A fleet maintenance facility carries everything an independent repair garage does at larger scale, and adds two things that change the protection picture materially: on-site fueling, and increasingly a mixed fuel fleet. Municipal transit, refuse, school bus, and utility fleets across South Florida have moved substantially toward compressed natural gas, and fuel cell and electric vehicles are entering the same shops.
The critical technical point about gaseous fuels is that they behave in the opposite way to gasoline. Methane, whether delivered as CNG or evaporating from LNG, is lighter than air. So is hydrogen, considerably more so. A leak from a natural gas vehicle rises and accumulates at the ceiling and in roof structure pockets, which is exactly where a facility designed around gasoline vapor has no detection and no ventilation, because all of that was correctly placed at floor level.
That inversion is the single most important thing to get right in a mixed fleet facility. A shop that services both diesel and CNG buses needs floor-level ventilation for the liquid fuel hazard and ceiling-level gas detection with high-level ventilation for the gaseous one. Facilities that converted part of their fleet to natural gas without revisiting the building routinely have the correct provisions for the fuel they used to run and none for the fuel they now run.