Patent ID: 7504959
Filing Date: 2009-03-17
Classification: G01N

Abstract:
1. Apparatus for detecting and confirming that a concentration of a selected gas in a gaseous mixture is at least as great as a predetermined level of concentration, comprising: a conduit for coupling to a gaseous mixture; a sensor for detecting gas in the conduit and generating a signal representative of a concentration of a selected gas present in the mixture; a pump having a controllable flow rate, the pump pumping the gaseous mixture through the conduit at a first flow rate; control circuits coupled to the sensor and the pump, the control circuits determine a first concentration of the selected gas at the first flow rate, and responsive at least in part thereto, causing the pump to pump the mixture at a second, different flow rate, the control circuits determine a second concentration of the selected gas at the second flow rate, the control circuits use the concentration at the first flow rate and the concentration at the second flow rate in establishing the presence of a selected gas condition.