A smoke and heat exhaust ventilation system removes smoke from a building so that low-level escape routes stay clear, and it reduces damage to the building. It is a designed system of several parts working together, not just a roof vent.
Three core parts
- Exhaust ventilators remove the smoke.
- Smoke barriers limit how far smoke spreads while it is in the building. In large roof spaces, high-level barriers divide the space into separate smoke reservoirs. They can be fixed or automatic smoke curtains, heat-resistant boards or glazing.
- Inlet ventilators admit fresh air. Dampers and ductwork are often part of the scheme.
Natural or powered
Natural systems use the buoyancy of hot gases to push smoke out through the ventilators. They can serve a dual role, also giving everyday ventilation. Powered (mechanical) systems use fans to extract the smoke.
The clear layer
The height of the clear layer under the smoke is the critical design quantity. It has to be high enough to protect property and escape routes without hurting the normal use of the building, and as low as practical to keep the system cost down.
Do not forget replacement air
Without enough air coming in, the building depressurizes and the system stops working effectively. Replacement air can come from natural ventilators in smoke reservoirs remote from the fire, from dedicated low-level inlet ventilators, or from automatic doors.
Standards that apply
EN 12101-2 specifies requirements and test methods for natural smoke and heat exhaust ventilators, with performance and reliability requirements so they manage smoke and heat in a fire. Fire detection and alarm systems, EN 54 and ISO 7240, are relevant when the ventilation is triggered automatically.
Related
See our smoke and heat extraction systems page, the smoke ventilation guide and the Mercor smoke vent configurator.
Sources
- Smoke and heat exhaust ventilation systems (Colt)
- Understanding EN 12101-2:2017 smoke control requirements (SNV)