One thing all portable gas detectors have in common is alarm tones. One alarm tone is used to indicate gas hazards, albeit with varied frequency or volume for Low/High/TWA/STEL warnings. An alarm for carbon monoxide sounds the same as an alarm for Lower Explosive Limit, oxygen, and hydrogen sulfide.
Hydrogen Sulfide (H2S) is really prevalent here in the south/southwest, but also is becoming more prevalent in other areas where oil and gas exploration is taking hold in light of the U.S. trying to break our dependence on foreign oil reserves.
