Patent ID: 7335885

Claim:
A fire detector, comprising: an NDIR sensor that generates a detector signal based upon an active source and at least one absorption band selected from the group consisting of a 15.1μ absorption band of CO 2 , a 6.27μ absorption band of H 2 O and a 4.67μ absorption band for CO; and a signal processor which receives the detector signal and generates an alarm signal to warn of a fire when a preselected criterion is met; wherein the NDIR sensor is comprised of: a waveguide sample chamber with at least one opening covered by a thin filtering membrane that allows CO 2 and H 2 O molecules to diffuse freely into and out of the sample chamber but rejects dust and smoke particles from entering the sample chamber; a heat exchanger thermally connected to the sample chamber with at least one opening covered by at least one second thin filtering membrane that allows preselected molecules to diffuse freely into and out of the heat chamber but rejects dust and smoke particles from entering the heat exchanger; and an infrared components assembly that houses the active source and a detector which is thermally coupled to an end of the sample chamber; and wherein the at least one absorption band is the 6.27μ absorption band of H 2 O, the at least one second thin filtering membrane allows H 2 O molecules to pass through it and inside surfaces of both the sample chamber and the heat exchanger are coated with a hydrophobic coating to prevent condensation of H 2 O molecules.