PPM-M in Methane Detection

In methane detection, parts-per-million–meter (ppm-m) is a path-integrated gas concentration unit that refers to how much gas is present along a column of gas. More specifically, path-integrated concentration is the summation (i.e. integration) of the concentration of molecules through each measured meter of the column. It’s used in remote sensing systems (like aerial LiDAR, or other remote sensors) where gas concentration is measured from afar, rather than a single point such as a sensor within a gas plume.

Ppm-m is distinct from ppm (parts per million) which tells you how much methane is in a specific spot. Ppm-m tells you how much methane exists along the full length of the measurement beam. That makes it a key metric for technologies like Bridger’s Gas Mapping LiDAR® (GML) technology, which detects methane from aircraft by measuring laser light absorption through a gas plume.

Why Does PPM-M Matter in Methane Detection?

Ppm-m matters because remote gas sensors (like Bridger’s GML technology) don’t measure concentration at a single point, but instead they measure how much methane exists along a full line-of-sight through a plume.

With remote sensing of gas concentrations using units of ppm-m, operators can:

• Create plume imagery showing where the methane is and how much is there
• Reveal leak source locations to pinpoint where methane is escaping
• Support accurate emission rate quantification

Ultimately, path integrated concentration measurements in units such as ppm-m provide the foundation that makes remote plume imaging, leak localization, and accurate emission quantification possible.

How PPM-M Works in Methane Detection (Brief Technical)

Remote gas sensing technologies don’t take samples at a single point. Instead, they measure how much methane is present along an entire column of a gas plume. In the case of aerial LiDAR methane gas detection, as methane molecules absorb some of the light in the eye-safe laser beam, the sensor calculates the total amount of gas along the path. That total is reported in ppm-m.

For example, if there’s 15 ppm of methane stretched evenly over 100 meters, the path-integrated concentration would be 1500 ppm-m. If there’s 15 ppm over 10 meters, the path-integrated concentration would be 150 ppm-m. 

Key Applications in Oil and Gas

• Understanding types of gas detection technologies
• Identifying leak sources for faster mitigation
• Measuring plume concentration and extent during aerial scans
• Creating gas plume imagery and quantifying emission rates
• Supporting data transparency in methane reporting programs

Related: Methane Detection Sensitivity, Aerial Methane Detection, Methane Quantification, Gas Mapping LiDAR

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