HGD-2000 Hydrogen Gas Detector

Model # HGD-2000

The Eagle Eye HGD-2000 Hydrogen Gas Detector allows the user to monitor hydrogen gas buildup in storage rooms and facilities that house batteries - including forklifts, golf carts, backup power supplies, and battery charging stations. Lead-acid batteries on charge emit hydrogen gas after reaching the 80% recharge point. When mixed with enough air, hydrogen becomes a highly flammable gas that can ignite easily with just a spark, destroying equipment and harming personnel. The lower explosive level (LEL) for hydrogen is 4.1% by volume. The dangers of hydrogen gas explosion are eliminated by using the HGD-2000 hydrogen (H2) gas detector.

The HGD-2000 fixed hydrogen gas detector is easy-to-use and easy-to-install. Attach the HGD-2000 to the wall, ceiling, or optional junction box using the mounting holes at the top and bottom of the detector box. The detector has a terminal block for connection to single-phase AC power source and two internal relays. The relays can be used to switch a remote exhaust fan and/or alarm on and off. The detector should be kept on at all times, and the green LED will be lit. If the concentration of hydrogen gas in the air surrounding the sensor reaches 1% by volume, the yellow LED will light and the 1% internal relay will close. A four second delay prevents false activation. If the concentration reaches 2%, the red LED will flash, the internal 80 db warning alarm will sound, and the 2% internal relay will close.

The HGD-2000 Includes:

  • HGD-2000 Unit - AC Standard (Custom Option for DC-Powered)
  • User Manual

Hydrogen is colorless and odorless, the lightest of all gases and thus rises. The HGD-2000 should be installed at the highest, draft-free location of the room where hydrogen gas would accumulate. The sensor of the HGD-2000 consists of a semiconductor whose electrical conductivity increases when hydrogen is absorbed on its surface. Conductivity, proportional to the gas concentration, is continuously measured by an electric circuit. The HGD-2000 is factory-calibrated and field-calibrations should not be performed.

Properly installed, the HGD-2000 is compliant with The National Electric Code (NEC) Section 480.9 (A) for ventilation of battery rooms. This is also the specified requirement for solar or wind generated power Battery Rooms. The hydrogen gas detector is also compliant with The National Fire Protection Association, NFPA 2 Hydrogen Technology Code, which is more stringent. The minimum system consists of an H2 Hydrogen Gas Detector, an H2 Battery Room Forced Ventilator with Positive Airflow Shut Off, a remote firefighter’s shutdown capability, a backflow damper, and a 2% monitored alarm. This unit complies with NEC 501.125. (B), 501.105 (1)-3 and is designed for use in Class 1 Div. 2 Group B hydrogen containing classified areas.

Optional accessories for the HGD-2000 hydrogen gas detector include a steel junction box for hard-wiring to the wall or ceiling, a remote box for placement at eye level or in another room, and a telephone-type modular cable for connecting the remote box to the HGD-2000 detector. If you are testing other combustible gases such as propane or methane see our GD-3000 Combustible Gas Detector to meet your needs.

  • Technical Specs
  • FAQs
  • Advantages
  • Applications

Technical Specs

Alarm Relay:Form A, Normally-Open standard
Form B, Normally-Closed upon request
Form C, available at additional cost
Mounting:(4) 4.5 mm (3/16 in) screws
Operating Environment:-10 – 40 °C (14 – 104 °F)
Power Requirements:85 – 265 VAC, 50/60 Hz (standard)
17 – 60 VDC (upon request)
Dimensions:178 x 120 x 55 mm (7 x 4.75 x 2.5 in)
Safety Standard:IEEE Standard 450; National Protection Agency (NFPA) Article 64; NFPA 2: Hydrogen Technologies Code; Uniform Building Code (UBC) Section 6400; National Electric Code (NEC) Section 480.9 (A); NEC 501.125 (B); NEC 501.105 (1)-3 - use in Class 1 Division 2 Group B.


What regulations apply to battery charging areas?
OSHA Regulations (Standards - 29 CFR), National Electrical Code (National Fire Protection Association Standard NFPA 70), and associated directives, interpretations and compliance letters apply. For the latest information, see the web sites of OSHA (osha.gov) and NFPA (nfpa.org). Other regulations, state and local, may also apply.

What do these regulations require?
To the best of our knowledge at the time of this posting, existing regulations require that:

  • a. Provisions be made for sufficient diffusion and ventilation of gases from storage batteries to prevent the accumulation of explosive mixtures.
  • b. Adequate ventilation means providing natural or mechanical dilution sufficient to limit the accumulation of hydrogen gas in air at the charging site to levels below the lower explosive limit of 4.1%.
  • c. A typical exhaust fan can meet this requirement if it is used in such manner that the concentration of hydrogen gas in the fan's ambient air never exceeds the lower explosive limit.

What can cause a hydrogen gas explosion?
Hydrogen gas, 4.1% or more mixed with air, can be ignited by a flame, spark, or static electricity.

Can the detector itself cause an explosion?
Not if you make tight wire connections to the detector. The only moving parts are in the internal relays, and the relays are hermetically sealed.

Can you see or smell hydrogen?
Hydrogen is a colorless, odorless gas. Human senses cannot detect it.

What causes the odor in a battery room?
The odor in a battery room often is caused by a small amount of sulfuric acid vapor escaping into the air during finish charge. It is not caused by hydrogen, which is odorless.

When is hydrogen produced during battery charging?
When lead acid batteries, on charge, reach approximately 2.38 volts per cell ( 80 % of their full charge capacity ), they begin to gas. At that point, electrical energy in excess of what is needed for the chemical reaction, decomposes the water of the electrolyte into oxygen at the positive plates and hydrogen at the negative plates. Even after the charger turns off, the cells continue to produce oxygen and hydrogen until the reaction in the battery stabilizes. Fully charged, lead acid batteries on float charge continually emit oxygen and hydrogen, although at a lower rate than batteries being recharged.

How much hydrogen do flooded batteries emit?
The amount of hydrogen gas emitted during gassing depends upon the: a. Charger output current. b. Number of cells. c. Condition of the battery.

Where does hydrogen gas accumulate?
Hydrogen exits flooded batteries through the vent plugs. The concentration at the vent plugs is very explosive. As it exits, it dissipates in the air and, being the lightest of all gasses, rises. It can accumulate again in explosive concentrations in the highest, draft- free areas of the room. The main purpose of the hydrogen detector is to prevent this.

Do VRLA (sealed) lead-acid batteries emit hydrogen?
VRLA (valve regulated lead acid) sealed batteries use a recombination technique to prevent water loss in the form of oxygen and hydrogen gas. They often require special chargers with specific charge profiles for the brand and type of battery. Although VRLA batteries normally do not emit gases, they can do so under certain circumstances. They have pressure relief valves to control their internal pressure. If the pressure builds too high due to high ambient temperature, overcharge, mechanical failure or other causes, they can emit hydrogen gas in explosive concentrations. The potential danger is greatest with stationary VRLA batteries kept in small enclosures with limited ventilation.

Will the detector work in a non-oxygen environment?
No. The sensor requires an oxygen environment.

Does the detector detect or react to other gasses?
The sensor detects several other combustible gases in addition to hydrogen -- ethanol, isobutane, methane, propane. Its sensitivity to these other gasses, however, is much lower than its sensitivity to hydrogen. This should not noticeably affect its operation.

What is the detector operating temperature?
The detector operating temperature is 14 to 104 degrees F, ( -10 to 40 degrees C).

What is the response time?
When power is first applied, or after a power interruption, approximately 10 minutes will elapse before the detector starts to function. This delay is to prevent false activation. After this delay, response time to hydrogen for the first (1%) relay is about 4 seconds; response time for the second (2%) relay and/or alarm is 3 seconds later (total: about 7 seconds).

Does the detector have a built-in warning alarm?
The detector has a built-in 80 db warning alarm that activates at a 2% concentration of hydrogen.

Where should I place the hydrogen gas detector?
Install the detector at the highest, draft-free location in the battery compartment or room where hydrogen gas might accumulate.

How do I install the detector?
The detector is designed to attach directly to a wall or ceiling, or to a conduit box, using four screws. You will need to run power and relay wires to the detector, plus a modular cable to the optional remote, if used.

How is the detector powered?
Normal power is 115 volts 50/60 hertz ac. If specified at time of order, the detector can be customized for 220 volts 50/60 hertz ac, or for 12, 24, 36 or 48 volts dc.

How much power does the detector consume?
The detector consumes 80 ma, 170 ma if the buzzer is sounding.

How large an exhaust fan can the detector control?
The internal relay dry-contacts are rated at 10 amps / 250 vac, sufficient for most 1/3 HP fans. For higher current requirements, add an external relay.

How many detectors do I need?
Similar to smoke detectors, hydrogen detectors sense hydrogen only at the sensor, not at a distance. How many detectors you need depends upon where hydrogen might accumulate near your ceiling. Factors affecting this are: a. Room size. b. Type of ceiling -- flat, pitched, compartmented, etc. c. Natural air flow patterns. If unsure, add one or more detectors to be safe.

Can one detector control more than one sensor?
No. The detector can operate only one sensor.

Can the sensor be remotely mounted from the detector?
Normally, no. The sensor is mounted on a small board inside the detector. For special OEM requirements, some modifications can be made. Consult Eagle Eye.

How can I be sure the detector is working?
Each detector has a test button. Push and hold the test button for ten seconds. The LED’s will light in sequence, the relay(s) will close to operate whatever is connected, and the warning buzzer will sound. This test can also be run from the optional remote, if used. This procedure will test the detector’s electronics, but not the sensor itself. There is no way accurately to test the sensor in the field. If you have hydrogen in a tank, you can fill a balloon with hydrogen and release it at the sensor to see the reaction. Do not use hydrogen sulfide - it can damage the sensor. For a more accurate test, you can purchase test gas from a gas supplier and flood the sensor with it, but these concentrations are very small and may not give a correct result. Fortunately, when the sensor fails, often due to contamination, it normally becomes more sensitive, falsely activating the relay and/or alarm.

How long will the sensor last?
Normal sensor life is over 5 years. For safety sake we suggest you replace it every 5 years.

How can I replace the sensor?
To replace the sensor, order a new sensor board from your dealer or Eagle Eye. Remove the cover of the detector. Pull out the old sensor board and insert the new board. Replace the cover. Run the push-to-test-button procedure. That’s all there is to it.

What is the warranty?
Hydrogen gas detectors are warranted to be free of defects in workmanship and material for a period of two years from the date of purchase.

Where can I buy an Eagle Eye HGD-2000?
You can buy a detector directly from Eagle Eye Power Solutions, LLC.

What is the recommended wiring gauge for installing the HGD-2000?
You should consult your electrician or an engineer for the proper wire gauge for your application. You will want a wire gauge that is sufficient for carrying the appropriate load from your circuit breaker which may vary in size based on 120/220 VAC and your specific application.


  • Compliance with IEEE Std 450
  • Compliance with National Fire Protection Agency (NFPA) Article 64
  • Compliance with Uniform Building Code (UBC) Section 6400
  • Automatic Operation and Continuous 24/7 Monitoring
  • High Sensitivity and Stability
  • Long Life-Span for Reliable Monitoring
  • 12V DC Operation Voltage
  • Inexpensive protection for equipment and personnel
  • Save electricity, heating, and air conditioning costs by not continuously running exhaust fans
  • Save insurance costs - reduce insurance premiums when placed in battery charging rooms
  • Two-Year Warranty


  • Utilities and Power Plants
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  • Nuclear Waste Reforming
  • Hydrogen Refueling Stations
  • Fire Department
  • Battery Suppliers
  • Battery Charging Rooms
  • Motive Power
  • Golf Cart
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    Fixed Hydrogen (H2) Gas Detector

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How To: Replace a HGD-2000 Sensor Board

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