Mechanical Supplies

Non-return/pressure relief Dampers

About

Gravity-operated backdraught and pressure relief dampers whose lightweight blades open with forward airflow and fall closed when the fan stops. Counterbalanced versions are set to crack open at a defined room pressure.

Application

Fitted at the discharge of toilet, kitchen and car park extract fans in a common duct, so that when one fan is off the others do not blow back through it. Pressure relief versions are used on gas suppression rooms and on stair pressurisation systems, where they dump excess air once the door-opening force limit would otherwise be exceeded.

Standards & Reference 5 cited

AMCA 500-D
The laboratory method for testing dampers: air performance and, critically, leakage. Leakage class is what a smoke control or energy calculation depends on.
AMCA 511
The certified ratings programme for air control devices: dampers and louvres carrying a verified rather than a claimed rating.
NFPA 92
Smoke control systems: the design and testing of systems that keep smoke out of escape routes.
UL 181
Factory-made air ducts and air connectors: the listing a flexible or fabricated duct carries.