In Canada a garage for the storage of more than 3 cars is classified as a hazardous location at or below grade. The idea is that gasoline vapours will sink to the lowest areas or depressions in the floor at grade. The hazardous area extends from below grade to 2 inches above. Ventilation in underground parking areas can also reduce the hazardous location to 2 inches abouve the floor. Of course most garages not open to the air require mechanical ventilation just for Carbon Monoxide. An elevator pit would be classified if the elevator threashold was at the same level as the garage floor. We have a 2 inch curb requirement that can separate the elevator pit from the garage. I understand this classification is not applied to garages where cars are parked or stored but NOT repaired. Is that true? or are parking structures treated special?
The difference is mainly in below-ground structures used for parking compared to repair. Parking is Class 1, Zone 2, two inches above the floor and repair is Class 1, Zone 2, two inches above grade. Two inches above the floor is a minor problem, but two inches above grade probably makes ventilation an attractive alternative.
"(A) Parking Garages. Parking garages used for parking or storage shall be permitted to be unclassified. FPN: For further information, see NFPA 88A-2007, Standard for Parking Structures, and NFPA 30A-2008, Code for Motor Fuel Dispensing Facilities and Repair Garages."