The seminar was organised by the International Water Mist Association (IWMA), which has a specific agenda - to promote the use of water mist, so it is not surprising that the majority of things said from the stage during the day were very much in favour of water mist use, as an alternative to traditional sprinklers. The implication in a few presentations was that sprinklers are old technology, whereas water mist is the future of fire protection.
"How does water mist work?" was the title of the first presentation of the day, and in his opening remarks Erling Mengshoel, from Protect Systems in Norway, apologised to the academics in the room that his presentation wouldn't contain any equations or complicated theories. It didn't contain any significant science either, got the fire triangle wrong (he gave it as "Oxygen", "Fuel load" and "Temperature") and, unfortunately, set the tone for the rest of the day, in that none of the other presentations really got to grips with important questions like where, when and why water mist is better or more efficient at mitigating the effects of fire compared to traditional sprinklers.
To summarise, water mist is a water spray system which uses higher water pressure and different kinds of nozzles from traditional sprinklers, to produce (much) smaller water droplets. These water droplets interact with flames directly, quenching the burning in the gas phase, cooling the volume, and displacing air, effectively pushing the oxygen needed for combustion away from where the burning is happening. So water mist achieves its fire protection aims by cooling and dilution. Traditional sprinklers, on the other hand, achieve their aims by surface wetting - keeping the potential fuel around the fire cool and wet, so that fire spread and growth cannot occur.
Is water mist a kind of sprinkler system? The answer given in this seminar is no, it is not. It is an alternative and rival technology.
Bob Whitely from Tyco UK gave two presentations back-to-back on where water mist is used at the moment, and on the development of a British Standard for water mist, BS 8489, which should be published in the next few weeks. Where are we? Well, water mist is used on only about 3% of land based applications with an active fire protection system. I say "land based" as water mist has a much bigger market share in offshore and marine applications. The agenda of the day, however, was to promote water mist for onshore applications, and try to get engineers, designers, regulators & insurers to consider the possibility of water mist in the other 97% of the market.
Why a British Standard? Well, the answer to that question seems to be that we really want a European or ISO standard, but they are taking so long to develop that someone has to lead the field here, and it might as well be us. Another British Standard, BS 8458, which focuses on residential use of water mist, will also be along soon.
Bob Whitely painted a fairly bleak picture of the regulation and insurance industries with regard to water mist acceptance and approval. He basically said that there are not enough people working in these industries who actually understand fire safety engineering, and so there is a bias towards traditional sprinklers and away from 'novel' systems like water mist, simply because those with the authority to approve such systems are not equipped to make the decision. I noted that when the representative of the insurance industry (Gary Howe, from Zurich Insurance) took the stage an hour later, he did not attempt to rebut this opinion.
Gary Howe's presentation was interesting and frustrating in equal measure. His main point was that if you want to put in a water mist system as an alternative to sprinklers, you have to demonstrate that your system works in each different kind of occupancy in a building you are proposing to protect - in essence, he was saying that you might need to carry out multiple full scale fire tests to demonstrate your system, for use in a single building, if you want insurance approval. That is, use a performance based approach. However, he also made a big deal of the necessity for approved nozzles, approved pumps, approved pipework, etc. That is, a prescriptive approach. Basically if you want to get a water mist system approved you have to jump through many more hoops than if you propose a traditional sprinkler (which is all prescription and no performance-based approval required). You rarely have to demonstrate that a sprinkler will work, it is just assumed to do so.
The rest of the day was a mixture of case studies and presentations from water mist companies saying how great their product is. One presentation from BAFSA spoke about the lack of and need for proper qualifications and training for sprinkler engineers, but as the topic wasn't specifically on water mist, most of the audience seemed to dismiss the message.
The most important questions about water mist are those that were not asked or addressed. Specifically, when should water mist not be used? When are traditional sprinklers better? What are the situations where neither sprinklers or water mist are effective? And so on. I guess I wasn't expecting such questions to be addressing in this forum, but I think there really is a need for discussion and research into these questions.
Yes, water mist can be a great technology for fire protection, and yes, it could be used in many applications currently served by traditional sprinklers. There may even be financial and ecological savings along the way. We already know this. Understandably, the focus of this event was on persuading the building control and insurance industries to approve water mist in cases where it can and should be approved. But I think this agenda would actually be served better by research into and education explaining the territory where water mist reaches the limits of its capabilities.
To summarise, water mist is a water spray system which uses higher water pressure and different kinds of nozzles from traditional sprinklers, to produce (much) smaller water droplets. These water droplets interact with flames directly, quenching the burning in the gas phase, cooling the volume, and displacing air, effectively pushing the oxygen needed for combustion away from where the burning is happening. So water mist achieves its fire protection aims by cooling and dilution. Traditional sprinklers, on the other hand, achieve their aims by surface wetting - keeping the potential fuel around the fire cool and wet, so that fire spread and growth cannot occur.
Is water mist a kind of sprinkler system? The answer given in this seminar is no, it is not. It is an alternative and rival technology.
Bob Whitely from Tyco UK gave two presentations back-to-back on where water mist is used at the moment, and on the development of a British Standard for water mist, BS 8489, which should be published in the next few weeks. Where are we? Well, water mist is used on only about 3% of land based applications with an active fire protection system. I say "land based" as water mist has a much bigger market share in offshore and marine applications. The agenda of the day, however, was to promote water mist for onshore applications, and try to get engineers, designers, regulators & insurers to consider the possibility of water mist in the other 97% of the market.
Why a British Standard? Well, the answer to that question seems to be that we really want a European or ISO standard, but they are taking so long to develop that someone has to lead the field here, and it might as well be us. Another British Standard, BS 8458, which focuses on residential use of water mist, will also be along soon.
Bob Whitely painted a fairly bleak picture of the regulation and insurance industries with regard to water mist acceptance and approval. He basically said that there are not enough people working in these industries who actually understand fire safety engineering, and so there is a bias towards traditional sprinklers and away from 'novel' systems like water mist, simply because those with the authority to approve such systems are not equipped to make the decision. I noted that when the representative of the insurance industry (Gary Howe, from Zurich Insurance) took the stage an hour later, he did not attempt to rebut this opinion.
Gary Howe's presentation was interesting and frustrating in equal measure. His main point was that if you want to put in a water mist system as an alternative to sprinklers, you have to demonstrate that your system works in each different kind of occupancy in a building you are proposing to protect - in essence, he was saying that you might need to carry out multiple full scale fire tests to demonstrate your system, for use in a single building, if you want insurance approval. That is, use a performance based approach. However, he also made a big deal of the necessity for approved nozzles, approved pumps, approved pipework, etc. That is, a prescriptive approach. Basically if you want to get a water mist system approved you have to jump through many more hoops than if you propose a traditional sprinkler (which is all prescription and no performance-based approval required). You rarely have to demonstrate that a sprinkler will work, it is just assumed to do so.
The rest of the day was a mixture of case studies and presentations from water mist companies saying how great their product is. One presentation from BAFSA spoke about the lack of and need for proper qualifications and training for sprinkler engineers, but as the topic wasn't specifically on water mist, most of the audience seemed to dismiss the message.
The most important questions about water mist are those that were not asked or addressed. Specifically, when should water mist not be used? When are traditional sprinklers better? What are the situations where neither sprinklers or water mist are effective? And so on. I guess I wasn't expecting such questions to be addressing in this forum, but I think there really is a need for discussion and research into these questions.
Yes, water mist can be a great technology for fire protection, and yes, it could be used in many applications currently served by traditional sprinklers. There may even be financial and ecological savings along the way. We already know this. Understandably, the focus of this event was on persuading the building control and insurance industries to approve water mist in cases where it can and should be approved. But I think this agenda would actually be served better by research into and education explaining the territory where water mist reaches the limits of its capabilities.