Patent ID: 7803039

Claim:
A method for controlling air intake into an air conditioned enclosure, comprising: detecting a change in NOx gas outside of an air conditioned enclosure, where the change in NOx gas is determined in relation to a baseline value of NOx gas; detecting an event independent from the change in NOx gas which lowers the baseline value of NOx gas, wherein detecting the event which lowers the baseline value further comprises monitoring hydrocarbon gas outside of the enclosure and correlating the event with a change in hydrocarbon gas outside of the enclosure; correlating the baseline value of NOx gas with a measured value of NOx gas based on upon completion of said event; and determining a change ratio of hydrocarbon gas by dividing a value of hydrocarbon gas recently measured outside of the enclosure by a baseline value of hydrocarbon gas and comparing the change ratio to a threshold value, such that the event occurs when the change ratio is lower than the threshold value.