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Use of fire doors in buildings -
General requirement of fire doors in individual  occupancies
3.4.6.4 - Standby supplies like DG room if it is installed within the building it should have the 
wall and door of minimum 120minutes rating. 3.4.8.1 - Air conditioning, heating and mechanical ventilation
a) Battery rooms shall also have 120minutes segregation as a compartment 
3.4.8.2 - Air handling unit
a) 3.4.8.2.1 - The requirement is more for smoke control doors
b) 3.4.8.2.2 – walls and doors of shafts, ducts, and room shall be 120min fire rating
c) Smoke and fire dampers to be provided in each shaft zone and floor wise.