Go here and spend $40: http://store.finehomebuilding.com/building-codes/code-check.html
. It's not enough to just know the NEC. For half the price of an NEC, you get a lavishly illustrated 'Cliff's notes" to the basic codes.
Joe, do you really think you're the first to have concerns about water heaters in garages? I doubt it- since you hail from California, and they've been putting water heaters on pedestals for at least a quarter-century now.
The plumbing code addressed this issue long ago. Water heaters in carports and garages, or that draw their ventilation from them, need to either be on a pedestal, or be of a 'flammable vapor ignition resistant' design. FVIR. Easily found everywhere water heaters are sold - and at a nominal price difference. UL listed and all that stuff.
Oddly enough, I am dealing with this exact situation in my house. Since the place was built (1957) there have been many changes to the requirements for water heaters. Venting, drainage, mounting ... lots of changes. And, if the water heater is in a closet, no storage is allowed there.
No need to re-invent the wheel, and get all worked up about 'classified locations.' The plumbers got there first.