This fire door retainer is an easy to use, battery operated sound sensor device which complies with all British standards, EC directive, UK workplace regulations and is approved by the Fire Brigade. The sensor holds a fire door open until a fire alarm sounds, when it will automatically release the door, thus reducing the spread of fire or smoke. There is a foot operated manual release and adjustment operation for manual closing and opening of the door. Holds a fire door open until a fire alarm sounds Sound sensor device will automatically release the door Manual release and adjustment operation possible Meets all British Standards, EC Directives & UK Workplace Regulations Dimensions: 195x45mm (WxD) Batteries included Colour: Black