Pressure Relief Damper is used in Modular Operation Theaters, Clean Rooms to maintain positive pressure within the room. Pressure Relief Dampers will be provided in each theatre to prevent of air from clean and dirty areas. Suitably sized air pressure relief damper will be strategically placed, enabling differential room pressure to be maintained and ensure that when doors are opened between clean and dirty areas. Counter-weight balancing system will be provided in the PRD. The PRD will remain closed at pressure below the set pressure and open fully at pressure only fractionally above the threshold pressure.