.

It was confirmed that both ionisation and optical smoke detectors are attuned to detecting certain types of fires and that existing standards remain suitable for assessing these technologies.

Impact

The knowledge gained from this study enabled more challenging test fires to be developed that were used during the multi-sensor research work. These are expected to contribute towards the Loss Prevention Standard (LPS) for false alarm resistance and will demonstrate the ability of more advanced detectors to respond to more challenging fires.

Visual alarm devices – their effectiveness in warning of fire

Visual alarm devices (VADs) provide visual warning of fire for deaf and hard of hearing people, as well as in areas of high ambient noise (e.g. factories) or where a silent alarm is preferred (e.g. operating theatres). There is much to be learnt about what type of visual signal provides the most effective warning for people.This project investigated the pulse duration of VADs by comparing the responses of a group of participants to flashing Xenon and LED devices of varying pulse durations.

Analysis of this data revealed that as the pulse durations of LED devices shorten the attention drawing effectiveness increases. It also demonstrated no significant difference in responses between warm white LED devices and cool white LED devices. The Xenon and 10ms cool white LED device had similar responses.

Impact

This work has led to changes in US and British codes of practice and has influenced manufacturers of VADs to produce devices with shorter pulse durations. Further research work, funded by 13 VAD manufacturers, is currently in progress to identity other factors that influence the effectiveness of visual fire warning for people.

Live investigations of false fire alarms

Conceived as a result of the work on the false fire alarms, this project aimed to identify the fundamental causes of false fire alarms, using an industry expert to investigate false alarms as they occurred in the field in the greater Glasgow area.
The investigator joined Scottish Fire and Rescue Service crews on live callouts and, following a comprehensive investigation, completed online reports for each false alarm – this form of ‘live’ false alarm investigation had not previously been conducted.

Following analysis of the data gathered, recommendations were made across nine different stakeholder groups ensuring that fire and rescue services, fire risk assessors, business owners, fire alarm contractors as well as trade associations and others all play their part in collectively reducing false alarms in the UK.

The performance of multi-sensors in fire and false alarm tests

The reliable early detection of fire with minimal false alarms over a broad range of applications is a challenge. The detection of smoke-like phenomena commonly found in the service environment, such as cooking fumes, steam, aerosols and airborne dust, contribute to false alarms. Multi-sensor detectors use a combination of more than one type of sensor – smoke, heat or carbon monoxide – to detect the presence of a fire. A research group, comprising the Fire Industry Association, BRE and fire detector manufacturers, investigated the immunity of multi-sensor detectors containing smoke and heat sensors to common causes of false alarms, as well as to real fires.

Findings

In all of the false alarm tests the multi-sensors, on average, operated after the smoke detectors. It was generally found that the more sophisticated the multi-sensors were, the less prone they were to common causes of false alarms, whilst their ability to detect fires was not compromised.

Impact

This research has led to further work with multi-sensor detectors manufacturers to perfect the false alarm tests. Once completed, these will support the development of a Loss Prevention Standard (LPS) and codes of practice for smoke and multi-sensor detectors.

Developing test methods to assess video flame and video smoke detectors

Video fire detectors emerged as a new means of fire detection around 15 years ago, particularly in large indoor spaces such as in atria, warehouses and industrial complexes.

A video detector is alerted to fire by identifying – though analysis by complex algorithms – the characteristic signatures of smoke or flame within its camera’s field of view. There are two detector types, video flame detectors (VFDs) that recognise flaming fires, and video smoke detectors (VSDs) that are alerted by moving smoke. Their ability to ‘see’ flames or smoke (provided there is direct line of sight) enables a quicker response than generally achievable by traditional detectors, and can also provide a visual verification of fire.

Collaborative research programme

A BRE Trust supported research programme was established by BRE, in collaboration with the FIA and video fire detector manufacturers, to develop these tests. The group has developed methods for bench testing and full-scale fire testing of these systems, to gain the necessary underpinning knowledge on performance capabilities. It is now expected that these methodologies will support the development of a test standard and associated code of practice

Suppressing biomass fires using wetting agents

Biomass fuels derived from organic matter, used to generate heat and/or electricity, are typically stored in large outdoor piles or waste processing plants. In some circumstances they can ignite and may take a long time to control, causing severe environmental damage. The Fire Industry Association had identified wetting agents (added to water) that increase the spreading and absorption of water on solid substrates, potentially increasing its effectiveness in extinguishing biomass fires. This research extended that work by performing tests on a larger scale. The methods of suppression had a range of application rates and durations, comparing water only or water plus additive, and the results were shared with the FIA steering group. The variability of the fuel type resulted in issues with developing a consistent repeatable test fire, and therefore further work is required.

Further work

There is interest in repeating this work using coal as a fuel that, while not exactly replicating biomass fuel, is expected to give a more consistent fire. It is anticipated that this methodology will then be developed, leading to a Loss Prevention Standard (LPS) for assessing the effectiveness of wetting agents.

 

 

 

 

For more information on all of these projects including videos please visit the Fire Safety Research website

www.bregroup.com/firesafetyresearch

If you would like to review or send feedback about any of the publications above please visit the Fire Safety Research website and select the relevant project