SMOKE CONTROL ADVICE
Although Centurion don't sell systems, we do provide expert advice on design and calculations so that your project meets the needs of both the end user and the responsible authorities.
Centurion have carried out smoke calculations on Private Care Trusts, Schools, Leisure Centres, Enclosed car parks and many public buildings with atria and escape walkways. Smoke control systems, which include smoke ventilation and smoke containment, save lives and help protect property. Such systems (sometimes known as fire ventilation) come in many forms and range in complexity, but there are many benefits of a well-designed smoke control system during a fire:
Escape and access routes are kept free from smoke,
Fire fighting operations are facilitated,
Flashover is delayed and/or prevented, and the risk of the fire developing further is reduced,
The contents of the building are protected,
A reduced risk of damage to the building.
The Components of Smoke Control Systems
Smoke control systems can include powered and natural smoke and heat exhaust ventilation systems, smoke containment and car park ventilation systems. Components (smoke ventilators, smoke barriers, smoke ducts, smoke dampers, inlet ventilators, etc) should comply with the BS EN 12101 series of standards where these apply.
Smoke and Heat Exhaust Ventilation
Natural or powered smoke and heat exhaust ventilation systems (SHEVS) remove smoke from the building allowing escape routes and fire fighters’ entry routes to be kept clear of smoke and reducing damage to the building. Dampers and duct work are also often integrated into the scheme.
Smoke containment systems prevent the movement of smoke and heat from one area to another. These take the form either of physical barriers such as smoke curtains or fire curtains, or as pressure differential systems, also known as pressurisation systems.
Car Park Ventilation
Enclosed or underground car parks need smoke clearance ventilation to assist firefighting operations. These are often combined with fume ventilation to prevent the build-up of vehicle exhaust gases in normal day to day use of the car park. The system elements may include louvres, dampers, powered smoke extraction units, induction fans and impulse fans.
Smoke and Heat Exhaust Ventilation Systems
Smoke and heat exhaust ventilation systems, also known as "SHEVS" are natural or powered systems to remove smoke from a building allowing low level escape routes to be kept clear of smoke and reducing damage to the building.
SHEVS comprise three main components: the exhaust ventilators, needed to remove the smoke; smoke barriers, needed to limit the spread of smoke while it remains in the building; and inlet ventilators, needed to allow fresh air in to replace the smoky air removed by the exhaust ventilators.
Dampers and ductwork are often integrated into the scheme.
Natural vs Powered Ventilation
A choice has to be made between natural or mechanical ventilation. Natural smoke ventilation uses the natural buoyancy of the hot gases to drive the smoke flow through the ventilators. Such systems often have a dual function and provide both smoke ventilation and day to day ventilation. By contrast powered smoke ventilation relies on mechanical extraction through fans.
Where the roof space is extensive, it’s necessary to limit the spread of smoke within the roof space. This requires high level smoke barriers to divide the roof space into discrete smoke reservoirs. These barriers may be fixed or automatic smoke curtains or heat resistant boards or glazing. Barriers are also often used in complex buildings such as shopping centres and atrium buildings to control the flow of smoke into the mall or atrium.
The height of the clear layer below the smoke is critical. It needs to be high enough to protect property and escape routes and to ensure that fixed smoke barriers will not adversely affect building usage while being kept as low as possible to minimise the cost of the smoke control system.
A supply of replacement air is essential. As smoke and gases are extracted, sufficient air needs to take their place. Otherwise the building will become depressurised and the smoke ventilation system will become ineffective. Air supply may be from natural ventilators in smoke reservoirs remote from the fire or from dedicated low level air inlet ventilators or automatic doors.