Hydrogen Plus Other Alternative Fuels Risk Assessment Models (HyRAM+) is a software toolkit that integrates publicly available data and models relevant to assessing the safety in the use, delivery, and storage infrastructure of hydrogen and other alternative fuels (i.e., methane and propane). The HyRAM+ risk assessment calculations incorporate probabilities of equipment failures for different components for both compressed gaseous and liquefied fuels, and probabilistic models for the effect of heat flux and overpressure on people. HyRAM+ also incorporates experimentally-validated models of various aspects of release behavior and flame physics. The HyRAM+ toolkit can be used to support multiple types of analysis, including code and standards development, safety basis development, facility safety planning, and stakeholder engagement.

HyRAM+ was supported by the U.S. Department of Energy (DOE) Office of Energy Efficiency (EERE) Hydrogen and Fuel Cell Technologies Office (HFTO), the DOE EERE Vehicles Technologies Office (VTO), and the U.S. Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA).

The HyRAM+ software is available under an open source license.

Access the source code for HyRAM+ via GitHub

Download the most recent build of the Windows-only installer

Note: please completely uninstall any previous versions of HyRAM or HyRAM+ before installing.


  • Default data for gaseous and liquid hydrogen, gaseous and liquid methane (as a proxy for natural gas), and propane systems modifiable by users:
    • component leak frequencies
    • ignition probability
  • Models of physical effects for consequence modeling:
    • Unignited release behavior
      • Buoyant jet
      • Accumulation in enclosure
    • Ignited release behavior
      • Jet fire trajectory, temperature, and radiative heat flux
      • Overpressure within enclosures
      • Unconfined overpressure from the delayed ignition of a buoyant jet
  • Probabilistic models for human harm from thermal and overpressure hazards
  • Fast running: to accommodate rapid iteration
  • Calculates common risk metrics for user-defined systems
    • Risk contributions for individual leak scenarios
    • Frequency of cut sets

Given a user-defined system, risk analysts can use HyRAM+ to answer the following types of questions:

  • How would changes to system design affect overall risk/safety?
  • Which design is the safest?
  • What is the likelihood of a release from an installation?
  • How likely is it that a jet fire or deflagration would occur?
  • What is the heat flux from a jet flame associated with a specific release?
  • At what distance does the concentration reach a no-ignition threshold?



Journal Articles 

Technical Reports 

Conference Papers 

Brian Ehrhart
HyRAM+ Team Lead
(505) 284-4906

Ethan Hecht
Hydrogen Behavior Expert
(925) 294-3741