H2S Analyzer

Model: 331 Transportable H2S Analyzer

A transportable system that can measure H2S in natural gas anywhere you need it. This uniquely rugged and simple design by Envent utilizes a lead acetate-based sensoring system that provides a linear and interference free output of the H2S concentration.

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An analyzer that measures H2S and/or Total Sulfur (optional) in natural gas, petrochemical streams, condensate, or LPG with optional integrated CO2 IR bench.


  • Rugged, weatherproof Pelican® case with extension handle and wheels
  • Self-contained sample conditioning system
  • On-board data logging (no chart recorders required)
  • Ranges from 0–50 ppb to 0–100%
  • 1.5% accuracy, 1% repeatability
  • Modbus Serial communications,
  • Displays up to 5 times full scale
  • Dual Isolated 4–20 mA outputs
  • less than 20-second response time to alarm
  • Optional Total Sulfur and CO2
  • Interference-free Lead acetate sensor
  • 60–90 day tape (longest tape life in the market)
  • Zero sensor drift


The 331 measures H2S in natural gas or other process gases. The unit has dual 4–20 mA outputs, dual measurement alarms, plus trouble and fault alarm relays. The 331 displays H2S concentration in user-specified units (ppb, ppm, grams, %, m/g3) and as well will auto range to 5 times the lower calibrated range. Calibration is performed manually via the operator interface or automatically when connected to a calibration bottle and optional auto calibration solenoid. The 331 is available with a number of sample systems and accessories to handle various applications such as high range H2S, Total Sulfur or H2S in liquids.

Lead Acetate Sensors: Lead acetate is essentially interference-free from other sulfur compounds. This is why it is used by the vast majority of industry users when accurate measurement is required. The linear output enables the user to perform a single-point calibration.

Longest Tape Life: Envent tape is the strongest in the market, with the longest tape life by using a proprietary tape advance algorithm to make complete use of the 300-foot tape. The unit will accept up to a 350-foot roll.


Power 12–24 vdc @ less than 3 watts
100–240 VAC, 50/60Hz
Electrical classification Class 1, Div 2 Grps A, B, C, & D certified to CSA standards
Ambient Temperature 0-50 ˚C (std) consult factory for other requirements
Output Ranges H2S 0-50 ppb to 0–100 ppm are standard. for higher concentrations, consult factory.
Response time 20-sec alarm
Accuracy 1.5% of full scale
Inputs 24 bit A/D
Microprocessor-based sensor block
Low Tape Alarm
Remote calibrate, Stream switch, or Low pressure
Outputs Dual isolated 4–20 mA (loop power required)
Modbus serial RS-232 & RS-485
Four 5 amp SPDT alarm relays (high reading, high high reading, low tape, failure)
Four solid state solenoid drivers ( auto cal, total sulfur, stream switching, valve actuator)
Displays 2 x 16 character LCD with backlighting
Menu is scrolled by internal button
Dimensions 30” x 20” x 11”
Weight 45 lbs.
Sample Pressure 5–1500 psig
331 Transportable H2S Analyzer