Many people thought there was too much overlapping and inconsistent guidance. There are over 100 fire safety design-related codes and standards – and this is without counting things like methods of test and product specification standards. Despite this quantity there are significant gaps in the coverage.
New proposals are at the centre of a plan to overhaul and streamline the existing guidance. This will be brought together into a single British Standard on the fire safety design of buildings: BS 9999.
The new standard could make services more important in the fire safety approvals process. In particular as it will cover means of escape (drafted by Buro Happold), construction (drafted by Arup Fire), fire safety management (by the BRE's Fire Research Station), and access and facilities for firefighters.
Existing material will be drawn into the standard. This could replace not only the building-type codes in BS 5588, but also publications like Approved Document B, the Home Office guides on the Fire Precautions Act, and many other technical standards and guides. This was not to be a simple cut and paste exercise. What was wanted was a set of principles that could be applied very widely, and yet could be simply stated to avoid ambiguity and undue restriction.
Consultants were commissioned to produce drafts to get the BSI process started. At present the drafts are being edited, then early in 2000 they will be sent for review by interested government departments. If BS 9999 is to replace the current guidance from these departments it must win ministerial approval.
After that, whatever is left of the draft will go to public consultation, followed by the usual BSI committee stages and changes. The standard could reach publication in three years time, although five years seems more likely.
Doubts over the publication date aside, the proposed sections in BS 9999 will have a significant effect on building services design.
Means of escape
The consultants came up with some new ways of categorising building and occupant features which could help to overcome the limitations of current building-type guidance. Instead of applying a single label to a building, they proposed looking at the occupant characteristics in terms of familiarity with the building, their level of awareness, and the level of disability.
This is married to a simple assessment of the fire growth potential for the proposed use of the area, which serves to derive a notional "allowable travel time". This is then used to determine a limiting travel distance and escape route capacity.
A package of minimum fire protection measures has to be provided: a more or less rudimentary alarm system, escape lighting and exit signs. If the occupancy is a higher risk one, the package is a little more sophisticated. However, adding sprinklers or a directive voice alarm system allows the travel time (and therefore travel distance) to be increased. It is proposed to cap the extra travel time that could be bought in this way.
It is too early to say what the increase in travel distance might be. Indeed, it is possible that the whole idea may not survive the standard's development process.
Construction
This part of the draft standard deals with fire resistance, compartmentation, the reaction to fire properties of lining material, fire spread between buildings and important details like cavity barriers and fire dampers.
From the services engineer's point of view, the most significant proposals concern sprinkler systems. For life safety the consultants proposed adding a new class of sprinkler system to the four existing ones described in BS 5306: Part 2. They aimed to specify a system which can maintain a safe environment during the evacuation and, if desired, the initial fire-fighting phases of an incident.
This would typically mean a water supply of 30 minute duration, based on nine sprinkler heads operating, rather than the 16/18 heads for current "ordinary hazard" applications. By reducing the cost of water supply and storage, and increasing travel distance, many more buildings could have sprinklers installed – improving fire safety as a result.
Another benefit of the sprinkler changes would be that the rules on boundary separation distance and unprotected facade area could be ignored for life safety (though not necessarily for property protection).
The other main construction proposal is to take account of ventilation when the fire resistance requirements are being set. This could follow similar lines to the "equivalent time of fire exposure" method described in the Structural Eurocodes. This would cut the period of fire resistance in many instances, in turn reducing the performance requirement for service penetrations of fire resisting construction.
Fire safety management
If fire protection services are to play a more explicit and recognised part in the overall safety of buildings, upkeep and operation will be as important as the original design process.
The threat of legal sanction is all very well as a way of forcing people to take this sort of thing seriously. But what could engineers do to help building management understand the systems they have been given, so that they are properly looked after and operated by successive generations of staff? Management is to be given a high profile in BS 9999. Services engineering will feel the effect as much as any part of the design team.
That said, as a prescriptive standard, BS 9999 will not remove all the problems of application and interpretation of present documents. The initiative still depends on other standards for systems design, product specification and test methods. However new ideas are surfacing that could eventually allow greater recognition of the role of building services in fire safety.
There is still plenty of time to influence the development process.
Source
Building Sustainable Design
Postscript
Anthony Ferguson is with Arup Fire.
