Do now
- Get inside the most central or below-ground space of a solid building, within minutes.
- If you were outside, strip off your outer clothes and bag them.
- Shower or wipe down your skin and hair. No conditioner.
- Seal the gaps in the room.
Then
- The rule is distance, shielding, time.
- Stay inside for 24 to 72 hours minimum. Fallout radiation drops about 90% in the first 2 days.
- Drink your stored water.
- Tune the crank radio for official word.
- Your stores make sheltering in place straightforward. This is what they are for.
Never
Related: B1 (Water), B5 (Medical, sanitation, hygiene), B6 (Comms, info, navigation)