regarding the infrared effect (Night vision) the rabbit mentioned that idea just to group the flames which may imply that evey flame you can see with infrared is a real flame (1) the others (0)
when you apply the infrared effect (which means you can see at night without any light) then the image looks like this: (Green colour is dominant)
https://imgur.com/a/tQC0Wthat particular effect doesnt do a great job of bringing much out.. one thing i noticed is that if you do a simple invert operation in gimp, the background to the flames comes out as a row of more standard-looking flames, with the white-orange-red sort of coloring..
https://imgur.com/a/YItrz