Mobility scooter fires: Sprinklers can save lives
London housing provider, Lewisham Homes, has partnered with the London Fire Brigade, the Building Research Establishment (BRE) and British Automatic Sprinkler Association (BASFA) to carry out world first experiments in fire safety. The tests examined how effective residential sprinkler systems are at suppressing mobility scooter fires.
The general increase and use of mobility scooters has presented challenges to housing providers throughout the UK about how the risk of fire associated with these vehicles should be managed.
Steve Kilden, Fire Safety Advisor for Lewisham Homes said:
‘A growing number of people need to use mobility scooters. Because of this we’ve had to look at where our residents can safely store and charge their scooters and how we can reduce the fire risk.
We’re aware there have been a number of fires involving mobility scooters reported and this risk is recognised by fire and rescue services and other agencies.
Mobility scooters come in various sizes, materials and designs. The introduction of an unknown level of fire loading into a building presents a high level of concern and potential obstruction to the means of escape. The risk of an electrical fault occurring whilst the batteries are being charged or from deliberate ignition has to be seriously taken into account.
With the recent use of lithium-ion batteries instead of lead-acid batteries to power mobility scooters, the hazard is increased due to the battery’s unpredictable and highly volatile reaction when subjected to heat. The risk of explosion is a real possibility’.
Lewisham Homes has considered and provided different ways for their residents to store their mobility scooters, including purpose built external storage areas. The provision of alternative storage space does not however offer the close proximity which residents want or need to access their scooters.
This difficulty in finding an answer to safely and conveniently store mobility scooters inspired the housing provider to re-think their approach. Could sprinkler systems installed within sheltered housing schemes for older people offer a better solution?
Steve Kilden told us:
‘We asked the BRE to help us identify whether sprinklers, combined with other safety measures, would support our aim to allow residents to store and charge scooters internally within dedicated communal areas’.
Lewisham Homes brief to the BRE was to assess how effective retro-fitted domestic sprinklers systems are at containing or extinguishing a mobility scooter fire. The outcome of the experiment would assist Lewisham Homes in deciding whether to allow the internal storage and charging of mobility scooters within their housing.
Plans of the proposed storage areas together with the designs of the sprinkler systems installed at a number of sheltered schemes were provided to the BRE.
Domestic Sprinklers, who retrofitted the sprinkler systems, had confirmed these installations were carried out to the relevant British Standard.
The BRE constructed a life-sized mock-up of a shared room in one of the housing schemes using the same sprinkler arrangement.
The particular room layout used for the experiment was chosen because it presented the most challenging conditions, with the area covered by a single sprinkler head.
A textile strip soaked in a small amount of accelerant was ignited and placed close to the scooter’s battery compartment to simulate a fire started by an electrical fault.
For both experiments the door to the mock-up compartment was kept open because this would create even more severe conditions and allow those present to observe what was happening in real time.
The scooters were not charged or plugged into the electricity mains during the experiments.
The experiments were planned to continue for 30 minutes after the sprinklers activated. This was agreed with Lewisham Homes as being the minimum period for which the domestic sprinkler systems are designed to operate.
Temperatures during the experiment were measured by thermocouples fitted on trees, each fixed at various heights and in different locations within the compartment. This allowed for accurate temperature readings to be recorded around the mock-up room during the fire.
The first experiment involved a single mobility scooter with a standard lead-acid battery which was placed in the corner of the mock-up room at the furthest distance from the sprinkler head. The seat of the fire was set to replicate a fire starting within the battery compartment of the scooter.
After about two minutes black smoke started to emerge from the room. After 5 minutes the fire was seen to grow, with flames spreading to the seat of the mobility scooter which caused the temperatures to significantly rise. After 6 minutes the battery housing was well alight and large volumes of hot, thick black smoke were emerging. At 6 minutes the gas layer next to the sprinkler head was recorded at 68°C and within a further 30 seconds the sprinklers started.
Almost immediately after the sprinklers started, the thick black smoke transformed into plumes of grey smoke which meant that no more useful visible observations could be made.
The sprinkler was turned off after 3 minutes to see if the fire had been supressed. Soon after shutting down the sprinkler, it was apparent that the fire started to redevelop and, after 9 minutes from ignition, the fire continued to grow and completely engulf the scooter. Temperatures within the room by this time had reached a staggering 780°C. After 11 minutes 30 seconds the scooter fire was manually extinguished.
The second experiment involved three mobility scooters, one of which was fitted with a lithium-ion battery. The scooter was placed in the corner of the room. To imitate an even more challenging incident, the two remaining scooters were positioned close to the first and in such a way as to shield the initial scooter from the sprinkler head spray pattern.
A new sprinkler head and cover was fitted following the first experiment.
The fire was ignited in just the scooter containing the lithium-ion battery because, except in the case of arson, it was considered highly unlikely a fire would develop in more than one scooter at the same time.
Unlike Experiment 1, the fire spread to the seat more rapidly and higher temperatures were recorded at an earlier stage of the experiment. Observers were required to stand in a safe position and away from the room opening due to the unpredictable reaction of the lithium-ion battery. At about 2 minutes 50 seconds the temperature close to the sprinkler head had reached 90 °C and the sprinkler activated.
The sprinkler was left on for 10 more minutes and the experiment was then stopped as it appeared the fire had been supressed or probably extinguished.
Heavy damage was noted to the battery cover and the lithium-ion battery itself but there was no explosion. The fire did not spread to the other two mobility scooters.
These experiments provide the following key learning points:
- Even if two mobility scooters are ignited at similar points using identical ignition sources, the fire behaviour and the speed of temperature rise can be significantly different.
- The sprinkler system did effectively contain both fires before reaching critical stage.
- Additional control measures will need to be considered to mitigate and deal with the large volumes of smoke given off prior to the activation of the sprinkler system.
- With the increase in use of these vehicles and the associated fire risk, education and advice around safe use and storage, including managing an appropriate fire safety regime, is essential.
The experiments were attended by the London Fire Brigade. Dan Daly, Assistant Commissioner for Fire Safety, said:
‘The action already taken by Lewisham Homes to protect older residents by installing sprinklers in their housing schemes should be applauded. Their latest plans around the storage of mobility scooters recognise there is a need to help residents lead independent lives without compromising their safety.’
Working with the London Fire Brigade, Lewisham Homes is using the results of the experiments to help shape fire safe safety provisions for their new build homes, sheltered accommodation, flats and converted properties.
The experiments provide valuable information and can be regarded as a benchmark for the housing and fire safety industries alike.
Catherine Goakes, Interim Head of Health and Safety at Lewisham Homes said:
‘We wanted to find out whether or not sprinklers could successfully supress mobility scooter fires. Our tests have shown that they can. We are proud to be leading on solutions to this current and growing fire safety risk.’
The experiments and their results are part of ongoing efforts by Lewisham Homes to improve fire safety for their residents. The housing provider has invested more than £13 million over the past 7 years to improve fire safety standards. This has included the installation of sprinkler systems, fire alarm systems, fire doors and raising the awareness of fire safety by sharing improved information with residents.
The BRE Global Client Report: Fire experiments on mobility scooters protected by sprinklers and a short film made by Lewisham Homes about the experiments are available to view now.
For more information, go to www.lewishamhomes.org.uk