..a quick search, found this..some details on the discussion Beyond the burn: Studies on the physiological effects of flamethrowers during World War II | Military Medical Research | Full Text
Interesting. the CO level going high up is the "killer" not the 02 level going down due to the flamethrower.
..was watching something yesterday on flamethrowers.....the video showed how they built a spider trench...then placed a camera in the bunker...I'm guessing the camera was protected ...then they flamed it with a flamethrower ....it is more or less impervious to standard small arms/mg--but not the flamer here, flamer on a spider trench-----you don't want to be in that trench