Gas leak detection: choosing the right sensor or flow monitor

Gas leaks can be detected in two fundamentally different ways: with a chemical gas sensor that measures the presence of the gas in the air, or with a flow monitor that signals a deviation in the gas flow. Both methods have their own field of application. The choice depends on the gas, the installation and the required response time. The ChemTec video below explains the difference clearly.

⏱ approx. 4 minutes reading time

Video: https://www.youtube.com/watch?v=SJbYjywriyc

Two approaches to gas leak detection

As a concept, gas leak detection covers two technically different approaches. A chemical gas sensor responds to the concentration of a specific gas in the ambient air. A flow monitor monitors the gas flow in a line and gives a signal as soon as the flow falls outside the set range. Both detect a gas leak, but at a different moment and from a different perspective.

Chemical gas sensor

Detects gas after it has already escaped and is spreading in the environment. Responds to concentration in the air.

Suitable as a safety layer for flammable, toxic or asphyxiating gases whose presence in the environment is dangerous.

Works independently of the piping and is therefore also effective for diffuse or hard-to-locate leaks.

Flow monitor (ChemTec)

Detects a leak via an unexpected rise or fall in the flow in the line, before the gas even reaches the environment.

Suitable as process protection for controlled gas lines, cooling circuits, analytical instruments and process lines.

Also gives an alarm for low flow (blockage, closed valve) and high flow (line break, loose connection).

When do you use both at the same time?

In critical systems, both layers make sense. The flow monitor detects deviations in the line directly and automatically. The chemical gas sensor acts as a safety net for gas that escapes nonetheless, or as a safety layer for personnel. In semiconductor production, laboratories and hydrogen installations, this combined approach is common.

When is a flow monitor the better choice?

A flow monitor is particularly effective in situations where the gas leak occurs in a closed piping circuit and the flow changes measurably. The ChemTec FAV, LCA and CCM series are adjustable flow monitors that provide a switching output as soon as the flow rises above or falls below the set setpoint. That setpoint can be adjusted without tools, making them flexible to use in systems with varying process parameters.

An EFV is not a flow monitor

An excess flow valve (EFV) responds automatically and mechanically to a sudden overshoot of the maximum flow, for example in the event of a line break, by shutting off the flow immediately. A flow monitor gives a signal but does not shut off by itself. For complete protection, combine a flow monitor for continuous monitoring with an EFV as an automatic emergency stop in the event of an incident.

The ChemTec flow monitor series at a glance

ChemTec has been producing flow monitors, flow meters and excess flow valves in-house in the USA since 1968. All products are designed, manufactured and tested in its own factory in Deerfield Beach, Florida. The range focuses specifically on low-flow applications for gases and liquids in analytical, medical, semiconductor and industrial environments.

ChemTec flow monitors and excess flow valves at Inacom

The complete ChemTec range is available via Inacom for the Dutch market. Inacom provides advice on the right choice of series, the setpoint range and the choice of materials for your specific gas and process environment. Custom and non-standard versions are available from ChemTec on request.

Want to know more?

Also see the knowledge base section Flow monitoring and flow protection for more in-depth articles on flow monitoring in semiconductor production and the difference between flow monitoring and flow protection as two complementary layers in a safe process system.