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Electrochemical Toxic Gas Sensor Technology

Substance-specific electrochemical sensors

  • Gas diffusing into sensor reacts at surface of the sensing electrode
  • Sensing electrode made to catalyze a specific reaction
  • Use of selective external filters further limits cross sensitivity
substance-specific electrochemical sensors

Three electrode electrochemical toxic sensor

Three electrode electrochemical toxic sensor

Major Components of Electrochemical H2S Sensor

Major Components of Electrochemical

Electrochemical CO Sensor Detection Mechanism

Carbon monoxide is oxidized at the sensing electrode:

CO + H2O CO2 + 2H+ + 2e-

The counter electrode acts to balance out the reaction at the sensing electrode by reducing oxygen present in the air to water:

1/2O2 + 2H+ + 2e- H2O

And the overall reaction is: CO + ½O2 CO2

4CF Signal Output: 0.07 μ A / ppm CO

Electrochemical H2S Sensor Detection Mechanism

Hydrogen sulfide is oxidized at the sensing electrode:

H2S + 4H2O H2 SO4 + 8H+ + 8e-

The counter electrode acts to balance out the reaction at the sensing electrode by reducing oxygen present in the air to water:

2O2 + 8H+ + 8e- 4H2O

And the overall reaction is: H2S + 2O2 H2 SO4

4HS Signal Output: 0.07 μ A / ppm CO

MicroCel versus 4 Series H2S and CO Sensors

MicroCel versus 4 Series H2S and CO Sensors
  • Same "non consuming" chemistry as 4 Series sensors BUT:
    • MicroCel CO sensor has better internal filter, less cross sensitivity to VOCs than CO channel of COSH sensor
    • MicroCel H2S sensor based on the 4HS-LM "low methanol" electrode system (less cross sensitivity to interfering gases and VOCs)

City Technology 4 COSH Sensor

  • Dual channel "COSH" sensor
  • Single housing
  • Two independent outputs for H2S and CO measurement
  • Gas path through H2S first, CO 2nd
City Technology

City Technology 4 COSH Sensor

City Technology 4 COSH Sensor

H2S Gas Reaction:

H2S Sensing Electrode Reaction: H2S + 4H2O H2SO4 + 8H+ + 8e-

H2S Counter Electrode Reaction: 2O2 + 8H+ + 8e- 4H2O

Overall reaction: H2S + 2O2 H2 SO4

CO Gas Reaction:

CO Sensing Electrode Reaction: CO + H2O CO2 + 2H+ + 2e-

CO Counter Electrode Reaction: ½ O2 + 2H+ + 2e- H2O

Overall reaction: CO + ½O2 CO2

H2S signal output: 775 nA / ppm

CO signal output: 80 nA / ppm