MSVS is designed to provide mechanical extract of smoke laden air and natural or replacement air inlet. Detection of smoke within the protected lobby will automatically trigger the system. The fire damper will open into the smoke shaft, other dampers are then “locked out” to ensure they stay closed. A fan set compromising duty and standby smoke ventilation fans is installed on the roof, the duty fan will operate to draw smoke through the damper and up the shaft. If this fan fails, an automatic transfer switch will operate the standby fan.
Inlet air is provided by opening a Natural Heat Smoke Exhaust Ventilator (NSHEV) at the head of the protected staircase. Fresh air is drawn through the staircase and door into the protected lobby.
This keeps the staircase free of smoke to allow safe escape for residents and safe access for firefighters. The basic principle of operation is similar for different building configurations, control of the system is adaptable to meet the architects design