Questions about Flame resistant clothing - Nomex, Carbon X

[Leozinho]

Does anyone have recommendations for cold weather, flame resistant long underwear? I've already replaced my silk-weight polypro with Smartwool for the next-to-skin base layer. Smartwool is not specifically flame/heat resistant but since it's wool it's better than standard synthetics.

However, I'm starting to think if might be worth it to by a set of nomex or Carbon X long underwear that offers more protection. Is anyone wearing this overseas?

A nomex flightsuit is another option but my assumption is that it would defeat the purpose to wear shrink-wrap polypro underneath it. Correct me if I'm wrong. The same may apply to your base layer. Is there any point of having a good flame heat resistant base layer like Carbon X if I wear a layer of synthetic snivel gear on top of it?

Thanks.