Electrochemical Toxic Gas Sensor Technology

Substance-specific electrochemical sensors

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

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

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)

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