Water Mist Fire Suppression Systems for ... - Risk Engineering

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companies, however, the test criteria used bares no resemblance to the fire loadings for the purposes of thisdocument and is inadequate, when compared with the expected practice throughout the fire protection industry.Fire Engineered Building DesignIn addition to the obvious benefits of installing sprinkler protection to protect a premises Approved Document B:Fire Safety Volume 2 - Buildings other than Dwelling Houses and BB100: Fire Safety in Schools offer otherattractive benefits, which will appeal to architects, local authorities, project sponsors and end users.Based on the provision of a fully compliant sprinkler system, it is acceptable to look to reduce other fireprotection measures for both property protection and life safety elements. These include the level of automaticfire detection to be provided and fire resistance of compartments, e.g. from 60 minutes to 30 minutes fireresistance. These reductions can offer significant financial savings which can be offset against the cost of aconventional fire sprinkler system. In addition, unparalleled design freedoms can be achieved, in the form oflarger compartment sizes, e.g. from 800m² to 2000m², extended travel distances and the potential reduction inthe number of fire escape staircases.A significant number of other trade-offs, or design freedoms, exist and the provision of sprinklers can bringunparalleled flexibility in design.The use of water mist systems will not permit the same deviations from the building regulations, as afforded tothe use of sprinkler systems. The main reason for this, is that currently, there is no applicable proven designstandard for water mist systems and, as such, the same level of reliability cannot be assumed.Modern Methods of ConstructionThe desire to create an innovative and sustainable built environment is constantly increasing. The introduction ofsuch schemes as the BRE Environmental Assessment Methods (BREEAM) has charged architects, engineers,designers and end users, with ensuring that their new buildings have a low environmental impact, reducedrunning costs, and demonstrate progress towards corporate and organisational environmental objectives. Due tothis requirement, most new projects are using modern methods of construction to achieve a “very good” or“excellent” rating. This has had a huge effect on the materials used in construction, the type of services providedand as such an effect on the way a building will behave under fire conditions.An example of this is the use of treated or untreatedtimber, which is particularly prevalent in new buildprojects, as it is seen as a sustainable material and hasbeen ethically sourced. This not only includes the use oftimber cladding on the external face of a building as afinish, but also the structural frame and internal walls.
Another example is the insulation of buildings taking many different forms and using alternative materials toachieve high standards of thermal performance. Whilst most of these materials are tested and found to have fireresisting qualities, some being used do not, such as recycled newspaper. In such buildings, the active firesuppression system plays a large role in ensuring that a fire will not lead to a total loss. Sprinkler installations havebeen extensively tested and installed throughout a wide range of differing building types.The testing referred to within the IMO standards for water mist systems is based on the construction of a ship,where each individual room is a relatively small steel fire resistant compartment. The only additional fire loadingsin this instance would be the furnishings within the room and items brought into the space by the occupant. Inmost buildings, regardless of the hazard classification, the fire loading will be significantly higher.Hazard ClassificationSchoolsOriginally, sprinkler installations for schools were deemed to be Light Hazard within BS 5306 Part 2:1990. It soonbecame apparent that the fire loadings within these premises, coupled with the larger compartment sizes beingcreated, meant that this classification needed to be increased. Following the introduction of Technical Bulletin 34– Sprinkler Protection of Schools in July 2003, the classification was increased to a minimum of Ordinary HazardGroup 1, with the condition that this may need to be increased further should there be higher fire loadingspresent. To date, this classification has remained the same and was carried forward into the new EuropeanStandard BS EN 12845 Technical Bulletin 221.What has not remained the same, however, are the buildings being protected by these systems. With the adventof the Building Schools for the Future project and the need to provide innovative and inspiring educationalfacilities for today’s children, these buildings are now taking an appearance more commonly associated withshopping malls and city centre office blocks. As insurers of these premises, we need to take a balanced view ofthe level of fire protection systems, which will be acceptable to ourselves, not only to protect our own bottomline, but also to safeguard the assets and investments of our customers.Generally sprinkler installations within schools are designed as Ordinary Hazard Group 1, although the presenceof areas, such as theatre stages, stock rooms, car parks, plant rooms, etc., would ideally require a higherclassification, typically Ordinary Hazard Group 3. From the outset, one of the main stumbling blocks of achievingsprinkler protection of schools was the size of the water supplies, due to the requirement for 60 minutes ofstored water. This problem was addressed within the Technical Bulletin which permitted 30 minutes of storedwater for Ordinary Hazard Group 1 occupancies, only with the provision of a Fire Brigade inlet connection. Nosuch reduction, in stored water capacity, is currently offered for higher classifications.Due to the safety margins, built into sprinkler installations, we can take comfort in the knowledge that shouldone of these systems be called into action, the additional flows and pressures achieved from the operation of thefirst sprinklers, will inevitably control a fire within its area of origin and in many cases achieve extinguishment.As water mist systems are entirely performance based, with no level of over-engineering, we cannot have thesame faith.
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Water Mist Fire Suppression Systems for ... - Risk Engineering

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