The present invention describes a replaceable breath alcohol sensor module that can be replaced with a new pre-calibrated breath alcohol sensor module or re-calibrated. The breath alcohol sensor module requiring calibration can be removed from the body of a Breath Alcohol Testing Device (commonly called “breathalyzer” or “breathalyzer”). The breath alcohol sensor module can be separately calibrated for accurate calculation of “percent blood alcohol concentration” (% BAC) based on breath air samples and then re-installed into the breath alcohol tester or the old breath alcohol sensor module can be replaced with a new pre-calibrated breath alcohol sensor module. The present invention improves upon and/or replacing the current method of re-calibration at a breathalyzer service center.