Monitor, analyze and record the concentration of gases.

The Vapex SENTINEL S5 is the newest generation from SENTINEL technology. The S5 has improved algorithms, the newest components, and an upgraded user interface but retains the proprietary core technology. As the original multi-gas analyzer, the SENTINEL delivers consistent and reliable gas measurement data to optimize all properties that affect wet scrubber efficiency and longevity.

The S5 continuously monitors, analyzes and records the concentration of the gases entering and exiting the wet scrubber. The S5 sends a signal to chemical pumps modulating the chemical flow to the scrubber. The proprietary algorithm keeps gas concentrations at the customer’s specified setpoint preventing over-dosing and wasting chemicals. The S5 can also monitor pH, ORP and pressure ­­— parameters that indicate scrubber efficiency.


  • Accommodates 2, 3 or 4 H2S or Cl2 sensors – Multiple Sensor Ranges
  • Additional inputs: pH, ORP, Pressure & Temperature
  • Auto sensor cleaning
  • Self-purging sensor
  • Response time ~ 60 seconds
  • UV-resistant, sunlight-visible, hi-resolution color touch screen
  • Weather-proof NEMA 4X Enclosure
  • Programmable interface
  • 1-year sensor life
  • Booster pump for vacuum systems
  • Proprietary chemical pump control algorithm
  • 2 GB Removable SD Card Data Logger
  • LAN/Ethernet connection — 2 USB ports
  • Auto-Draining moisture removal system
  • Pump Control signal
  • Controlled rate of gas flow to sensors


  • Up to 50% decrease in chemical usage
  • Up to 50% increase in scrubber efficiency
  • Reduction in scrubber maintenance
  • Used in 1, 2, 3 or 4 stage scrubber designs
  • Reduces emission of corrosive gases from scrubber
  • Connection to SCADA
  • Monitor scrubber efficiency
  • Provides records of gas emissions to the atmosphere
  • Increased sensor accuracy
  • Increased sensor life
  • Ease of installation
  • Low maintenance cost
  • Overall operational savings

(Municipal Water & Wastewater)

  • Single & multi-stage gas absorption scrubbers
  • Bio-scrubbers & Bio-Trickling Filters (as a monitor)
  • Activated Media scrubbers (as a monitor)


Specifications SENTINEL S5
Gases Hydrogen sulfide & Chlorine
Number of Sensors 2, 3, or 4
Sensor Type Hydrogen sulfide — Electrochemical
Chlorine — 3-Electrode Electrochemical
Range Hydrogen sulfide: 0-20 ppm, 0-50 ppm,
0-100 ppm, 0-200 ppm & 0-300 ppm
Chlorine: 0-5 ppm, 0-10 ppm & 0-20 ppm
Response Time ~ 60 seconds
Accuracy ± 2%
Resolution 0.1 ppm
Drift ~1% monthly signal loss
Calibration Monthly or as needed
Sensor Life 1 year average
Unit Dimensions 17” D × 27”D × 55”H
Unit Weight 85 lbs
Enclosure NEMA 4X Powder-coated
Stainless Steel, stand alone
Operating Temperature 0°F to 120°F
Power 115VAC, 60Hz, 5A
User Controls Color Touchscreen HMI
Data logging & Memory 2GB SD Card (90-days at 1 min intervals)