How long do you need to mask for a nuclear explosion?

In the context of a nuclear explosion, the correct understanding is that masking, or the use of protective masks, is not necessary in the immediate aftermath of a nuclear detonation due to the nature of the threat. A nuclear explosion generates a massive fireball and a shockwave followed by the fallout of radioactive materials, which present different types of hazards.

The priority after a nuclear explosion is to find shelter and protect oneself from the immediate radiation and thermal effects rather than focusing on using a mask. While protective masks can be valuable against certain chemical and biological agents or for filtering particulates, the overwhelming initial hazards posed by blast waves and heat require immediate evacuation to a protected area, typically some underground or reinforced structure, rather than relying on mask usage.

In situations some distances away from the blast, masks could be relevant during fallout periods if radioactive dust is present, but the immediate response to the explosion itself does not include masking. Therefore, understanding that masks are not applicable in the context of nuclear explosions directly addresses the scenario presented in the question.