MOLARIS
Safety Distance Calculator
GH2: by pressure and actual pipe diameter (2023/2026) or typical table (2020). LH2: by volume (2020) or by pressure and actual diameter (2023/2026). Also includes distances for GH2 dispensing stations. The input mode adapts automatically to what you select.
This tool is an indicative reference aid prepared by MOLARIS based on our own interpretation of NFPA 2 technical criteria. It is not an official or NFPA-certified product, and it does not replace the code text or the analysis of a competent engineer. Values may contain transcription or interpretation errors, become outdated by subsequent amendments (TIAs), or not apply to your specific case. Always verify results against your current, up-to-date copy of NFPA 2 before using them in any design, report or safety decision. MOLARIS assumes no liability for decisions, designs or damages arising from the use of this tool, to the maximum extent permitted by law.
MOLARIS is not affiliated with, sponsored by, or authorized by the National Fire Protection Association (NFPA). "NFPA" and "NFPA 2" are trademarks of their respective owners, cited here solely for identifying technical reference purposes.
Distances marked as internal review have been cross-checked, at our own discretion and without external validation from NFPA, against three sources we consulted: NFPA 2-2020, NFPA 2-2023 and NFPA 2-2026. This is not an official verification or a certification of accuracy — it is our best reading of the text, subject to error and revision.
- Structural change: in 2020, LH2 bulk storage is organized by stored volume (gal); starting in 2023 it switched to being organized by pressure, like GH2, and that structure continues in 2026. The tool switches modes automatically based on the edition you select.
- GH2 non-bulk and LH2 non-bulk turned out to be identical across all three editions consulted.
- GH2 bulk (typical table) and LH2 bulk by actual diameter: the 2023 values match the 2026 values in our reading, although the table numbering changed from edition to edition. Exception: the GH2 actual-diameter formulas do change coefficients between 2023 and 2026.
- Accuracy by actual diameter: for GH2 and LH2 bulk in 2023/2026 we apply engineering formulas D = a·d + b (d = pipe inner diameter in mm) instead of the simplified "typical" diameter.
- Dispensing station (GH2): fixed separation distances for dispensing equipment and transfer points, per our reading of NFPA 2-2023.
01 Edition and physical state
Select the code edition and whether the system is compressed hydrogen gas (GH2) or liquid hydrogen (LH2).
02 Pressure / volume
Select edition, state and scale to continue.
03 Exposure to evaluate
Choose which type of exposure determines the distance you need.
04 Mitigation
NFPA 2 allows these distances to be reduced through firewalls ("passive means") or active control systems approved by the authority having jurisdiction ("active means"). This tool does not calculate that reduction: it is an engineering decision subject to detailed structural requirements (number of sides and wall angles, fire resistance, ventilation, design against deflagration/wind/seismic loads, among others) that you must verify directly in your official copy of NFPA 2 with a competent engineer.
▸ What does each exposure type mean? (quick glossary)
Exposure Groups 1/2/3: these are not an abstract "more to less dangerous" scale, but categories set by the code itself based on the type of expected consequence; each table defines which specific exposures fall into each group (that's why you'll see them listed in each card).
Lot lines: the legal boundary of the parcel that can be built on — not necessarily a physical fence, but the cadastral boundary.
Air intakes: HVAC air intakes, compressors or other equipment that draws in ambient air.
Operable / non-operable openings: windows, doors or vents that can be opened (operable) versus those that are fixed or sealed (non-operable) in a building or structure.
Firewall (passive means): under NFPA 2-2023, under strict structural conditions, allows the Group 1 and 2 distance for GH2 bulk to be reduced to 0 ft — it is not a percentage, it is a total reduction subject to compliance with all code requirements. Always verify the official text.
Combustible / non-combustible construction: refers to the structural materials of the exposed building (wood, for example, versus concrete or steel), not to the hydrogen system.