for air exchange across the entire floor area, and exhaust air shall be taken at a point within 0.3 m (12 in.) of the floor.

(b) ventilation Not Provided. The entire floor area up to a

level of 450 mm (18 in.) above the floor shall be classified as
Class I, Division 2 if the ventilation does not comply with
511.3(C)(1)(a).

(2) Ceiling Areas. Where lighter-than-air gaseous fueled vehicles, such as vehicles fueled by natural gas or hydro gen, are repaired or stored, the area within 450 mm (18 in.) of the ceiling shall be considered for classification in accor dance with (a) and (b).

(a) Ventilation Provided. The ceiling area shall be un- classified where ventilation is provided, from a point not less than 450 mm (18 in.) from the highest point in the ceiling, to exhaust the ceiling area at a rate of not less than 0.3 m 3/min/m2 (1 cfm/ft 2) of ceiling area at all times that the building is occupied or when vehicles using lighter-than-air gaseous fuels are parked below this area.

(b) Ventilation Not Provided. Ceiling areas that are not

ventilated in accordance with 511.3(C)(2)(a) shall be classified
as Class I, Division 2.

(3) Pit Areas in Lubrication or Service Room. Any pit, belowgrade work area, or subfloor work area shall be clas sified as provided in (a) or (b).

(a) Ventilation Provided. The pit area shall be a Class I, Division 2 location where there is mechanical ventilation providing a minimum of six air changes per hour.

(b) Ventilation Not Provided. Where ventilation is not provided in accordance with 511.3(C)(3)(a), any pit or de- pression below floor level shall be a Class I, Division 1 location that extends up to the floor level.

(D) Minor Repair Garages. Where flammable liquids having a flash point below 38°C (100°F) such as gasoline, or gaseous

fuels such as natural gas or hydrogen, will not be dispensed or transferred, the classification rules in (D)(1), (D)(2), and (D)(3) shall apply to the lubrication and service rooms.

(1) Floor Areas. Floor areas in minor repair garages without pits, belowgrade work areas, or subfloor work areas shall be unclassified. Where floor areas include pits, belowgrade work areas, or subfloor work areas in lubrication or service rooms, the classification rules in (a) or (b) shall apply.

(a) Ventilation Provided. The entire floor area shall be unclassified where there is mechanical ventilation providing a minimum of four air changes per hour or one cubic foot per minute of exchanged air for each square foot of floor area. Ventilation shall provide for air exchange across the entire floor area, and exhaust air shall be taken at a point within

0.3 m (12 in.) of the floor.

(b) Ventilation Not Provided. The floor area up to a level of 450 mm (18 in.) above any unventilated pit, below-grade work area, or subfloor work area and extending a distance of

900 mm (3 ft) horizontally from the edge of any such pit, belowgrade work area, or subfloor work area, shall be classified as Class