How to Choose the Right Industrial Detector: A Practical Selection Guide

I. Three crucial questions to ask before selecting a product

Before starting the technology selection process, three core questions need to be clarified:

1. What gas do I need to test for?

This is the most basic and crucial step. The physicochemical properties of different gases vary greatly, which directly determines the choice of sensor type.

Gas categories	Typical gases	Selection principles
combustible gas	Methane, propane, hydrogen, gasoline vapor	Catalytic combustion or infrared sensors are preferred.
Toxic gas	Hydrogen sulfide, carbon monoxide, ammonia, chlorine	Selecting an electrochemical sensor
VOCs	Benzene, formaldehyde, xylene	Selected PID photoionization sensor
oxygen	O₂	Selected electrochemical oxygen sensor

Special reminder : If the gas is both flammable and toxic (such as hydrogen sulfide or carbon monoxide), a Toxic Gas Detector should be installed according to GB/T 50493,because the lethal concentration of toxic gases is far below the lower explosive limit.

2. What is the on-site environment like?

Environmental factors directly affect the installation method and protection level requirements of the detector:

Is there any explosive gas present ? → Explosion-proof certification required.

Is it outdoors ? → IP protection rating required (IP65 or higher recommended)

Is there any corrosive substance present ? → Anti-poisoning sensor required.

Is there any vibration or impact ? → Reinforcement installation is required.

3. Do I need fixed monitoring or mobile monitoring?

Equipment type	Applicable Scenarios	Advantages
Fixed detector	Fixed locations such as production unit area, storage tank area, and pump room	24-hour continuous monitoring, with linked control equipment
Portable detector	Routine inspections, confined space operations, maintenance and repair	Flexible and mobile, personnel can carry it with them

II. Sensor Technology Selection: The Core of the Core

Sensors are the "heart" of detectors. Different technologies have their own advantages and disadvantages, and the choice should be made based on the gas being detected and the environment in which it is used.

Comparison of mainstream sensor technologies

Sensor type	Working principle	Applicable gases	advantage	shortcoming	Typical lifespan
Catalytic combustion	The combustion of gas on the catalyst surface causes a change in electrical resistance.	Combustible gases (alkanes)	Simple structure, low cost, and good linearity	Susceptible to poisoning (silicon, sulfur), requires oxygen	2-5 years
Electrochemistry	The gas undergoes a redox reaction with the electrode.	Toxic gases, oxygen	Good selectivity, low power consumption, and high precision	Short lifespan, affected by temperature and humidity	1-3 years
Nondispersive infrared	Gas molecules absorb infrared light of specific wavelengths	Methane, CO₂, refrigerant	Resistant to poisoning, requires no oxygen, and has a long lifespan.	High initial cost, not suitable for hydrogen	5-10 years
Photoionization	Ultraviolet photoionization of gas molecules	VOCs	Extremely high sensitivity (ppb level)	High cost, requires regular cleaning	Depending on the frequency of use

 

How to choose sensor technology?

Scenario 1: Common flammable alkane gases (methane, propane, etc.)

If the environment is clean and free of silicon/sulfur pollutants → catalytic combustion sensor (high cost-performance ratio)

If there is a risk of poisoning (chemical plant, sewage treatment plant) or potential oxygen deficiency → infrared sensor (reliable and durable)

Scenario 2: Toxic Gas Monitoring

When selecting an electrochemical sensor , choose the appropriate sensor model based on the specific gas type.

Scenario 3: Monitoring of Volatile Organic Compounds (VOCs)

When selecting a PID photoionization sensor , pay attention to whether the detection limit meets occupational exposure limits.

Scenario 4: Complex Environment (Petrochemical Plant, Oil Refinery)

Prioritize sensors with anti-poisoning capabilities . For example, the UGT-C5K anti-poisoning sensor from AirShield in the UK can operate continuously for 30 days in a 5ppm silicon vapor environment with only a 3% sensitivity decay (compared to over 40% for traditional products), making it particularly suitable for refining scenarios where silicon catalyst dust is present.

III. Explosion-proof rating and protection rating: Hard indicators of safety

1. Explosion-proof rating (Ex)

Detectors used in explosive gas atmospheres must obtain explosion-proof certification. According to GB/T 50493-2019 and the latest standards, the following markings should be considered when selecting a detector :

Example of explosion-proof marking	Meaning Interpretation
Ex d IIC T6 Gb	Explosion-proof type, suitable for Class II Class C gases (including hydrogen and acetylene), T6 temperature group (surface temperature ≤85℃), Gb level equipment.

Selection Recommendations :

For conventional petrochemical sites: Ex d IIB T6 Gb is sufficient.

For gases such as hydrogen and acetylene: Ex d IIC level must be selected.

T6 (85℃) is superior to T3 (200℃), so the higher temperature group should be selected whenever possible.

2. Protection Rating (IP)

The protection rating indicates the equipment's ability to resist dust and water, which is especially important for outdoor installations.

IP Level	meaning	Applicable Scenarios
IP65	Completely dustproof + water-resistant	outdoor general environment
IP66	Completely dustproof + Resistant to strong water spray	Harsh outdoor conditions (heavy rain, washing)
IP67	Completely dustproof + short-term water immersion	Low-lying areas that may accumulate water

Selection recommendations : For outdoor installation, it is recommended to choose at least IP65 , and for coastal and rainy areas, IP66 and above are recommended .

IV. Installation Method and Signal Output: Matching Site Conditions

1. Sampling method

Sampling method	Features	Applicable Scenarios
Natural diffusion	Gas diffuses naturally into the sensor	Open space, routine inspection
Pump suction type	Built-in air pump actively draws air	Confined space pre-inspection, long-distance leak detection, pipeline internal inspection

Selection Recommendations :

Fixed detectors: typically natural diffusion type

When a portable detector enters a confined space: a pump-suction type must be selected to allow for remote pre-detection before entry.

2. Signal output method

Fixed detectors need to be connected to a control system (DCS/PLC/GDS), and the signal type needs to be confirmed when selecting a model:

signal type	Features	Applicable Systems
4-20mA analog quantity	Classic analog signals, simple wiring	Traditional PLC/DCS system
RS485 bus (Modbus)	Digital communication can transmit multiple parameters.	Bus-based GDS system
Relay output	Switch signals directly control the equipment.	Fan, shut-off valve, audible and visual alarm
Wireless communication (NB-IoT/4G)	No wiring required, remote monitoring	Smart Industrial Park, Unmanned Station

Selection Recommendations :

For new projects: prioritize devices that support bus communication to save on cabling costs.

Upgrade project: Compatibility with existing control system signals needs to be confirmed.

For linkage control, select a model with relay output .

V. Functional Completeness: Standard Requirements under the New National Standard

GB 15322.1-2026 "Combustible Gas Detectors Part 1: Point-Type Combustible Gas Detectors for Industrial and Commercial Use" (implemented in August 2027),released in January 2026 , the new standard sets higher requirements for detector functionality  :

Requirements for adding/enhancing features

Function	Require	Selection Recommendations
Sensor lifespan reminder	Automatic reminder to replace upon expiration	Choose equipment with this function to avoid exceeding the service life.
Fault self-diagnosis	Automatic detection of sensor and circuit malfunctions	Ensure system availability
Historical records	Store alarms, faults, and operational data.	Facilitates accident tracing and safety auditing
Audio-visual self-test	Automatic audible and visual alarm function upon power-on	Ensure reliable alarm output
Wireless communication specifications	The technical requirements for wireless communication have been clarified.	Suitable for remote monitoring scenarios

Selection recommendation : Prioritize products that meet the requirements of the new national standard GB 15322.1-2026 to ensure that there will be no compliance risks due to standard upgrades during future acceptance and supervision.

VI. Life Cycle Cost Considerations

Procurement decisions should not only consider the initial purchase price, but also the total life cycle cost.

Cost items	low-end products	High-end products
Initial procurement costs	Low	Medium/High
Sensor lifespan	2-3 years	3-5 years (infrared can last up to 10 years)
Calibration/Maintenance Frequency	3-6 months/time	6-12 months/time
False alarm rate	High levels, impacting production	Low, reduce interference
Replacement cost	Frequent changes	Long-term replacement
Comprehensive cost	Possibly higher	Long-term better

Selection Recommendations :

Key process areas: Select high-quality, long-life products to ensure safe and continuous operation.

Non-critical areas: Cost-effective solutions can be chosen, but basic compliance requirements must still be met.

 

VII. Selection Decision Flowchart

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Start │ ▼ Determine the type of gas to be detected (combustible/toxic/VOCs/oxygen) │ ▼ Confirm the site environment (explosion-proof area? Outdoor? Corrosive?) │ ▼ Select sensor technology (catalytic combustion/infrared/electrochemical/PID) │ ▼ Confirm the installation method (fixed/portable) │ ▼ Determine the signal output (4-20mA/RS485/relay/wireless) │ ▼ Verify certifications (explosion-proof certificate/fire protection certification/IP rating) │ ▼ Assess the total life cycle cost │ ▼ Complete the selection

VIII. Practical Selection Checklist

Before placing your final order, please confirm the following items one by one:

✅ Compliance Check

Has the product passed the national fire protection certification (CCCF)?

Does the explosion-proof rating meet the on-site requirements?

Does it comply with the GB/T 50493-2019 design standard?

Does it meet the requirements of the upcoming new national standard GB 15322.1-2026?

✅ Technical Parameter Check

Does the detection range cover the expected concentration?

Is the alarm error ≤ ±3%LEL (flammable) or ≤ ±5%FS (toxic)?

Does the response time meet the requirements (generally T90≤30 seconds)?

Does the operating temperature range cover the on-site environment?

✅ Installation compatibility check

Does the installation height conform to the gas density principle (0.3-0.6m for heavy gas, near the roof for light gas)?

Is the signal output compatible with the control system?

Is the power supply voltage compatible (DC24V is common)?

IX. Conclusion

Choosing the right industrial detector essentially involves finding the optimal balance between safety requirements, technical performance, environmental conditions, and cost budget . With the successive release and implementation of new standards such as GB/T 46692.2-2025 and GB 15322.1-2026, the industry is upgrading towards higher reliability, stronger environmental adaptability, and greater intelligence.

For corporate procurement personnel and safety managers, "compliance" is merely the bottom line; "applicability" is the key . During the selection process, it is recommended to have in-depth communication with professional suppliers regarding on-site conditions, and, if necessary, conduct on-site surveys and solution demonstrations to ensure that the selected detectors truly become "reliable sentinels" protecting the company's safe production.