HYDROGEN FIRE AND EXPLOSION SAFETY HANDBOOK

1. Purpose and Scope

Purpose:
This handbook provides practical safety guidance for engineers, operators, fire teams, and technical managers involved in the production, storage, transfer, and use of hydrogen (H₂).

Scope:
It applies to industrial and commercial facilities handling gaseous or liquid hydrogen, including refuelling stations (HRS). Adjustments may be required to align with local regulations and site conditions.

2. Hydrogen Properties and Main Hazards

• Hydrogen is extremely flammable, colourless, odourless, and lighter than air.

• It has a wide flammability range (4–75%), very low ignition energy, and a nearly invisible flame in daylight — increasing detection and response difficulty.

• Technical hazards include jet fire, fireball, hydrogen embrittlement, high-temperature hydrogen attack (HTHA), and metal dusting corrosion.

• These hazards are prominent in SMR/ATR/POX reformers and other high-temperature, high-pressure systems.

3. Risk Management Principles (ALARP Approach)

1. Elimination / Reduction: Avoid unnecessary hydrogen use; choose inherently safer technologies.

2. Engineering Control: Implement mechanical and automatic safety systems (PRV, vent stacks, F&G detection).

3. Protection & Mitigation: Create isolation zones, fire barriers, evacuation paths, and emergency response plans.

4. Safe Design Requirements

4.1 Applicable Standards

Key standards include: ISO 19880, ISO 14687, NFPA 2, GB 50516, GB 50177, and AIGA guidelines (e.g., AIGA 045/07, AIGA 110/20).
Local regulations must always take precedence where applicable.

4.2 Vent System Design

• Design parameters: elevation, vent diameter, release direction, and analysis of flammable clouds or jet fire zones.

• Classification: distinguish between process vent (purge) and emergency vent (PRD).

• Location: vent outlets must discharge vertically upward and away from personnel or ignition sources.

• Performance verification: evaluate dispersion modelling for worst-case scenarios to confirm safety distances.

4.3 Liquid Hydrogen (LH₂) Systems

• Never allow water to enter vent pipes; ice blockage can cause overpressure and vessel rupture.

• When LH₂ is released and ignites, spraying water may worsen conditions by freezing vents and trapping pressure.

4.4 Safety Distances for Hydrogen Refuelling Stations (HRS)

• Determine distances according to ISO 19880, NFPA 2, or GB 50516, depending on station configuration.

• Firewall structures must not be used to reduce required separation distances.

5. Fire and Gas Detection Systems

• Design detection networks according to AIGA 110/20 and ISO 26142 (Hydrogen detection apparatus).

• Install detectors near compressors, valves, manifolds, storage tanks, and dispensers.

• Maintain periodic calibration, performance testing, and documentation.

• Integrate gas and flame detection into emergency shutdown (ESD) logic where applicable.

6. Ignition Source Control

• Provide grounding and bonding for all fixed and mobile equipment to prevent electrostatic discharge.

• Define hazardous area classifications (Ex zones) and use appropriately certified electrical equipment.

• Control potential ignition sources such as hot surfaces, mechanical sparks, or non-Ex devices.

• Note: “Ignition suppression” systems exist but cannot fully eliminate ignition risk — engineering judgment is essential.

7. Safe Operation and Procedures

7.1 Operational Rules

• All personnel must be trained on hydrogen properties, venting behaviour, and emergency response actions.

• Implement a strict Hot Work Permit system for welding, grinding, or cutting near hydrogen equipment.

• Enforce Lock-Out/Tag-Out (LOTO) during maintenance or isolation.

• Conduct pre-startup safety reviews (PSSR) after any system modification.

7.2 Vent Fires and Lessons Learned

• Many vent fires are safer to let burn until hydrogen supply is safely isolated.

• Operators should not attempt to extinguish vent flames unless the situation poses greater risks.

• For LH₂ vent fires, never spray water — freezing can block vent lines and cause catastrophic overpressure.

• Personnel must maintain distance, monitor from safe zones, and wait for technical instruction from the control room or emergency lead.

8. Firefighting and Emergency Response

8.1 Actions for Gas Leak or Vent Fire

1. Raise the alarm and notify emergency response teams.

2. Evacuate the area upwind; maintain a safe exclusion perimeter.

3. If the vent fire is stable and non-propagating, allow it to burn and isolate the hydrogen source.

4. If fire spreads, trained firefighters may apply cooling to adjacent structures — never direct water jets at LH₂ vents.

8.2 Prohibited Actions

• Do not spray water directly onto vent flames or LH₂ outlets.

• Do not allow untrained personnel to approach vent fires.

• Do not restart hydrogen flow before full inspection and clearance.

9. Maintenance and Material Integrity

• Schedule regular inspections for PRVs, vent stacks, compressors, valves, and gas detection systems.

• Replace or service equipment per manufacturer recommendations.

• Monitor for embrittlement, HTHA, and metal dusting at high-stress areas.

• Keep maintenance logs and inspection certificates for regulatory compliance.

10. Training and Drills

• Conduct hydrogen safety and emergency response training for operators, maintenance teams, and security staff.

• Organize emergency drills at least once or twice annually.

• Incorporate lessons learned from incidents into updated operating procedures.

11. Labeling, Documentation, and Compliance

• Use standardized warning signs (e.g., “Flammable Gas,” “Hydrogen – UN1049”).

• Keep Safety Data Sheets (SDS) accessible at all hydrogen handling areas.

• Maintain inspection, calibration, and training records.

• Comply with applicable standards (ISO 19880, ISO 14687, NFPA 2, GB 50516, GB 50177) and local safety codes.

Appendix A – Daily Pre-Operation Checklist

• Fire & Gas detection system: operational status OK/Not OK.

• Pressure and temperature gauges: within safe range.

• PRV and vent piping: no blockage or visible damage.

• Work area: free of combustible materials.

• Operators: confirm understanding of emergency shutdown.

Appendix B – Quick Emergency Response Guide

1. Activate the alarm system and evacuate immediately.

2. Notify the control room and fire brigade.

3. If vent fire is contained, let it burn; isolate the hydrogen source when safe.

4. Avoid water contact with LH₂ vent systems.

5. Re-enter the area only after authorized clearance.

Appendix C – Periodic Maintenance Checklist

• Calibrate hydrogen gas detectors (record date and results).

• Inspect and function-test pressure relief devices (PRVs).

• Examine LH₂ vent lines for icing or obstruction.

• Inspect materials for cracks, deformation, or signs of embrittlement.

• Verify grounding and bonding continuity.

Conclusion

Hydrogen handling presents unique fire and explosion challenges due to its physical properties. With proper system design, rigorous operation, and continuous training, risks can be effectively managed. Adherence to recognized standards and regular safety reviews remain the foundation of hydrogen safety.