Verification of Accuracy & Related Terminology With so many reasons why a sensor can lose sensitivity and given the fact that dependable sensors are critical to survival in a hazardous environment, frequent verification of sensor performance is paramount. There is only one sure way to verify that a sensor can respond to the gas for which it is designed. That is to expose it to a known concentration of target gas and compare the reading with the concentration of the gas to ensure that it is within a manufacturer’s recommended tolerable limits. This is referred to as a calibration check or bump test. This testis very simple and takes only a few seconds to accomplish. The safest course of action is to do a calibration check or bump test prior to each day’s use. WARNING The Canadian Standards Association (CSA) requires the instrument to undergo calibration when the displayed LEL value during a bump test fails to fall between 100% and 120% of the expected value for the gas. It is not necessary to perform a full calibration (adjustment) unless readings for LEL and toxic gases/vapors are outside of the range of 90% to 120% of the expected value. For oxygen, the acceptable range is considered to be ±0.5% vol, so 20.4% to 21.4% O in ambient clean air or via application of zero air. Further for oxygen, for application of Honeywell Analytics 18.0% O balance gases, the reading should again be within ±0.5% vol, so 17.5% to 18.5% O2.