The solid-state lab I slaved in as a grad student had a gas blend that consisted of nitrogen plus about 3% hydrogen. It was called "forming gas" and was used when you wanted a reducing atmosphere but didn't like the idea of exploding furnaces.
Later on when I worked in a lab associated with a fab (actually making money at the time), we periodically had test drills that simulated things like hydrogen leaks. The alarm sound for that was pretty distinctive, kind of a rising/descending whistle. Fortunately I never heard one in a real leak situation.
Fabs use other really nasty gasses and chemicals in addition to hydrogen. Some spontaneously combust in air, some will combust and release arsenic oxide, some are just plain poisonous. We took fire drills and other types of emergency drills very seriously.....
