Quick Hits

Episode 2: Pits, Floor Levels & Lighter-Than-Air Fuels (511.5(C) – 511.5(D))

SLIDE 1 (HOOK / COVER)

⚡ NEC Quick Hit: Garage Pits & Hydrogen Safety (Part 2) ⚡

How far up the wall does a hazardous location extend in a major repair garage? What are the rules for hydrogen and natural gas vehicles? Let's check Table 511.5(C)! 👇

SLIDE 2 (BELOWGRADE PITS & FLOOR LEVELS)

Classifying Lighter- and Heavier-Than-Air Areas:

• Service Pits: Unventilated pits or below-grade work areas are classified as Class I, Division 1 (or Zone 1). Providing ventilation of at least 1 cfm/sq ft with suction near the floor drops the pit to Division 2 (or Zone 2).

• Above Grade Level: In major repair garages where Class I liquids or heavier-than-air gases are transferred, the classified area extends up to 450 mm (18 in.) above the floor level for the entire room.

SLIDE 3 (LIGHTER-THAN-AIR FUELS: HYDROGEN & NATURAL GAS)

Ceiling-Level Hazards:

• The 18-Inch Ceiling Rule: Where vehicles using lighter-than-air gaseous fuels (such as hydrogen and natural gas) are repaired or stored, a Class I, Division 2 (or Zone 2) hazardous location extends within 450 mm (18 in.) of the ceiling.

• Ventilation Exception: This ceiling hazard can be made unclassified by providing continuous ventilation of at least 1 cfm/sq ft with suction taken from within 450 mm (18 in.) of the highest point in the ceiling.

SLIDE 4 (WRAP-UP)

💡 Apprentice Pro-Tip: Stock rooms and switchboard rooms adjacent to repair garages can be completely unclassified if they are separated by an unpierced solid partition or mechanically ventilated at four or more air changes per hour!

💬 Save this post for your next industrial automotive facility layout!

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