For Californians,
There has been a change in the wording from 2001 to 2014. 2011 required heating and cooling equipment to be elevated but not clothes dryers. 2014 includes clothes dryers. The plumbing code had that same requirement for gas fired water heaters. Be aware that there is an exception for FVIR water heaters.
2011CMC
307.1 Protection Against Damage. Appliances installed in
garages, warehouses, or other areas subject to mechanical
damage shall be guarded against such damage by being
installed behind protective barriers or by being elevated or
located out of the normal path of vehicles.
Heating and cooling equipment located in a garage and
that generates a glow, spark, or flame capable of igniting
flammable vapors shall be installed with the pilots and
burners or heating elements and switches at least eighteen
(18) inches (457 mm) above the floor level.
2014 CMC
308.1 Protection Against Damage. Gas utilization appliances
in garages and in adjacent spaces that open to the
garage and are not part of the living space of a dwelling unit
shall be installed so that burners and burner-ignition devices
are located not less than 18 inches (457 mm) above the floor
unless listed as flammable vapor ignition resistant. [NFPA
54:9.1.10.1]
308.1.1 Physical Damage. Appliances installed in
garages, warehouses, or other areas subject to mechanical
damage shall be guarded against such damage by
being installed behind protective barriers or by being
elevated or located out of the normal path of vehicles.