Gas Sensor Cross Sensitivity (Tables)

There is no such thing as a perfect gas sensor. All gas sensors have a sensitivity to other gases. The question is to what degree? Defining this degree of sensitivity is a term called cross sensitivity.

Pros

Cons

✅ Low Cost: Electrochemical sensors, catalytic sensors and semiconducting metal oxide sensors are low cost.✅ Applications: The majority of applications used in our modern day life can operate with standard low cost sensors. ✅ Easy : Gas sensors are easy to design within electronics. ✅ Safety: Gas sensors offer many industries extra safety that save many lives every year.

⛔ Expensive: Infra Red sensors and PID sensors can get expensive. ⛔  Knowledge: People assume gas sensors are perfect, and are 100% specific. This is never the case. ⛔ Effort: It takes time and effort to understand a gas sensors characteristics and cross sensitivity behavior. ⛔ Information: Gas sensor  cross sensitivity information is limited, and this article aims to present the most comprehensive list.

What is Gas Sensor Cross Sensitivity

While a sensor may be primarily designed to detect a specific gas, it will exhibit a response to other gases. This cross sensitivity can potentially lead to inaccurate measurements or false alarms if not properly accounted for or calibrated. 

What Factors Determine Cross Sensitivity?

The fundamentals of electrochemical gas sensors involve the oxidation or reduction of the target gas at the electrode surface, which generates a current proportional to the gas concentration. Cross sensitivity occurs when other gases also react with the electrode surface and produce a current, which interferes with the target gas signal. The degree of cross sensitivity depends on various factors, such as the electrode material, the gas diffusion rate, test flow rates, sensor age, calibration exposure time, soak time, recovery time since prior exposure and the operating temperature and humidity. 

How Can I Minimize Cross Sensitivity?

To minimize cross sensitivity, several strategies can be employed, such as using gas filters, optimizing the sensor design, and applying calibration and compensation techniques.

What type of Cross Sensitivities Are There?

• Positive Response: The sensor responds to the target gas and another gas. This response gives the user the impression that there is target gas present when there isn’t or more target gas present than is the case. 
• Negative Response: The sensor produces a reduced response to the target gas and may neutralize the positive response from the target gas. This often occurs when both reducing and oxidizing gases are present that can cancel the sensor output signal. From the safety standpoint, a negative cross-sensitivity presents a higher risk than a positive one, as it will diminish the response to the target gas and may prevent an alarm.
• Inhibition: A gas or gas matrix inhibits the detection the target gas analyte from creating a positive sensor response.

Cross Sensitivity and Surrogate Gas

In some cases, the cross sensitivity behavior of a sensor is used for calibration purposes. This is only done when the target gas in unavailable in calibration gas form. Some examples include Hydrogen Peroxide and Chlorine Dioxide gas. In these cases, surrogate calibration must only be performed in a controlled laboratory environment, since cross sensitivity magnitudes can vary due to temperature, exposure time, soak time, sensor age, humidity, and gas flow rates. 

Cross Sensitivity Tables

Below we have composed the most comprehensive Cross Sensitivity Tables. This data has been collected over the many years of experience and testing, and in depth literature analysis from a plethora of trusted gas sensor suppliers. 

Treat the tables as estimates since cross sensitivity magnitudes may vary based on sensor design and test conditions. In addition, gas mixtures (gas matrix) are rarely tested and results with mixed gases are unpredictable. The table is organized in alphabetic gas order.

Acrylonitrile (C3H3N)

Sensor Type: Electrochemical Gas Sensor
Product: NA

Gas	Concentration (ppm)	Output Signal (in ppm C2H2)
Acetylene	10	10
Hydrogen Sulfide	50	< 1.0
Sulfur Dioxide	10	< 1.0
Nitric Oxide	50	< 1.0
Formaldehyde	10	< 1.0
Ammonia	50	0.0
Carbon Monoxide	100	< 1.0
Ethylene	100	< 1.0
Vinyl Chlorine	100	< 1.0
Ethanol	200	< 1.0

Acetylene (C2H2)

Sensor Type: Electrochemical Gas Sensor
Product: FD-90A-C2H2

Gas	Concentration (ppm)	Output Signal (in ppm C2H2)
Acetylene	10	10
Hydrogen Sulfide	50	< 1.0
Sulfur Dioxide	10	< 1.0
Nitric Oxide	50	< 1.0
Formaldehyde	10	< 1.0
Ammonia	50	0.0
Carbon Monoxide	100	< 1.0
Ethylene	100	< 1.0
Vinyl Chlorine	100	< 1.0
Ethanol	200	< 1.0

Alcohol (CH ₃CH ₂OH)

Gas	Concentration (ppm)	Output Signal (in ppm C2H2)
Alcohol	10	10
Carbon Monoxide	100	60
Isobutylene	20	28

Acid Organic (R-COOH)

Gas	Concentration (ppm)	Output Signal (in ppm R-COOH)
Organic Acids	10	10
Chlorine	20	150
Methanol	150	0
Ammonia	80	-12
Nitrogen Dioxide	5	30
Ozone	1	5
Sulfur Dioxide	5	> -25

Ammonia (NH3)

Sensor Type: Electrochemical Gas Sensor
Product: FD-90A-NH3

Gas	Concentration (ppm)	Output Signal (in ppm NH3)
Ammonia	10	10
Hydrogen Sulfide	25	22.0
Carbon Dioxide	5,000	0.0
Carbon Monoxide	100	0.0
Hydrogen	1,000	0.0
Isobutylene	100	0.0
Ethanol	200	< 1.0

Arsine (AsH3)

Sensor Type: Electrochemical Gas Sensor
Product: NA

Gas	Concentration (ppm)	Output Signal (in ppm AsH3)
Arsine	10	10
Sulfur Dioxide	10	1.5
Nitric Oxide	35	-0.5
Ammonia	30	0.0
Hydrogen	1000	0.7
Nitrogen Dioxide	10	-2.0
Hydrogen Sulfide	2	1.8
Carbon Dioxide	5000	0.0
Chlorine	10	-1.3
Ethylene	50	0.0
Carbon Monoxide	100	0.9

 

Benzene (C6H6) - PID sensors used 

Bromine (Br2)

Sensor Type: Electrochemical Gas Sensor
Product: FD-90A-Br2

Gas	Concentration (ppm)	Output Signal (in ppm Br2)
Bromine	10	2.5
Ethylene	100	0
Formaldehyde	7	0
Chlorine Dioxide	3	~3
Carbon Monoxide	300	0
Ethanol	60	0
Fluorine	8	~8
Hydrogen	100	0
Hydrogen Sulfide	20	< -20
Hydrogen Chloride	20	0
Ammonia	80	0
Nitric Oxide	50	0
Nitrogen Dioxide	20	~ 20
Ozone	1	~ 1
Sulfur Dioxide	5	0

Carbon Disulfide (CS₂)

Sensor Type: Electrochemical Gas Sensor
Product: FD-90A-CS2

Gas	Concentration (ppm)	Output Signal (in ppm CS₂)
Carbon Disulfide	10	10
Ethylene	100	< 2
Carbon Monoxide	1000	55 ± 10
Hydrogen	100	0
Hydrogen Sulfide	20	0
Nitric Oxide	100	0
Nitrogen Dioxide	20	0
Phosphine	20	0
Sulfur Dioxide	100	0

Carbon Monoxide (CO)

Sensor Type: Electrochemical Gas Sensor
Product: FD-90A-CO

Gas	Concentration (ppm)	Output Signal (in ppm CO)
Carbon Monoxide	10	10
Hydrogen Sulfide	15	-0.1
Sulfur Dioxide	10	-0.2
Nitric Oxide	50	-16.0
Nitrogen Dioxide	10	-2.6
Ammonia	50	0.0
Hydrogen	100	24.0
Ethylene	100	10.0
Chlorine	15	-0.5
Ethanol	200	1.5

Chlorine (Cl2)

Sensor Type: Electrochemical Gas Sensor
Product: FD-90A-Cl2

Gas	Concentration (ppm)	Output Signal (in ppm CL2)
Chlorine	10	10
Hydrogen Sulfide	10	-12.0
Sulfur Dioxide	20	0.0
Nitric Oxide	10	0.1
Nitrogen Dioxide	10	7.5
Ozone	10	10
Carbon Monoxide	100	0.0
Ammonia	100	0.1
Hydrogen	1,000	-0.1
Carbon Dioxide	30,000	0.0

Chlorine Dioxide (ClO₂)

Gas	Concentration (ppm)	Output Signal (in ppm CLO2)
Chlorine Dioxide	10	10
Hydrogen Sulfide	20	-5.0
Nitrogen Dioxide	10	14.0
Carbon Monoxide	100	0.0
Hydrogen	3,000	0.0
Chlorine	10	3.5
Carbon Dioxide	5,000	0.0

 

Combustible Gas (Catalytic Sensor)

Sometimes known as Flammable Gas or Explosive Gas.

Gas	Concentration (ppm)	Output Signal (in ppm CLO2)
Chlorine Dioxide	10	10
Hydrogen Sulfide	20	-5.0
Nitrogen Dioxide	10	14.0
Carbon Monoxide	100	0.0
Hydrogen	3,000	0.0
Chlorine	10	3.5
Carbon Dioxide	5,000	0.0

Diborane (B2H6)

Gas	Concentration (ppm)	Output Signal (in ppm B2H6)
Chlorine Dioxide	10	10
Hydrogen Sulfide	20	-5.0
Nitrogen Dioxide	10	14.0
Carbon Monoxide	100	0.0
Hydrogen	3,000	0.0
Chlorine	10	3.5
Carbon Dioxide	5,000	0.0

 

Ethylene (C2H4)

Gas	Concentration (ppm)	Output Signal (in ppm C2H4)
Ethylene	10	10
Hydrogen Sulfide	50	< 1.0
Sulfur Dioxide	100	< 1.0
Nitric Oxide	100	60.0
Formaldehyde	10	< 1.0
Ammonia	50	0.0
Carbon Monoxide	100	< 1.0
Acetylene	10	15.0
Vinyl Chloride	100	< 1.0
Ethanol	500	< 1.0

Ethylene Oxide (C2H4O)

Gas	Concentration (ppm)	Output Signal (in ppm ETO)
Ethylene Oxide	10	10
Carbon Monoxide	25	10.0
Isobutylene	50	45.0
Ethylene	50	35.0
Acetylene	50	35.0
Ethanol	100	45.0
Methyl Alcohol	30	25.0
Formic Acid	100	30.0

Formaldehyde (CH2O)

Gas	Concentration (ppm)	Output Signal (in ppm CH2O)
Formaldehyde	10	10
Carbon Monoxide	50	1.6
Ethanol	2,000	1.2
Acetic Acid	2,000	-0.3
Ethylene	100	0.3
Methyl Alcohol	100	0.1
Isopropanol	100	0.1

Fluorine (F2)

Gas	Concentration (ppm)	Output Signal (in ppm CLO2)
Chlorine Dioxide	10	10
Hydrogen Sulfide	20	-5.0
Nitrogen Dioxide	10	14.0
Carbon Monoxide	100	0.0
Hydrogen	3,000	0.0
Chlorine	10	3.5
Carbon Dioxide	5,000	0.0

 
Hydrogen (H2)

Gas	Concentration (ppm)	Output Signal (in ppm H2)
Hydrogen	10	10
Hydrogen Sulfide	25	0.0
Sulfur Dioxide	5	0.0
Carbon Monoxide	50	200.0
Nitric Oxide	35	< 10.0
Nitrogen Dioxide	5	0.0
Ethylene	100	80.0
Chlorine	10	0.0

Hydrogen Bromide (HBr)

Gas	Concentration (ppm)	Output Signal (in ppm HBr)
Hydrogen Bromide	10	10
Chlorine	20	-8
Carbon Monoxide	100	1
Hydrogen	1,000	<1
Nitrogen Dioxide	10	2
Sulfur Dioxide	20	52
Ethylene	100	1
Hydrogen Sulfide	5	60

Hydrogen Chloride (HCl)

Gas	Concentration (ppm)	Output Signal (in ppm HCL)
Hydrogen Chloride	10	10
Carbon Monoxide	100	0.0
Sulfur Dioxide	20	35.0
Nitric Oxide	20	50.0
Nitrogen Dioxide	10	1.0
Hydrogen	2,000	0.0
Hydrogen Sulfide	25	100.0
Nitrogen	100%	0.0
Chlorine	20	-5.0

Hydrogen Cyanide (HCN)

Gas	Concentration (ppm)	Output Signal (in ppm HCN)
Hydrogen Cyanide	10	10
Carbon Monoxide	300	0.0
Sulfur Dioxide	5	18.1
Nitric Oxide	35	0.0
Nitrogen Dioxide	5	-9.5
Hydrogen Sulfide	5	14.9
Ethylene	100	0.0
Carbon Dioxide	5000	0.0
Ethanol	600	0.0

Hydrogen Fluoride (HF)

Gas	Concentration (ppm)	Output Signal (in ppm HF)
Hydrogen Fluoride	10	10
Hydrogen Sulfide	25	-1.0
Sulfur Dioxide	20	-0.2
Nitric Oxide	50	0.0
Nitrogen Dioxide	5	4.3
Carbon Monoxide	100	0.0
Hydrogen	1,000	0.0

Hydrogen Peroxide (H2O2)

Gas	Concentration (ppm)	Output Signal (in ppm H2O2)
Hydrogen Peroxide	10	10
Sulfur dioxide	20	20 ± 12

Hydrogen Sulfide (H₂S)

Gas	Concentration (ppm)	Output Signal (in ppm H2S)
Hydrogen Sulfide	10	10
Carbon Monoxide	100	0.0
Nitric Oxide	50	-0.7
Nitrogen Dioxide	10	-2.1
Ammonia	50	3.8
Hydrogen	1,000	0.0
Chlorine	15	-7.8
Sulfur Dioxide	20	16.1
Ethylene	100	0.0
Ethanol	2,000	0.0

Mercaptan (CH4S)

Gas	Concentration (ppm)	Output Signal (in ppm CH3SH)
Methanethiol	10	10
Carbon Monoxide	50	< 5.5
Sulfur Dioxide	5	< 2.1
Nitrogen Dioxide	5	< -3.5
Nitric Oxide	25	0.0
Ammonia	50	0.0
Hydrogen	1,000	< 10.0
Hydrogen Sulfide	25	40.0

Nitric Oxide (NO)

Gas	Concentration (ppm)	Output Signal (in ppm NO)
Nitric Oxide	10	10
Hydrogen Sulfide	25	11.0
Carbon Monoxide	100	0.0
Nitrogen Dioxide	5	< 0.2
Sulfur Dioxide	5	< 0.3
Ethylene	100	0.0
Hydrogen	1,000	< 0.3

Nitrogen Dioxide (NO₂)

Gas	Concentration (ppm)	Output Signal (in ppm NO2)
Nitrogen Dioxide	10	10
Hydrogen Sulfide	15	< 1.0
Carbon Monoxide	300	< 1.0
Nitric Oxide	35	0.0
Chlorine	1	0.6
Sulfur Dioxide	5	-5.0

Ozone (O₃)

Gas	Concentration (ppm)	Output Signal (in ppm O3)
Ozone	10	01
Hydrogen Sulfide	20	-4.0
Sulfur Dioxide	20	< 1.0
Nitric Oxide	50	< 1.0
Nitrogen Dioxide	10	< 11.0
Carbon Monoxide	100	0.0
Ammonia	100	0.0
Hydrogen	1,000	0.0
Chlorine	10	9.0
Carbon Dioxide	10,000	0.0

Oxygen (O₂)

Gas	Concentration	Output Signal (% O2 equivalent)
Oxygen	10	10
Carbon Dioxide	5%	0.1
Hydrogen	2,000 ppm	-0.2

Phosgene (COCl2)

Gas	Concentration (ppm)	Output Signal (in ppm COCl2)
Phosgene	10	10
Chlorine	5	26.4
Carbon Dioxide	3,000	0.0
Carbon Monoxide	50	0.0
Hydrogen	1,000	0.0
Hydrogen Sulfide	5	-3.3
Ammonia	10	-2.5
Nitric Oxide	10	0.0

Phosphine (PH₃)

Gas	Concentration (ppm)	Output Signal (in ppm PH3)
Phosphine	10	10
Hydrogen Sulfide	15	12.0
Sulfur Dioxide	20	6.2
Ammonia	50	0.0
Hydrogen	1,000	0.0
Carbon Monoxide	1,000	0.0
Ethylene	100	0.0

Silane (SiH4)

Gas	Concentration (ppm)	Output Signal (in ppm SiH4)
Silane	10	10
Sulfur Dioxide	20	6.6
Nitric Oxide	50	0.0
Ammonia	50	0.0
Carbon monoxide	100	4.1
Nitrogen Dioxide	10	-3.1
Hydrogen Sulfide	2	1.7
Chlorine	15	-3.9

Sulfur Dioxide (SO₂)

Gas	Concentration (ppm)	Output Signal (in ppm SO2)
Sulfur Dioxide	10	10
Hydrogen Sulfide	15	0.1
Carbon Monoxide	100	0.0
Nitric Oxide	50	0.1
Nitrogen Dioxide	5	-5.5
Hydrogen	1,000	0.2
Ammonia	20	0.0
Chlorine	5	-1.5
Acetylene	10	< 2.0
Ethylene	50	0.2

Styrene (C8H8)

Gas	Concentration (ppm)	Output Signal (in ppm C8H8)
Sulfur Dioxide	10	10
Hydrogen Sulfide	15	0.1
Carbon Monoxide	100	0.0
Nitric Oxide	50	0.1
Nitrogen Dioxide	5	-5.5
Hydrogen	1,000	0.2
Ammonia	20	0.0
Chlorine	5	-1.5
Acetylene	10	< 2.0
Ethylene	50	0.2

Tetrahydrothiophene (C4H8S) THT

Gas	Concentration (ppm)	Output Signal (in ppm C4H8S)
Tetrahydrothiophene	10	10
Hydrogen Sulfide	25	8.5
Carbon Monoxide	50	0.1
Nitric Oxide	35	< 130.0
Sulfur Dioxide	5	0.0
Nitrogen Dioxide	10	16.0

Vinyl Chloride (C2H3Cl)

Gas	Concentration (ppm)	Output Signal (in ppm C2H3CL)
Vinyl Chloride	10	10
Carbon Monoxide	25	15.0
Isobutylene	50	35.0
Ethylene	50	65.0
Acetylene	50	85.0
Ethanol	100	55.0

Volatile Organic Compound  (VOC)

Gas	Concentration (ppm)	Output Signal (in ppm VOCs)
Volatile Organic Compound	10	10
Carbon Monoxide	100	45
Hydrogen	200	0
Hydrogen Sulfide	20	80
Nitrogen Dioxide	20	< 4

 

source https://www.forensicsdetectors.com/blogs/articles/gas-sensor-cross-sensitivity-ultimate-list