Electrical

Great care should be taken in the design of hydrogen systems to minimize the probability that an electric spark will ignite any hydrogen. Precautions include the following:

• All hydrogen equipment should be bonded and grounded
• Vent fans should be constructed with non-sparking blades (typical: aluminum or plastic).
• Areas with potential hydrogen ignition sources should be controlled following hazardous area guidance in an authoritative source such as NFPA 70, National Electric Code (NEC), Article 500 and EN 60079-10-1: ATEX Standard and Classification of Areas with Presence of Gas (ATEX).
• Electrical components for a hydrogen system should follow Class 1, Division 1 or 2, Group B of the NEC or as required by ATEX.
• Equipment not rated for hazardous environments should be located outside the area classified as hazardous.
• Application of ventilation may change the electrical requirements.
• Walls, ceilings, or floors may provide a separation between classified and non classified areas subject to specific design criteria.

Specific requirements are described in the standards referenced by the jurisdiction where the facility is located. Below is an example for hydrogen gas at locations that reference NFPA 70 National Electric Code:

• Class 1: locations in which flammable gases or vapors are or may be present in the air in quantities sufficient to produce an ignitable mixture.
• Division 1: flammable or explosive mixtures may exist under normal operating conditions, or during maintenance (leaks), or because of system breakdown/faulty operation of equipment.
• Division 2: flammable or explosive mixtures are only present under abnormal conditions (i.e., accidental rupture or breakdown of the containment vessel), or systems where ignitable concentrations are prevented by positive mechanical (active) ventilation, or systems adjacent to Class 1/Division 1 locations where vapors might migrate.
• Example from NFPA 497 Classification of Flammable Liquids, Gases or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas

• Guidance can also be found in IEC 60079-10 Electrical apparatus for explosive gas atmospheres - Part 10: Classification of hazardous areas.

References

NFPA 497, Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas

NFPA 70, National Electrical Code

EN 60079-10-1: ATEX Standard and Classification of Areas with Presence of Gas (ATEX)

IEC 60079-10 Electrical apparatus for explosive gas atmospheres - Part 10: Classification of hazardous areas