This is a real long shot and something I just thought of, this morning I arrived at work and one of our server rooms smelt like rotten eggs, a UPS battery had overheated and vented.
Having a Hydrogen Sulfide sensor would be handy from a health and safety perspective. While our UPS all have monitoring this seemed to slip through the cracks.
Hydrogen Sulfide is a poisonous gas so having a system alert to the fact before you enter a room would be nice.