The masks worn during the Falklands were anti-flash equipment. They were intended to protect crewmen against bomb or missile explosions. These cause a short, high temperature flash fire, which was one of the major causes of casualties in WWI. Flash causes serious burns to exposed skin. The masks protect against flash in two ways. Firstly, they provide a barrier, directly protecting skin from flash. Secondly, the white colouring reflects the infrared light of the flash, which is the main way flash causes burns.

This is not intended to supplant an answer from one of the historians here, just a clarification as to what you're referring to. Do you mean these things?