Abstract: A device for cleaning the air in welding shops includes a casing surrounding a fan and an electric motor, a mechanical filter upstream of the fan and a filter including active carbon down-stream of the motor. In order to maintain a suitable temperature for the active carbon the air is brought to pass through, or around the motor. A thermal relay is provided to interrupt the current supply to the motor, should the temperature, due to clogging of the mechanical filter and resulting increase of the motor output, be raise to an impermissible level.