The output of nearly all non-dispersive infrared (NDIR) gas sensors deployed in the heating, ventilation, and air conditioning (HVAC) industry today cannot maintain their accuracy specifications within six months to a year. Consequently, all installed NDIR gas sensors must be re-checked for accuracy over time at great costs. The purpose of this paper is to advance a novel technique for expeditiously recalibrating such installed NDIR gas sensors without the need for using any gas standards.

Design/methodology/approach
By recognizing the fact that the calibration curve for absorption biased designed NDIR gas sensors comprises two distinct domains, namely an invariant NDIR absorption physics domain and a variant sensor components characteristics domain. By formulating a novel recalibration procedure which corrects only changes that have taken place in the variant sensor components characteristics domain over time, it is possible to recalibrate the sensor very rapidly and remotely via wireless or infrared means using only the gas concentration level surrounding the sensor as a reasonably accurate gas standard.

Findings
Implementation of the currently described recalibration technique to a large number of absorption biased designed NDIR gas sensors has been carried out for over a year in the laboratory. Results of these experiments have unambiguously confirmed the capability and the accuracy of this novel recalibration technique.

Originality/value
The currently presented recalibration technique for absorption biased designed NDIR gas sensors is original and has never been published elsewhere. This technique significantly reduces the maintenance costs, inclusive of labor and material, for installed NDIR gas sensors that require periodic and mandatory accuracy commissioning over time.