Mechanical smoke extract systems are utilised in taller buildings, generally above 18m and provide greater escape travel distances via reduced size smoke shaft dimensions.
Smoke is generally extracted from the communal escape corridor to atmosphere by a fan set at roof level via a vertical smoke shaft. Replacement air to equalise pressure is provided via the escape stair, AOV’s located within the corridors or a natural/mechanical air inlet shaft.
Mechanical systems fall outside of the prescriptive Approved Document B methodology therefore require a fire engineered design produced by a smoke ventilation specialist that possesses the required professional capabilities and design liability insurances.