Features
Fire suppression

Fire safety and evacuation: Locus of control

Gary Laird and Martin Brennan set out the main features of fire control systems. 

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Image credit: ©iStock/pisittar

As part of the response to the Grenfell fire the issue of fire suppression in all its aspects has been debated long and hard.

The most common option currently is the manual one, which involves someone in the premises knocking down a fire at its incipient stage using one of the extinguishers or fire hoses located in the building. If you expect staff to use manual extinguishers, they should be aware of the equipment’s limitations as well as their own and trained in the safe use and appropriate selection of the current agent – powder, foam, CO2, water – for the type of fire that is being fought.

As the scenario at the start of our Rapid response article using a CO2 extinguisher in a closed space displaces oxygen and puts the operator at risk. (In that example, the supervisor should also have been trained to raise the alarm before attempting to fight the fire.)

Gary-Laird-member-IOSH-Fire-Risk-Management-Group-CommitteeIn the commercial and industrial sectors the use of automatic fire suppression systems goes hand in hand with fire risk management and business continuity. Automatic systems such as water sprinkler and spray systems are widely used in the process industries to protect storage tanks, plant and warehouses.

For lower-risk operations, there is still a strong cost-benefit case for the introduction of a fire suppression system, especially in new-builds where the cost of incorporating suppression is a small fraction of the total build costs. Yet in many new buildings fire suppression is value engineered out of the specification to cut costs.

There is also a common misconception that in the event of a sprinkler system being triggered, all the heads operate simultaneously, risking damage to building contents unaffected by a fire. This is not the case. Systems are commonly zoned and will direct water only where it is needed. Accidental operation of sprinkler systems is also very rare and needs to be balanced by a risk benefit analysis which will highlight the significant advantages to the suppression system.

Suppression systems are most often intended to preserve property, since this is not a primary task of the fire service. However, when the premises are used by vulnerable people, especially in healthcare facilities and residential accommodation for elderly or mobility impaired people, they can assume a critical role in life safety.

In any building with a functional sprinkler system the risk of death, injury and fire loss is dramatically reduced as the system rapidly stops fires at the point of origin even before trained staff can get to the scene.

A more sophisticated set-up comprises smoke detectors and sprinkler activation monitors complemented by alarm call points, all tied to a central monitored alarm panel with provision to call the fire service.

Heads up

Martin-Brennan-member-IOSH- Fire-Risk-Management-Group-CommitteeThe standard for design, installation and maintenance of sprinkler systems in non-domestic buildings in the UK is BS EN 12845 (2015): Fixed Firefighting Systems: Automatic Sprinkler Systems: Design, Installation and Maintenance (bit.ly/2Bo4Y0D).

Once a sprinkler system has been installed it is the building owner’s responsibility to ensure it is in working order. In the UK, reg 17 of the Regulatory Reform (Fire Safety) Order requires the “responsible person” for the premises to ensure fire systems are “maintained in an efficient state”.

BS EN 12845 details the maintenance requirements for a sprinkler system. The standard recommends weekly visual checks of the installation and a test of the water-driven motor alarm. Pumps supplying the sprinklers should also be tested regularly and seasonal checks made to anti-frost measures, plus less frequent inspection of water tanks for corrosion. (Not all sprinkler systems use these facilities; some are fed by mains water where pressure is sufficient.)

More detailed requirements for maintenance and testing of sprinklers is in the free guide TB203 Care and maintenance of automatic sprinkler systems (bit.ly/2AqZBkt), issued by the insurance industry. The bulletin stresses the need for document testing and servicing.

A fire suppression system should be kept under review to check for any changes in building structure, occupancy, storage, heating and lighting that might call for a change in configuration.

If a sprinkler system has to be taken out of service or is shut down for another reason (such as a loss of water supply from a public main), you should notify the fire service and your insurer.

Closed compartments

Fire protection elements in the fabric of the building are designed to contain or slow the spread of a fire. They include fire-resistant materials, including doors, partition walls and floors.

Fire suppressions systems will not work effectively on their own without occupiers being vigilant regarding the compartmentation of buildings, so it is vital that ceiling voids and cavities are suitably protected to reduce the opportunities for fire spread. More basically, fire-resistant doors must not be allowed to remain propped open in normal use.

Compartmentation will help to confine smoke and fire gases to given areas, preventing the spread of fire, and provide the occupants with time to move to a place of safety.

Ventilation systems, such as rooftop-automatically operated smoke bulkheads, provide controlled ventilation of an area and allow for the escape of smoke and gases out of that area and into the atmosphere. Controlling smoke and gases limits and prevents the build-up of hot gases within an area, thus reducing the potential for the thermal energy associated with these hot gases to transfer back into the compartment and sustain the fire. Smoke control mechanisms also considerably increase the visibility for escaping occupants and responding firefighters.

Hot fire gases of a blaze can move swiftly around a building, through air conditioning ducts, for example. Intumescent air transfer grilles allow normal air circulation but swell in a fire to block the vent. Similarly, intumescent surrounds are available for plastic pipes where they pass through the walls and floors of compartments to seal them, for electrical socket boxes and for ceiling-mounted light fittings which expand to filling the fitting apertures and maintain the fire-resistance of the ceiling or wall. These intumescent fittings are commonly 30 or 60-minute fire rated and are covered by the standard BS476-20:1987.

Fire industry specialists, including the members of IOSH’s Fire Risk Management Group, have reflected on the Grenfell Tower disaster. There are lessons for everyone in industry.

The group, which is a member of the Fire Sector Federation, would be happy to advise other IOSH members who want to get in contact - email frmg@ioshnetworks.co.uk.  

Gary Laird is a member of the IOSH Fire Risk Management Group Committee

Martin Brennan is a member of the IOSH Fire Risk Management Group Committee

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