Hydrogen Refueling Ventilation Airflow Calculator

Size ventilation to dilute hydrogen releases during refueling by comparing containment and purge airflow requirements.

Maximum credible leak mass flow during dispensing.
Volume of the canopy, compressor bay, or enclosure.
Target volume fraction cap; default 1% keeps well below the 4% LFL.
Minutes to fully exchange enclosure air after a leak; defaults to 5 minutes.

Preliminary sizing aid. Confirm results with a licensed fire protection engineer and applicable hydrogen safety standards before construction.

Examples

  • 0.08 kg/min release, 950 m³ enclosure, 1% cap, 5-minute purge ⇒ Recommended flow 91.4 m³/min (3,227.7 CFM); containment 95.3 m³/min and 6.02 ACH, purge target 190.0 m³/min.
  • 0.03 kg/min release, 600 m³ volume, allowable 0.8% left blank defaults to 1%, purge 4 minutes ⇒ Recommended flow 61.8 m³/min (2,181.0 CFM); containment 35.8 m³/min with 3.58 ACH, purge target 150.0 m³/min.

FAQ

Why use hydrogen density of 0.08375 kg/m³?

That value approximates hydrogen density at 1 atm and 15 °C. If your site uses different conditions, scale the release volume accordingly before entering it here.

How should I pick the allowable concentration?

Safety codes often treat 25% of the 4% LFL (i.e., 1% hydrogen) as an alarm threshold. Use a stricter value if your risk assessment demands more conservative dilution.

Does the calculator replace CFD modeling?

No. It offers a quick check on ventilation magnitude. Final designs should be validated with dispersion modelling, gas detection placement, and code compliance reviews.

Additional Information

  • Result unit: ventilation flow in cubic metres per minute and CFM plus air-change context.
  • Allowable concentration defaults to 1% by volume, staying below one-quarter of the lower flammability limit.
  • Purge time defaults to 5 minutes when not provided to align with common design guidelines.

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