What Is a Gas Measuring Instrument? Types and Selection Criteria
A gas measuring instrument is a portable device that measures the concentration of a specific gas such as carbon monoxide, carbon dioxide, oxygen or flammable gas, or locates a leak.
A gas measuring instrument is a portable device that measures the concentration of a specific gas in the air or locates a gas leak. It is used for carbon monoxide screening around boiler rooms and combi boilers, for carbon dioxide monitoring that shows whether ventilation is adequate in enclosed spaces, for checking oxygen and toxic and flammable gases before entering confined spaces, and for finding refrigerant leaks in air-conditioning and refrigeration circuits. Each device shows only the gas its own sensor detects.
Types
| Type | Measures | Use | Catalog model |
|---|---|---|---|
| Carbon monoxide (CO) meter | CO, ppm | Boiler rooms, flues and around combi boilers | UNI-T UT337A |
| Carbon dioxide (CO2) meter | CO2, ppm; temperature and humidity | Ventilation checks in offices, classrooms and meeting rooms | Unit A37 |
| Multi-gas detector | O2, CO, H2S and flammable gas | Confined space entry | UNI-T UT334E+ (4-in-1) |
| Refrigerant gas leak detector | Refrigerant leaks | Air-conditioning, refrigeration and heat pump circuits | UNI-T UT336A; UT336B (semiconductor sensor) |
Selection criteria
- Target gas: First decide which gas is to be measured. A CO meter does not show CO2 and a CO2 meter does not show CO; oxygen deficiency can only be seen with an O2 sensor.
- Measuring range and unit: Toxic gases are read in ppm, oxygen in percent by volume (% vol) and flammable gas as a percentage of the lower explosive limit (% LEL). The highest expected value must fall within the instrument's range.
- Sensor type: The UT334E+ product data states electrochemical sensors for toxic gases and oxygen and a catalytic combustion sensor for flammable gas; the UT337A has an electrochemical CO sensor. Electrochemical sensors have a limited life; find the replacement interval in the manufacturer's datasheet.
- Refrigerant compatibility: Compare the refrigerant group the leak detector senses with the gas in the system; for systems with flammable refrigerants in particular, confirm in the datasheet that the detector is suitable for that gas.
- Explosive atmospheres: For use where flammable gas may be present, look for the Ex (ATEX) marking. The catalog product names carry no such declaration; request the document from the manufacturer if needed.
Common mistakes
- Measuring the wrong gas: Looking for carbon monoxide around a combi boiler with a CO2 meter; the reading suggests safety but CO has not been measured.
- Using a portable instrument instead of a fixed alarm: A handheld device only shows the moment of measurement; spaces that need continuous monitoring and warning need a fixed gas alarm system.
- Skipping bump tests and calibration: A multi-gas detector should be tested with a known gas before each use and calibrated at regular intervals.
Related standard
- EN 60079-29-1: Performance requirements for detectors for flammable gases in explosive atmospheres. Where flammable gas readings enter a formal assessment, request the instrument's certificate of conformity to this standard from the manufacturer.
Brands in the catalog
All 6 active products in the Gas Measuring Instruments category are Unit models; price and lead time are given on quotation. Five of them are gas instruments (UT337A, A37, UT334E+, UT336A, UT336B); the UT334A in the category is a radiation dose meter, not a gas instrument. For particle (PM2.5) measurement see Air Quality Meters, and for pressure and vacuum measurement in refrigeration circuits see Manometers.
Frequently asked questions
What is the difference between a carbon monoxide meter and a carbon dioxide meter?
Carbon monoxide (CO) is a toxic gas produced by incomplete combustion and is checked around boilers, flues and combi boilers. Carbon dioxide (CO2) rises with breathing and shows whether ventilation in an enclosed space is adequate. The two gases are measured with different sensors; one cannot replace the other.
Which gases does a 4-in-1 gas detector measure?
The UNI-T UT334E+ measures oxygen (O2), carbon monoxide (CO), hydrogen sulphide (H2S) and flammable gas together. It is used before entering confined spaces to check oxygen deficiency, toxic gas and explosion risk with one instrument.
How is a refrigerant gas leak detector used?
Switch the instrument on in clean air and let it warm up, then move the probe slowly over connection points such as joints, fittings and valves. The instrument's alert speeds up as you approach the leak. The exact spot can be confirmed with leak detection foam.
Can a portable gas meter replace a fixed gas detector?
No. A portable instrument shows the moment and place of measurement. A system that monitors a space continuously, warns of a leak and shuts off the valve when necessary is built with a fixed gas detector.