In our Optimax and SWG 100 units the O2 cell will last between 4-6 years while the H2S and CO cells will last 4-5 years. The CO2 and CH4 cells will last the lifetime of the analyzer. For the GEM 5000 the lifespans are 3 years for the O2 cell and 2 years for the H2S and CO cells. The CO2 and CH4 cells will last the lifetime of the analyzer. Keep in mind the lifetime of the analyzer and NDIR components is highly dependent on the sampling environment, attention to maintenance and proper use of the unit. Moisture in the unit and on the board can negatively impact the reliability and lifespan of the sensors