Founded in 1939, Norwegian brand Aclima makes everything you need for the cold except the outer shell. Their wool under garments and mid-layers are well known throughout Europe and they have provided long underwear to the Norwegian Army since the 1969.
Over the past several years they have offered FR mesh underwear. Not only does the knit construction help with mositure and tempearture management but the 85% Rhovyl / 15% Modal (Lenzig fibers) is FR.
Tags: Aklima
Mesh underwear also increases your looks by at least 15%!
I have yet to try them myself, but Norwegian buddies swear by them…
I may ask my partner to put it on for some kinky tactical indoor games…