Friday, January 28, 2005

Fire Suppression Systems

This subject seems to be an example of the human tendency to arrive at a simple solution through diverse and often contradictory interpretations, almost as though intellectuals had been set to work on the task.

Windsor Castle on fire

After the fire at Windsor Castle in 1992 numerous fire suppression system installers and consultants were called in to advise on means of avoiding a repetition of the conflagration. The installers unanimously recommended the installation of sprinkler systems to which the civil servants reacted with horror. The conversation, we are reliably informed was to the following effect: But surely if the sprinklers go off, the contents of the building will be soaked!.....

Well yes, the installers replied. But water damage can be repaired. Fire is all-consuming and the resulting damage is total and final.

This leads us on to the matter of what kind of fire suppression systems are required for archival storage areas.

BS5454 section 6.7.2 tends to advocate installation of sprinkler systems, stating in general, gas systems are only recommended for discrete spaces that can be made airtight. Such airtight spaces are unlikely to be found in most archive buildings, even the most modern. In fact, gas systems are only effective in such places as ships' watertight compartments.

The United States National Fire Protection Association (US NFPA), the world leader in fire protection matters, recommends only sprinkler systems for archives protection. More specifically, it recommends wet systems.

The drawback with gas systems which leads to their not being recommended for archives protection is that gas storage cylinders exhaust themselves quickly, thereby increasing the risk of latent heat rekindling a fire that has been suppressed by their initial operation. By contrast, water sprinkler systems, if connected to the mains as recommended, or at least to a storage tank, operate until such time as the fire brigade turns off the mains valve.

Dry or preaction system valve: the nub of the matter


Of the two types of sprinkler systems, pre-action (or dry) and wet, only wet systems are recommended for archives by the US NFPA. UK service engineers are able to confirm that pre-action systems, activated by a computer, are notorious for failing and in any case when functional are slow to operate. This last point is confirmed by BS5454 Section 6.7.3 note 2 which states the use of pre-action sprinkler systems may reduce the possibility of inadvertent sprinkler discharge but at the risk of a delay in operation. BS5454 however makes no mention of pre-action systems' tendency to fail between service inspections, in other words to be inoperative when the need arises, and higher installation and maintenance costs.

Wet systems work by being permanently charged whereas pre-action (or dry) systems are only charged on activation, hence the delay in operation. This delay is crucial as seconds or minutes at the most (reference the King's Cross escalator fire 1987) make the difference between a smouldering fire and a major conflagration. A fire is more easily suppressed in its early stages.

Record offices operating gas systems include Dorset County Record Office and the Railtrack National Deeds Archive Centre, Gillingham, Kent.

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