The Overpressure Blast Valve Type A 483 – LA 600 is a special valve with an integrated blower that enables ventilation of the protected room requiring higher air circulation (ex: toilets) in peace time. It used to stop explosive/implosive blast waves from entering a shelter or secure room, as well as to regulate the air pressure inside the space. The valve, normally closed, allows for an airflow rate of 150-600 m³/h (89-355 cfm). It is maintenance-free and withstands heat and corrosion. The springs are manufactured from special stainless steel and all steel parts are phosphate treated and finished with a powder coating.