In situ gas filter correlation: photoacoustic CO detection method for fire warning

Common photoacoustic gas detection systems have high sensitivity but they are not so suitable for in situ gas detection in fire situations mainly because of their poor real-time performance. Infrared absorption measuring systems using gas filter correlation technique are capable of in situ uses. However, their sensitivity is relatively lower. This paper presents an in situ method combining both techniques to realize sensitive gas detection for fire warning. CO was here used as the characteristic indicator for a fire. An additional absorption path was set as the measuring space between the broadband infrared source and the photoacoustic cell. The photoacoustic cell was filled with CO gas to work as a gas filter and would produce an initial photoacoustic signal when the light hit the gas. Once the gases to be measured pass through the path, the CO component will reduce the radiation that reaches the cell at specific wavelengths and attenuate the initial photoacoustic signal. (C) 2005 Elsevier B.V. All rights reserved.