104 – Hydrogen safety

HICKAM AIR FORCE BASE, Hawaii – Matt Morse, Project Engineer, demonstrates the use of the hydrogen station here May 13 on a one-of-a-kind, custom-built electric flightline maintenance support vehicle. The state of Hawaii formed a partnership with the Air Force and established the National Demonstration Center for Alternative Fuel Vehicles in 2001. Early projects included both hybrid and all-electric vehicles, to include the electric shuttle bus operating at the passenger terminal. More recently, a lithium battery-powered step van was developed and demonstrated and will soon go commercial. (U.S. Air Force photo by Senior Airman Carolyn Viss)

Contrary to popular belief, modern hydrogen storage systems are extremely safe. They are approved under the relevant standard:

  • CSA/UL for Canadian and American home and industrial hydrogen systems e.g. electrolyzers, storage tanks, stationary fuel cells etc.
  • DOT-SP for portable carbon fiber hydrogen pressure tanks used in zero emission vehicles

Most of the precautions needed to ensure hydrogen safety are nearly identical to other flammable fuels:

  • Only use CSA/UL/DOT approved fuel tanks, valves and electrical equipment.
  • Do not smoke or use any flame source within 5 meters of any hydrogen fuel.
  • Do not bring any oxidizing agent (e.g. medical oxygen) within 5 meters of any hydrogen fuel.
  • Fuel tanks should be placed well away from combustible (e.g. wood) buildings and other fuel sources.
  • Do not subject any fuel tank or related equipment to:
    • mechanical damage (e.g. drops or impacts)
    • fires
    • misuse
  • Keep hydrogen equipment in good repair. Inspect valves and tanks regularly for signs of damage.

The added risks that are different with hydrogen versus fossil fuels (diesel, propane etc.) are:

  • Pressurized storage is required. High pressure leaks are possible, but all modern carbon fiber pressure tanks are designed to leak before bursting.
  • Hydrogen is flammable at a lower concentration than propane, meaning indoor applications for hydrogen require significant ventilation to be mandatory in all buildings.
  • Metal embrittlement means that special liners must be designed for hydrogen tanks; steel propane tanks cannot be used to store pure hydrogen.

In addition, there are several safety risks with fossil fuels that are not present with hydrogen:

  • Carbon monoxide poisoning
  • Increased risk of cancer and birth defects due to exposure to benzene
  • Particulate matter (soot) and nitrous oxides impacting respiratory health, especially from diesel engines
  • Hydrogen is much lighter than air, so outdoor leaks quickly evaporate and do not linger

Flammability:

Hydrogen is a flammable gas that can cause a fire at concentrations as low as 4%. This is lower than propane, meaning that a hydrogen leak inside an enclosed building is more dangerous than a propane leak. Hydrogen is also extremely light and will collect in roof and attic spaces quickly.

If you are planning on bringing hydrogen tanks indoors, ensure that the building is extremely well ventilated and the outlet for this ventilation is at the very peak of the building (otherwise, you will have “dead air spaces” where the extremely lightweight hydrogen can easily collect). Consult your local building, plumbing, gas and electrical codes and local inspectors for more details.

Hydrogen ventilation is already covered in Canadian and US Electrical codes, since lead-acid batteries (like those used in many home solar PV power systems) produce hydrogen when charging. There are standard formulas that homeowners and contractors can consult to size and position their vents appropriately. The formulas may not be appropriate for a large release of hydrogen inside a building, however, since they were not designed to work with hydrogen stored in tanks, only batteries which produce but do not store hydrogen.

We also help distribute larger outdoor electrolyzers which are fully CSA approved and will not require engineering approval. Please contact us for more details.

Transport of hydrogen:

Transport Canada regulates the safe transport of flammable fluids via land, sea or air.  Please refer to their Dangerous Goods program to learn how to legally transport hydrogen.  The rules are different whether you are transporting for personal use or for commercial use. If outside Canada, contact the relevant authority.