Installing a Lab Hydrogen Generator Safely: ATEX, NFPA 2 & ISO 22734 Codes
By Raymond Xie, Hovogen R&D Division Director · Last updated 17 September 2026
How this guide was prepared: the installation, operating and alarm parameters below are taken from the Hovogen LH Scientific Hydrogen Generator (LH-LX) user's manual (Ver 1.5, 2026-03) and field commissioning practice; the regulatory content is sourced directly from the primary standards cited at the end of this article.
A bench-top PEM hydrogen generator is one of the safest ways to supply hydrogen to a GC-FID, GC-MS or ICP-MS. It also concentrates a flammable gas, at pressure, inside a room where people work. The difference between a compliant installation and a risky one is rarely the machine itself — it is how the room, the utilities and the documentation around it are prepared.
This guide maps the three standards that govern the job — ISO 22734, NFPA 2 and the EU ATEX directives — to the practical steps a lab manager or safety officer must complete before, during and after installation. It reflects the parameters of a real, current-generation instrument: a PEM water-electrolysis generator rated at 4000 mL/min, 99.99% purity, up to 16 bar outlet pressure and ≤1500 W (LH-LX series, Ver 1.5).
Why hydrogen is different from other lab gases
Hydrogen's hazard profile is unusual — a fuller treatment of its safety characteristics is on our blog — and it drives nearly every requirement below.
Lower flammability limit (LFL): 4% in air · small leaks can create a flammable atmosphere in an enclosed room
Upper flammability limit (UFL): 75% in air · flammable over an exceptionally wide range
Minimum ignition energy: ≈0.017 mJ · lower than almost any other fuel gas — sparks, static and hot surfaces can ignite it
Auto-ignition temperature: ≈500–585 °C · hot surfaces and some heater elements can ignite it
Density: ≈0.09 kg/m³ (≈1/14 of air) · it rises and accumulates at the ceiling; leaks disperse quickly outdoors but pool under ceilings indoors
Flame: nearly invisible · leaks can burn undetected; use a thermal or UV detector, not the eye
The practical consequence: installation is governed by preventing accumulation (ventilation and detection) and eliminating ignition sources (electrical area classification). Everything in ISO 22734, NFPA 2 and ATEX exists to force those two outcomes.
The three standards at a glance
They are not competitors — they act at different layers.
ISO 22734-1:2025: product / manufacturer layer · applies to hydrogen generators using water electrolysis · construction, safety and performance requirements — the certificate you should demand from the supplier
NFPA 2 (2023), Hydrogen Technologies Code: installation and use layer (North America) · ventilation rates, separation distances, electrical area classification, venting of generators
ATEX 2014/34/EU + 1999/92/EC: equipment + workplace layer (EU/UK) · zone classification, Explosion Protection Document, category-rated equipment
Supporting references: IEC 60079-10-1 (area classification), ISO 14687 (purity grades), ISO 19880-1 (fueling)
ISO 22734 — the product standard. ISO 22734 defines the safety and performance requirements for hydrogen generators that electrolyse water, including PEM, alkaline and AEM types. The 2019 edition (ISO 22734:2019) was withdrawn and replaced by ISO 22734-1:2025 (“Hydrogen generators using water electrolysis — Part 1: Safety,” published July 2025, ISO/TC 197). When you procure a generator in 2026, ask the supplier for a certificate of conformity to ISO 22734-1:2025, not just a generic CE declaration. This is the document that proves the machine's own safety design — pressure limits, leak containment, alarms and shut-down logic — has been assessed.
NFPA 2 — the installation and use standard. NFPA 2, the Hydrogen Technologies Code, is the reference for how a hydrogen system is installed in a building. Two requirements shape lab installations:
Ventilation: mechanical or fixed natural ventilation shall be provided at a rate of not less than 1 scf/min per ft² (0.0051 m³/s per m²) of floor area over the area of storage or use. In practice, labs target a concentration of 1% vol (25% of the LFL) as the design ceiling for any credible release — a dilution-based approach echoed by ISO 22734 and IEC 60079-10-1
Electrical area classification: NFPA 2 classifies areas as Class I, Division 1 or 2, Group B (hydrogen), by analogy with the EU zone system, and points to NFPA 70 (NEC Article 500) and IEC 60079-10 for the method
ATEX — the EU equipment and workplace rules. “ATEX” is two directives, and confusing them is the most common compliance error:
Directive 2014/34/EU (equipment): applies to manufacturers · equipment for potentially explosive atmospheres is grouped as Category 1G / 2G / 3G for gas · Category 1G suits Zones 0, 1 and 2; Category 3G suits Zone 2 only
Directive 1999/92/EC (workplace): applies to you, the employer · classify areas into zones, prepare an Explosion Protection Document (EPD), select equipment suitable for each zone, and train workers
Hydrogen sits in the highest-risk gas group IIC, and is normally assigned temperature class T1 (maximum surface temperature 450 °C). Any Ex-rated device installed near a hydrogen source must carry an appropriate IIC/T1 marking.
Step 1 — Pre-installation preparation
Site and room assessment
Choose a stable, ventilated location. The generator must be fixed in a stable, ventilated position and kept away from fire. A bench that can be knocked over is not acceptable; the unit is heavy (≈33 kg) and must be placed horizontally on a level surface.
Verify ventilation sufficiency against the NFPA 2 area-based rate, and confirm whether the room's air changes are adequate for a credible release. If the space is shared or poorly ventilated, plan mechanical extraction or duct the generator's vent to a safe location.
Position the gas path deliberately. Vent and relief points should discharge away from air inlets, ignition sources and occupied zones. Where possible, pipe purge vents to an extraction system or outdoors rather than into the room.
Confirm the ceiling volume. Because hydrogen accumulates at high level, ceiling height and high-level ventilation — not only floor-level extraction — determine real safety.
Environmental and utility verification
Ambient temperature: 5–50 °C · avoid hot spots; fan-cooled units lose cooling capacity at high ambient temperature
Ambient humidity: ≤90% RH · condensation risks electronics
Power supply: 220 V / 50 Hz (customisable), ≤1500 W · dedicated, earthed circuit; verify voltage stability
Water quality: ≤1 µS/cm (deionised / TDS ≤1) · poor water triggers alarms and degrades cell performance
External water tank: ≥1.5–2 L pure water, internal tank 2.5 L · auto-refill pump requires a secure, level supply
Footprint / weight: 450 × 445 × 350 mm / 33 kg · two-person lift; level, load-rated bench
Water quality is a safety control, not just a consumable. Conductivity above the limit causes the electrolyser to degrade and, over time, to overheat — and it measurably raises energy consumption in PEM water electrolysis. The generator's in-service water-quality alarm is set to 5 µS/cm, with an over-temperature alarm at 60 °C.
Documentation and classification review
Before the unit is switched on, assemble:
Certificate of conformity to ISO 22734-1:2025 (or the applicable edition) and the CE/UKCA declaration
Ex marking for any electrical equipment installed in a classified area (group IIC, temperature class)
Risk assessment and, where ATEX applies, the Explosion Protection Document and the site's zone drawing
The equipment user's manual, the installation record, and the supplier's maintenance schedule
Step 2 — Safety specifications during installation and operation
Ventilation and gas detection
Size ventilation to the area-based NFPA 2 rate (0.0051 m³/s per m²) and, where a release is plausible, to dilute it below 1% vol. Install hydrogen detection calibrated to alarm at a fraction of the LFL — 1% vol is the conventional setpoint, well below the 4% LFL — with visual and audible alarms wired to shut the generator down if extraction fails.
Pressure management
The generator's pressure boundary must be protected at every level:
System and outlet pressure are limited to 1.6 MPa (16 bar); the system does not permit operation above this, and the default production stop pressure is 1.6 MPa
The hydrogen outlet pressure alarm and system pressure alarm must be set at or below the downstream vessel's rated pressure, so an over-pressure condition stops the machine before it stresses the receiver. As a working rule: if you operate at 1.0 MPa, set the outlet and system pressure alarms to 1.5 MPa — the alarm band sits above working pressure but below the vessel limit
A pressure-relief device must vent to a safe location, never into an occupied space
Factory alarm setpoints (LH-LX class)
Water tank over-temperature: 60 °C · radiator cooling engages; investigate airflow and ambient temperature if recurrent
Circulating water quality: 5 µS/cm (recommended ≤5) · replace with deionised water ≤1 µS/cm; sustained high conductivity degrades the cell
Circulating water flow: speed-dependent · too fast reduces electrolysis efficiency; too slow causes poor heat dissipation — restore rated flow
H₂ outlet / system pressure: upper limit ≤1.6 MPa · verify vessel rating and alarm margin; never operate above the vessel's design pressure
Ignition-source control
Keep the unit away from all ignition sources — open flame, hot work, and unrated electrical equipment
In a classified area, only Ex-rated (IIC/T1 or better) equipment may be used; bonding and earthing must be continuous
Avoid static-generating materials and ensure metal components are bonded
Operational rules that prevent incidents
These come from the equipment manual and apply to every operator:
Never unplug the oxygen outlet while the generator is producing hydrogen — oxygen is co-produced and vented through that port
On disconnect, the hydrogen line is pressurised. Stand clear, never point the outlet at a person, and keep it away from fire; a loud release is normal
Drain the water tank if the unit will be idle for a long period — connect the drain line and let gravity empty it
Do not modify protected parameters such as the electrolytic cell layer count or the maximum flow beyond the model's rated range
Step 3 — Operating the control interface
The LH-LX runs on a resistive touch screen with two layers you will use daily. Knowing what each screen does — and what it must not be used for — is part of safe operation. (A fuller walkthrough is available in our LH-LX review and performance analysis.)
Production dashboard. The Flow Setting (mL) field sets the output rate — 4000 mL/min on this unit; do not exceed the model's rated maximum. START begins production: the filling pump runs to the designed liquid level, the circulation pump starts, and electrolysis begins. STOP disconnects the electrolysis power supply and shuts pumps and fans down in sequence. Three tiles matter most for safety oversight:
Operation Monitoring: real-time liquid level, water quality, water temperature, circulating-pump flow, electrolyser voltage and current feedback, system pressure and outlet pressure · read it during commissioning; it is the screen to watch during the two-person pressure adjustment below
Parameter Setting: password-protected · alarm setpoints live here; apart from flow and the pressure alarm band, leave factory values unchanged
Alarm Query: the first screen to open whenever the buzzer sounds · it names the fault (water quality, temperature, flow or pressure) so you can act on the cause rather than silence the symptom · Historical Data complements it with the machine's logged operating parameters
Manual Control panel. Individual toggles for the circulating water pump, filling pump, oxygen cooling (heat exchanger), exhaust fan, buzzer and electrolysis power supply, plus a Manual/Automatic selector. Manual mode exists for commissioning and service only — the classic case is first fill: switch to Manual, run the filling pump until the water level reaches the upper limit, then switch back to Automatic. Normal production belongs in Automatic mode, where the system enforces its own limits.
Five interface rules that prevent incidents:
Automatic is the operating mode; Manual is a maintenance mode. Never leave the machine unattended in Manual.
Two-person pressure adjustment. One person adjusts the pressure switch (clockwise to raise, counter-clockwise to lower) while the other watches system pressure on Operation Monitoring; wait until the reading holds steady for 5 minutes.
Respond to alarms through Alarm Query, not by muting the buzzer.
Treat the screen as an indicator, not a control surface — Operation Monitoring values are read-only by design.
If the display does not respond at power-on, wait for the interface to load before tapping; early tapping enters the remote-debug (Wi-Fi) screen.
Step 4 — Compliance checklist
Before commissioning
1. Room ventilation meets NFPA 2 area rate / dilution target: evidence — commissioning airflow measurement
2. Area classified (ATEX zone / Class I Div) and EPD in place: evidence — zone drawing + EPD
3. Only Ex-rated, IIC/T1 equipment in classified areas: evidence — Ex certificates
4. Gas detection installed and tested (1% vol alarm): evidence — sensor calibration record
5. Pressure relief vents to a safe location: evidence — installation drawing
6. Water quality ≤1 µS/cm verified: evidence — conductivity reading
7. Power circuit dedicated, earthed, ≤1500 W: evidence — electrical certificate
8. ISO 22734-1 conformity + CE/UKCA on file: evidence — manufacturer documents
Ongoing compliance
Train and re-train operators on ATEX duties, alarm response and shut-down
Log alarms (water quality, temperature, pressure) and act on trends, not just trips — recurring water-quality trips usually mean the deioniser, not the machine
Inspect seals, tubing, relief devices and detection sensors on a fixed schedule; plan for the maintenance profile over 10,000+ operating hours
Keep records: commissioning data, maintenance, training and any incident — these are the evidence base for your EPD and any audit
FAQ
Does a lab hydrogen generator need ATEX certification?
Not necessarily as a product, but the installation must be assessed. Under ATEX 1999/92/EC the employer classifies zones and documents them in an EPD. A sealed, low-pressure generator may not require a classified zone, but the outlet, relief and any credible leak source must still be evaluated. Higher-pressure units (up to 16 bar) warrant a formal assessment around their release points.
What ventilation rate does NFPA 2 require?
NFPA 2 (2023) requires mechanical or fixed natural ventilation of not less than 0.0051 m³/s per m² (1 scf/min per ft²) of floor area over the area of storage or use. Many labs also design to dilute a credible release to 1% vol (25% of the LFL).
Which ISO 22734 edition applies in 2026?
ISO 22734-1:2025, published July 2025, which replaced ISO 22734:2019. Request conformity to the current edition.
What water quality does a PEM generator require?
Deionised water with conductivity ≤1 µS/cm. Above this, in-service alarms trigger at 5 µS/cm and long-term performance degrades.
What is Manual Control mode for?
It is a commissioning and service mode that lets you run individual components (filling pump, circulation pump, exhaust fan, electrolysis power) outside the automatic programme — typically for the first water fill. Normal production should always run in Automatic mode, where the system enforces pressure, level and water-quality limits on its own.
What zone is a typical lab hydrogen generator?
With good ventilation and a sealed system, the immediate vicinity is often Zone 2 or unclassified, with Zone 1 reserved for release points. The classification is site-specific and must be documented.
Standards and sources
Primary references used in this guide:
ISO 22734-1:2025, Hydrogen generators using water electrolysis — Part 1: Safety (ISO/TC 197, published July 2025) — iso.org/standard/82766.html
ISO 22734:2019 (withdrawn; replaced by ISO 22734-1:2025) — construction, safety and performance requirements
NFPA 2, Hydrogen Technologies Code (2023 edition) — nfpa.org/product/nfpa-2-code/p0002code
Directive 2014/34/EU (ATEX equipment) — eur-lex.europa.eu/eli/dir/2014/34/oj
Directive 1999/92/EC (ATEX workplace) — eur-lex.europa.eu/eli/dir/1999/92/oj
Hovogen LH Scientific Hydrogen Generator (LH-LX) User's Manual, Ver 1.5, 2026-03
Supporting: IEC 60079-10-1 (area classification), ISO 14687 (hydrogen fuel quality), ISO 19880-1 (gaseous hydrogen fueling)
The bottom line
Compliance is a documentation and room-design problem more than a machine problem. Buy a generator certified to ISO 22734-1:2025, install it to NFPA 2 ventilation and area-classification rules, and run it under a documented ATEX regime. Get those three layers right and a bench-top PEM generator is one of the safest hydrogen sources available to a laboratory — and, on a 3-year total-cost basis, usually the cheapest.
More answers are on our hydrogen FAQ; for installation support and compliance documentation, contact our applications team.
Author
Raymond Xie, Hovogen R&D Division Director
Raymond Xie leads the R&D Division at Hovogen, developer of PEM hydrogen generation systems for analytical laboratories and industrial applications.
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