Ironically the previous shirts, pants and jackets being poorly fitted did a really good job for fire protection; if you look at the results from the burn testing, the areas that were fully covered generally signficantly reduced the burns received, but there was still some first/second degree burns in spots where both layers tend to touch the skin (like between the shoulder blades).
Around the waist, where most people have huge baggy pockets of fabric where generally almost no burns; the air pockets prevented any significant heat transfer.
If you haven't seen the test video, they basically took an old pair of NCDs, put it on a dummy in the middle of four flamethrowers, hit it with a five second blast, then did some analysis (it was kitted out with sensors to measure the max temp, heat flux, etc).
They were ugly and didn't fit well, but felt a lot better about my chances of being able to run up a ladder through a hot gas layer (in a Kootenay type experience), or being in a space where something flared off (like a gas turbine with an oil leak that shot a fireball into the engine room).
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