Safety engineering notes

Ammonia Safety: The Reference Detail

The background behind H2ONE's safety architecture: the hazard, the exposure limits, the standards we design against and the handling practice we follow.

Ammonia is hazardous and requires specialised storage, handling and operating controls. H2ONE's vehicle fuel system remains under engineering development and validation. Listing a standard does not mean the system is certified.

Know the hazard

Ammonia is toxic. It is also one of the world's most widely handled industrial chemicals.

Global industry has decades of codified practice for storing, transporting and using ammonia. H2ONE's job is to apply that discipline to a small, controlled mobility system, not to reinvent it.

−33 °CBoiling point. Stored as a liquid under moderate pressure (≈8.6 bar at 20 °C).Reference

≈0.6 × airDensity of warm NH₃ gas. A pressurised liquid release can instead form a cold, dense aerosol cloud that stays near the ground at first.Reference

<5 ppmOdour threshold. A strong warning smell far below harmful levels.Reference

≈16–27 %Flammable range in air. Narrow and hard to ignite compared with most fuels.Reference

Toxic & corrosiveThe main risks are inhalation and contact with eyes and skin.Reference

Exposure limits

Where the numbers sit, and where our alarms sit.

Ammonia in air, ppm (log scale) Reference Target · alarm set-points

1101001000

5 ppmOdour threshold

25 ppmREL / TLV · TWA

35 ppmSTEL · 15 min

50 ppmOSHA PEL

300 ppmIDLH

H2ONE warning set-point · 20 ppmH2ONE shutdown set-point · 30 ppmDesign targets

Occupational limits: NIOSH REL 25 ppm (10-h TWA) and 35 ppm (15-min STEL); ACGIH TLV 25 / 35 ppm; OSHA PEL 50 ppm (8-h TWA); NIOSH IDLH 300 ppm. H2ONE's warning and shutdown set-points are design targets, placed at or below the occupational limits.

Standards & guidelines

The rulebook we design against.

India

Reference

IS 4544: Ammonia, Code of Safety (BIS)Properties, hazards, storage, handling, PPE and first aid.
Gas Cylinders Rules, 2016 (PESO)Filling, possession and transport of gas cylinders, including vehicle-size vessels.
SMPV (Unfired) Rules, 2016 (PESO)Licensing of larger static and mobile pressure vessels, such as depot storage.
MSIHC Rules, 1989Hazardous-chemical storage, on-site emergency plans and notification above threshold quantities.
Factories Act, 1948 · Schedule IIPermissible workplace exposure levels.
CMVR type approval (ARAI / ICAT)Vehicle approval pathway for a new fuel system, to be defined with the regulators.

International

Reference

OSHA 29 CFR 1910.111Storage and handling of anhydrous ammonia, including excess-flow protection on vessel openings.
CGA G-2.1 / ANSI K61.1Safety requirements for anhydrous ammonia storage and handling.
NIOSH / ACGIH exposure limitsREL and TLV 25 ppm TWA, 35 ppm STEL; IDLH 300 ppm.
IMO MSC.1/Circ.1687 (2024)Interim guidelines for ships using ammonia as fuel, relevant to our future marine applications.

These are the reference frameworks H2ONE designs against. Listing them does not mean the vehicle system is certified. Approvals for an ammonia-fuelled vehicle will be pursued with PESO and the vehicle-testing agencies as the programme matures.

Handling practice

How we handle ammonia, day to day.

ReferenceCompatible materials onlySteel and stainless steel in the fuel path. No copper, brass, bronze, zinc or galvanised parts, which ammonia attacks.

ReferenceExcess-flow & reliefExcess-flow protection on vessel openings; pressure relief routed to a vent or scrubber, never into the cabin.

TargetDetection where the gas goesDetector positions set from release and dispersion analysis, not from buoyancy assumptions; warning and shutdown thresholds at or below occupational limits.

TargetClosed-connection refuellingTrained depot staff only. Sealed couplings, no open pouring or manual transfer, leak check before and after every fill.

ReferencePPE & first aidChemical goggles or face shield, ammonia-rated gloves and respirators; eyewash and safety shower at the depot.

ReferenceEmergency responseWater fog to knock down vapour, never a water jet onto liquid ammonia. Written plan, drills and an SDS on site.

TargetTraining & SOPsPermit-to-work, refuelling and maintenance SOPs, operator training and periodic drills.

TargetInspection & retestingRoutine leak checks, valve inspection and vessel retesting on the statutory schedule.

What investors ask

"Ammonia is toxic. How will you handle it?"

Why use a toxic fuel in a vehicle at all?

Ammonia carries hydrogen as an easily stored liquid, and India already produces, moves and handles it at industrial scale. The toxicity is real, so it is managed the way industry manages it: containment, detection, isolation and mitigation. It also has useful safety traits: a strong smell below 5 ppm (long before dangerous levels) and a narrow flammable range. Its vapour behaviour depends on release conditions: a pressurised liquid release can form a cold cloud that stays low at first, so H2ONE does not rely on buoyancy alone.

Where is the tank, and what protects the driver?

In the current packaging concept, the vessel and its valves sit in an isolated, negatively ventilated enclosure separated from the occupant space. A leak is drawn away from the occupants, treated or purged, and released through a controlled discharge directed away from cabin openings. NH₃ detection in the occupant space acts as a backstop. This is the same principle as the vapour-tight housings on LPG and CNG vehicles, applied to a toxic gas. The final location remains subject to crash, packaging, dispersion and regulatory validation.

What happens if a line breaks or the vehicle crashes?

The design target is for the excess-flow valve to close on a line rupture and the normally-closed valve to shut on any power loss. A crash or tilt switch also closes the in-tank valve. The vessel is small (10 kg target) and sits in a sealed, negatively ventilated enclosure. Crash behaviour is a validation item in the programme, not a completed test.

Who refuels the vehicles?

Only trained staff at a controlled depot, using closed-connection couplings. There is no public refuelling in the first deployments: 1 engineering vehicle, then a 5-vehicle pilot, then a 20-vehicle monitored fleet.

Which regulations apply, and are you certified?

Not yet. The vehicle fuel system is in development. We design against IS 4544, the PESO Gas Cylinders and SMPV(U) Rules, the MSIHC Rules and international references such as OSHA 1910.111 and CGA G-2.1. We plan to engage PESO and the vehicle-testing agencies early to define the approval pathway.

How will you prove it is safe?

Through staged testing, reported openly: component and leak tests, sensor and shutdown response, vibration and durability, then dyno and depot trials, with independent validation. Results are labelled experimental, simulated or target, and setbacks are reported early.

Sources