There are many factors to consider when selecting a gas flowmeter, but the following four are the most core and critical factors and can serve as a basic framework for selection:
1. Gas Properties
This is the primary consideration for selection and directly determines the flowmeter type and some materials.

Gas Composition: Is it a single gas (such as nitrogen or oxygen) or a mixed gas? If it is a mixed gas, are the proportions of the components fixed? Clean gases and corrosive gases (such as chlorine and ammonia) require completely different flowmeter materials.

Cleanliness: Is the gas clean? Does it contain impurities such as dust, oil, and liquid droplets? Impurities can clog or damage certain types of flowmeters (such as thermal and vortex types).

Humidity: Is the gas dry or humid? Moisture can condense, affecting measurement accuracy and even damaging the sensor.

Temperature and Pressure: What is the operating temperature and pressure range of the gas? This affects the flowmeter's pressure capacity, sealing, and whether temperature and pressure compensation is required to convert the operating flow rate to a standard flow rate.

2. Flow Range
This is key to ensuring the flowmeter is usable and effective.

Expected Flow Range: You need to clearly define the minimum, maximum, and typical flow rates for the gas. The most important principle is that the typical flow rate should fall in the upper middle range of the flowmeter's range (e.g., 30%-80% of the range), not near its minimum or maximum limits.

Turndown: This refers to the ratio of the maximum flow rate to the minimum flow rate that the flowmeter can accurately measure. If your flow rate fluctuates significantly, you should choose a flowmeter with a wide turndown ratio (such as a thermal mass flowmeter or Coriolis mass flowmeter).

Diameter: Choose the appropriate pipe diameter based on the flow range. Too large a diameter will prevent measurement of small flows or result in extremely poor accuracy; too small a diameter will result in excessive pressure loss and even damage the flowmeter.

3. Performance Requirements
This determines whether the measurement results meet your process or monitoring needs.

Accuracy: What level of measurement accuracy do you require? Is the measurement used for trade settlement (requiring high accuracy) or process control (requiring stability and repeatability)? Higher accuracy generally comes with higher costs.

Repeatability: The ability of a flowmeter to repeatedly display the same reading under identical conditions. For process control, good repeatability is sometimes more important than high accuracy.

Response Time: How quickly a flowmeter reacts to changes in flow rate. For circuits requiring rapid control, this response time must be sufficiently short.

4. Installation Conditions and Operating Environment
This determines whether the flowmeter can be successfully installed and operate stably over the long term.

Pipe Orientation: Is the pipe horizontal, vertical, or inclined? Some flowmeters (such as differential pressure and turbine types) have strict requirements for installation orientation.

Straight Pipe Length Requirements: Most flowmeters (especially vortex, turbine, and differential pressure types) require sufficient straight pipe length to ensure stable flow patterns and obtain accurate measurements. If installation space is limited, select a flowmeter with low straight pipe length requirements (such as thermal or Coriolis).

Ambient Temperature: Check whether the ambient temperature at the installation site is within the allowable operating range of the flowmeter's electronics.

Explosion-proof requirements: If the site is in a flammable or explosive environment, a flowmeter with the appropriate explosion-proof certification (such as Ex d or Ex ia) must be selected.

Output signal and communication protocol: What output signal is required (4-20mA, pulse)? Is an on-site display required? Are communication functions (such as HART, Profibus, Modbus) required?

Summary and selection process recommendations
First, clarify "what to measure": List all gas properties in detail.

Next, determine "how wide to measure": Determine the actual flow range and pipe diameter.

Next, determine "how accurate": Determine the accuracy and performance requirements based on the application scenario.

Finally, check "how to install": Check the on-site installation conditions and environmental restrictions.

By summarizing these four factors, you can then select the appropriate flowmeter type. (For example, for clean, medium-to-large-caliber, high-flow air, consider a vortex flowmeter; for low-flow, wide-turndown gas, consider a thermal mass flowmeter; and for applications requiring high-precision measurement without cost considerations, consider a Coriolis mass flowmeter.)

The best approach is to contact us immediately so we can recommend the right gas product for you.