Target gas detection system with rapidly regenerating optically responding sensors

Abstract

The present invention provides an apparatus and method for determining the concentration and/or hazard from a target gas by means of optically monitoring one or more sensors that responds to the target gas by means of an optical change. The apparatus comprises a photon source optically coupled to the sensor and the photon intensity passing through the sensor is quantified by more than one photodiode in a system, so that the photon flux is a function of at least one sensor's response to the target gas, e.g., transmits light through the sensor to the photodiode. The photocurrent from the photodiode is converted to a digital sensor reading value proportional to the optical characteristics of the sensors and is loaded into a microprocessor or other logic circuit. In the microprocessor, the sensor readings are essentially differentiated to determine the rate of change of the sensor readings. The rate of change information is used to trigger an alarm condition indicative of a predetermined level and or hazard of sensed toxins. In addition a preferred method to meet the BSI CO Standard is described using two sensor systems and two sensor on different sensitivity within one housing. The two separate sensor housing uses two LEDs and two photodiodes while the single housing dual sensor uses one LED and two photodiodes. The novel two sensor method to meet the BSI CO standard may not necessarily incorporate a digital display.