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Published on 07 April 2021 16:28

Key Considerations When Specifying Natural Smoke and Heat Exhaust Ventilators (NSHEVs)

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Key Learning outcomes
  • How smoke behaves in a building fire
  • The role of NSHEVs in protecting building occupants
  • Compliance requirements for NSHEVs
  • Design options to consider when specifying NSHEVs
  • Specifying the correct ladder for NSHEVs
  • Safety and sustainability considerations
Natural Smoke and Heat Exhaust Ventilators (NSHEVs), more commonly known as smoke vents, are installed in the roof to provide essential ventilation in the event of a building fire.
They open by sensors, or remote control, to exhaust smoke and noxious fumes.
The primary function of a NSHEV is to make a dangerous situation safer, with its installation suitable across a diverse range of building typologies and industries, from healthcare and education, to industrial and commercial.

NSHEVs can also provide a means of access for maintenance professionals who may be conducting essential works on the roof.

1.0 Smoke kills, not fire

It is a common misconception that the biggest threat to life in a building fire is from the flames. However, it is the silent black smoke that is the greatest threat to life.

As a fire develops inside a building, it burns the oxygen in the air, removing most of the available oxygen as part of ‘incomplete combustion’, which in turn produces toxic and potentially deadly carbon monoxide.

When a fire ignites in an enclosed space, the smoke rising from the fire gets trapped by the ceiling. It then begins to spread, forming an expanding layer that leaks into any gaps in the floors or walls. This can lead to individuals becoming disorientated, with their vision becoming increasingly clouded, hindering safe evacuation. A fire spread by convection is the most dangerous, causing the largest number of injuries and deaths.

The installation of smoke vents in appropriate locations around a building will protect occupants in the event of a fire by preventing the excessive build-up of smoke and noxious fumes. This subsequently reduces the risk of smoke inhalation, horizontal fire spread and secondary ignitions as the smoke is quickly exhausted, enabling firefighters to safely enter the building to tackle the blaze and building occupants to exit quickly.
Linear actuators open the smoke vent covers to the fire open position of 140 degrees within 60 seconds
Linear actuators open the smoke vent covers to the fire open position of 140 degrees within 60 seconds
 
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