I'm grateful to Frank Finan for publishing so many great videos
of compressor stations and gas facilities with his FLIR camera,
however I've been a little frustrated by available guides online
about how to read them.
So I studied one of Frank's videos* until I figured it out.
(* = https://www.youtube.com/watch?v=m9rLv4bDhDM )
This inforgraphic is not copyrighted and is in the public domain.
I hope this is helpful.
UPDATE: it has been pointed out that raw hydrocarbon gasses are IR absorbers, or are opaque to IR. Either way, they will appear cool on the FLIR image. This is because the FLIR only displays a single axis of information. So to read these images, one must first be able to identify what color represents hot, then look to the other end for raw hydrocarbons.
Pointing the FLIR at hot objects is not terribly interesting. Yes, and exhaust stack of a compressor station is hot, and producing toxic emissions (CO2, CO, NOx, SO2, etc). Where the FLIR shines is in detecting raw gasses. These gasses will not appear hot for two reasons. First (as already mentioned), these gasses are IR absorbers. Second, because these gasses are typically COLD. This is because they are compressed inside a pipeline. The compression side produces heat inherently, and on the decompression side, this is inherently cooling. (this is the principle behind how an air-conditioner works).
Again, I hope this is helpful.
If I have gotten any of this wrong, please let me know and I will make corrections.