Analysis chamber for ventilation and air conditioning ducts. Operating principle by Venturi tube, sampling method, single pipe with dual conduit for air aspiration and expulsion. Intelligent monitoring circuit that constantly controls and regulates sensitivity, to ensure optimal operation. Protection rating IP65. Casing in ABS. The device is equipped with a conventional detector, stand-alone operation. Signaling outputs: alarm relay and fault relay with changeover contact. Certified EN 54-27. The analysis chamber must be equipped with a sampling pipe of suitable length.