After the nuclear apocalypse there are pockets of radiation covering Russia. Artyom has a gas mask to protect himself from most of Russia's dangers, but it's use isn't fully explained.
Does radiation exposure in the wasteland have any long-term effects or does it only deal short-term damage? Similarly, does Artyom need to wear his gas mask when entering all radiation hot zones? If so, does the gas mask reduce or fully negate damage from radiation?