What does WANDI Korea do?

WANDI Korea is the official Korean distributor of WANDI environmental and gas measurement instruments, operated by RS Korea Co., Ltd. We provide sales, calibration, repair, installation, and technical support for portable and fixed multi-gas detectors and air quality monitoring systems, exporting to more than 20 countries with over 5,000 delivery records.

What products do you offer?

We supply portable multi-gas detectors (EDW100, EDW500, Gas Tiger series), fixed multi-gas detectors (FIX800, FIX900, FIX-AP), air quality monitoring systems (FIX5000), and gas leak detectors (GLD series) for industrial safety and environmental measurement.

Which gases can be measured?

Our instruments measure oxygen (O2), carbon monoxide (CO), hydrogen sulfide (H2S), combustible gases (EX), carbon dioxide (CO2), ammonia (NH3), and volatile organic compounds (VOC), among other hazardous and combustible gases found on industrial sites.

Do you provide calibration and repair services?

Yes. Beyond product sales, WANDI Korea provides in-house and national certified calibration, repair, installation, and ongoing technical support. Calibration and repair requests can be submitted through the quote/calibration/repair pages on our website.

How can I get a quote for a gas detector?

You can request a quote directly through the quote page on our website or through a nearby dealer. Let us know your application and target gases, and we will recommend a suitable model.

In which fields are the products used?

They are used across a wide range of industrial sites including laboratories, factories and plants, hospitals, military facilities, livestock and wastewater treatment, and construction sites for worker safety and environmental monitoring.

What Is Gas Sensor Cross-Sensitivity (Interference)? How to Choose the Right Sensor for Accurate Measurement

💡 Key Takeaways

Gas sensors can respond to gases other than their target gas — this is called "cross-sensitivity" or "interference."
Interference causes readings to appear higher or lower than actual concentrations, with under-reading being far more dangerous.
In complex gas environments, selecting the right instrument requires expert advice on sensor type and interference characteristics.

What Is Gas Sensor Cross-Sensitivity (Interference)?

Gas detectors are designed to detect specific gases. However, real industrial environments never contain just one gas. Sewers generate hydrogen sulfide (H₂S) and methane (CH₄) together, while boiler rooms may simultaneously produce carbon monoxide (CO) and nitrogen dioxide (NO₂).

The phenomenon where a sensor in a multi-gas environment responds to gases other than its target gas, displaying incorrect readings, is called "cross-sensitivity" or "interference."

📌 Two Types of Interference

Type	Effect	Hazard Level
Positive (+) interference	Reads higher than actual → unnecessary alarms and work stoppages	⚠️ Moderate
Negative (−) interference	Reads lower than actual → no alarm despite dangerous concentration	🔴 Very High

Why negative interference is more dangerous: when gas is present at a hazardous level but the detector reads low, workers continue operating without recognizing the danger.

Interference Mechanisms by Sensor Type

① Electrochemical (EC) Sensors — CO, H₂S, O₂, NO₂, etc.

Electrochemical sensors measure current generated when gas undergoes oxidation-reduction reactions in an electrolyte solution. The problem is that structurally similar gas molecules can trigger the same reaction.

🔴 Classic Dangerous Case: CO Sensor + H₂S Interference

When hydrogen sulfide (H₂S) enters a standard electrochemical CO sensor, the sensor mistakes it for CO — 1 ppm of H₂S may display as tens to hundreds of ppm of CO. Conversely, when SO₂ is present alongside an H₂S sensor, the H₂S reading appears lower than actual concentration.

Target Sensor	Interfering Gas	Type	Field Impact
CO sensor	H₂S (hydrogen sulfide)	🔴 Positive (+)	H₂S misread as CO → false alarm
CO sensor	NO₂ (nitrogen dioxide)	🔵 Negative (−)	CO reads lower than actual
H₂S sensor	SO₂ (sulfur dioxide)	🔵 Negative (−)	H₂S reads lower than actual → alarm not triggered
H₂S sensor	CO (carbon monoxide)	🔴 Positive (+)	H₂S reads higher than actual due to CO
NO₂ sensor	Cl₂ (chlorine)	🔴 Positive (+)	Cl₂ misread as NO₂
O₂ sensor	CO₂ (high concentration)	🔵 Weak negative (−)	O₂ reads slightly lower than actual

② Catalytic Bead (Pellistor) Sensors — Combustible Gas (LEL) Measurement

For catalytic bead sensors primarily used for combustible gas (EX/LEL) measurement, the key interference issue is "poisoning." Silicone compounds, lead, chlorine-based solvents, and similar substances deactivate the catalyst surface, creating a fatal error where the sensor reads 0% even with combustible gas present.

Catalytic Bead Sensor Poisoning Substances

Poisoning Substance	Common Source Environments	Result
Silicone (Si) compounds	Sealant, coating, waterproofing sites	Catalyst poisoning → permanent sensitivity loss
Lead (Pb) compounds	Battery factories, lead work sites	Catalyst deactivation → gas not detected
Chlorinated solvents (TCE, etc.)	Cleaning agents, painting sites	Short-term suppression → reading distortion
High concentration H₂S	Wastewater treatment plants, waste tanks	Catalyst surface contamination → measurement failure

③ PID Sensors (Photo-Ionization Detectors) — VOC Measurement

PID sensors use ultraviolet (UV) light to ionize gas molecules and measure concentration. The sensitivity to each gas relative to the reference gas (isobutylene) is expressed as a "Response Factor (RF)." The same concentration of different VOCs will produce very different readings. When multiple VOCs are present on-site, it becomes impossible to attribute readings to a specific gas.

VOC Type	Response Factor (RF)	Display at 100 ppm actual
Isobutylene (reference)	1.0	100 ppm
Toluene	0.5	200 ppm (2x over-reads)
Ethanol	9.0	11 ppm (1/9 under-reads)
Acetone	1.1	91 ppm (slightly under-reads)
Methylene chloride	4.0	25 ppm (1/4 under-reads)

Industrial gas measurement expert analyzing sensors — In complex gas environments, expert analysis of sensor interference characteristics is the starting point for accurate measurement (Source: Unsplash / ThisisEngineering)

Why Interference Is a Real Danger on Site

Interference isn't just about a number being wrong. Incorrect readings directly affect workers' safety decisions.

📋 Real Danger Scenarios from Interference

1Scenario A — Alarm Not Triggered
H₂S reaches 50 ppm at a wastewater plant, but SO₂ interference causes the meter to display 5 ppm. No alarm sounds; the worker continues without awareness → collapses from hydrogen sulfide exposure.
2Scenario B — Frequent False Alarms Lead to Alarm Fatigue
A CO sensor continuously triggers false alarms due to H₂S interference. Workers learn to dismiss alarms as "false" → real CO leaks go unheeded.
3Scenario C — LEL Sensor Poisoning Causes Explosion
LEL sensor is poisoned by silicone coating agents on-site. When combustible gas leaks, the sensor reads 0% → explosion occurs.

Choosing the Right Sensor: Why Expert Guidance Is Essential

Interference is not a problem that's simply "solved by buying a better device." The degree of interference varies depending on the types of gases on site, concentration ranges, mixing ratios, and temperature/humidity conditions — so sensor type selection must come after comprehensive analysis of the target gases and site environment.

Selection Criterion	What to Verify	When Expert Advice Is Needed
Gas types present	Single gas vs. multiple gas environment	Environments with 2+ gas types generated simultaneously
Presence of interfering substances	Use of silicone, lead, or chlorine-based materials	Sites with poisoning risk (painting, coating, battery factories)
Concentration range	ppm-level vs. %-level	Environments requiring low-concentration, high-precision measurement
Sensor type suitability	Selecting the right type from EC / LEL / PID / IR	VOCs, special gases, or non-standard gases
Regulatory compliance	Meeting OSH Act measurement requirements	Sites with mandatory confined space measurement obligations

💡 Key Point

Even at the same site, the right sensor type changes depending on which gases co-exist. Internet searches and catalogs alone are insufficient to fully understand interference characteristics. Expert guidance from a specialist gas detector company that can evaluate dozens of gas-sensor combinations against your site conditions is essential.

Choose the Right Sensor with Expert Support

A gas detector's purpose is not just the purchase itself, but accurately detecting hazards at the site. Sensor selection that ignores interference can create a dangerous false sense of security — "we're monitoring" — when the readings may be meaningless.

WANDI Korea (wandi.co.kr) is a specialist company with decades of field experience in gas detection, offering the following expert services:

🔹
Site gas environment analysis
Analyzes gas types, concentrations, and mixing conditions to identify interference risks in advance.
🔹
Optimal sensor type recommendation
Recommends the right detector for your site by considering interference characteristics of EC, Catalytic, PID, and IR sensor types.
🔹
In-house calibration and A/S
One-stop service for sensor replacement, calibration, and repair — receivable within 5 business days.
🔹
Regulatory compliance consulting
Guidance on confined space gas measurement obligations and data retention requirements under the OSH Act.