As a best practice, we train instrument users to perform four basic steps in clean air each time they turn their monitor on for use: Verify the battery charge level Zero the monitor Bump test Clear the peaks You should never zero your gas detector unless you know that you are in a clean air environment. Zeroing a device in a contaminated atmosphere can lead to confusion in the resulting readings, and may even mask the readings of potentially dangerous gas concentrations. If clean air is not available—as is common near fires or in smoky areas—you should use zero air (compressed air with impurities removed) to establish a baseline for your monitors. Zero air will not harm your monitors or disrupt sensor function. If you turn on your Industrial Scientific gas monitor and the readings are within acceptable limits, there is no need to zero your monitor.