occupation carbon oxide test kit & detector, infrared & odourless Gas, stick on carbon oxide detector secure & at ease to use, more reactive than physical science detectors & provides straight & tried and true results, replace sensor button every 6 x months, un-opened sensor buttons shelf life is 3 years, groovy for use in boats, airplanes, RV 's & automobiles, includes : detector & 2 reclaimable sensor buttons, laboratory tested for accuracy.