💡 3 Key Points
- Gas sensors can respond to gases other than their target gas — this is called cross-sensitivity or interference.
- Interference can cause readings to appear higher or lower than actual; low readings are more dangerous.
- In complex gas environments, expert guidance on sensor type and interference characteristics is essential for accurate measurement.
What Is Gas Sensor Cross-Sensitivity (Interference)?
Gas detectors are designed to detect specific gases. However, real industrial sites rarely contain just one gas. In sewers, hydrogen sulfide (H₂S) and methane (CH₄) occur together; in boiler rooms, carbon monoxide (CO) and nitrogen dioxide (NO₂) may be detected simultaneously.
In environments where multiple gases coexist, a sensor may respond to gases other than its target and display incorrect readings — this is called cross-sensitivity or interference.
| Type | Effect | Risk Level |
|---|---|---|
| Positive (+) Interference | Reading higher than actual → unnecessary alarms, work stoppages | ⚠️ Moderate |
| Negative (−) Interference | Reading lower than actual → no alarm even at dangerous concentrations | 🔴 Very High |
Cross-Sensitivity by Sensor Type
① Electrochemical Sensors — CO, H₂S, O₂, NO₂, etc.
| Target Sensor | Interfering Gas | Type | Field Impact |
|---|---|---|---|
| CO sensor | H₂S | 🔴 Positive | H₂S misread as CO; false alarms |
| CO sensor | NO₂ | 🔵 Negative | CO reads lower than actual |
| H₂S sensor | SO₂ | 🔵 Negative | H₂S reads lower; alarm fails to trigger |
| NO₂ sensor | Cl₂ | 🔴 Positive | Cl₂ misread as NO₂ |
② Catalytic Bead Sensors (LEL) — Combustible Gas Measurement
Catalytic bead sensors can be permanently poisoned by silicone compounds, lead, and chlorinated solvents — causing them to display 0% even when combustible gas is present. This is among the most dangerous failure modes.
③ PID Sensors — VOC Measurement
PID sensors use different response factors (RF) for each VOC. With mixed VOCs, the displayed reading may be far from the actual concentration of any specific gas. Expert identification of the target compound is essential.
Expert Consultation: Why It Matters
WANDI Korea (wandi.co.kr) is a specialized gas detection company with decades of field experience, offering:
- Site gas environment analysis and interference risk assessment
- Sensor type recommendations (EC, Catalytic, PID, IR) based on actual field conditions
- In-house calibration and A/S with 5-business-day turnaround
- Regulatory compliance consulting (Korean OSHA confined space requirements)
📞 Expert Consultation on Sensor Interference
Share your site's gas conditions and we'll analyze interference risks and recommend the optimal sensor configuration.