Comprehensive survival guidance based on up‑to‑date U.S. federal sources (CDC / FEMA / HHS)
Flash, Drop & Cover (Seconds)
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If you see an intense flash (even before noise arrives), don’t look at it—turn your head away, close your eyes, and drop face‑down on the ground (< 1 sec) to protect against thermal radiation and potential blast debris. Tell children: “Turn → drop flat → cover.”
oai_citation:0‡Reddit -
Stay prone until the shock wave passes, usually seconds to tens of seconds later.
oai_citation:1‡Wikipedia
Indoors vs. Outdoors: What to Do Next (1–5 minutes)
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Outdoors or in a car: Move immediately to the nearest robust building. Aim for brick, concrete, or preferably a basement.
oai_citation:2‡Florida Disaster -
Already indoors? Go toward the interior-most room or basement, stay away from windows, and avoid the roof or exterior walls.
oai_citation:3‡FEMA oai_citation:4‡Ready
Once inside, seal it:
- Close all doors, windows, vents, and shut down HVAC if possible.
- An interior room, especially in a damaged building—even with some debris risk—is much safer than exposure outside.
oai_citation:5‡Florida Disaster oai_citation:6‡Science News
Fallout & Sheltering: You Have a Short Window (~15 Min On)
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If you’re >1 mile from ground zero, expect fallout to begin≈10–20 minutes after the blast, settling rapidly afterward.
oai_citation:7‡SCP NRC -
Shelter immediately—the best protection is simply beneath a large mass of building material or earth (ideally ~3 ft concrete or packed soil gives good gamma shielding).
oai_citation:8‡Wikipedia oai_citation:9‡Wikipedia -
Stay sheltered for at least 24–48 hours (authorities may advise up to 72h), allowing the most dangerous radiation to decay.
oai_citation:10‡FEMA oai_citation:11‡FEMA
Decontamination (as soon as you’re sheltered)
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Remove all outer clothing—this removes up to 90% of external fallout dust; seal it in a plastic bag away from living areas.
oai_citation:12‡U.S. Department of Homeland Security -
Gently wash exposed skin and hair using soap and shampoo—do not use conditioner, as it binds radioactive particles.
oai_citation:13‡U.S. Department of Homeland Security -
Do not leave to retrieve others until authorities confirm it’s safe; moving after fallout begins increases your exposure risk dramatically.
Potassium Iodide (KI): When & If You’re Asked
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Only take KI if and when it’s officially advised—it protects the thyroid against radioactive iodine (I‑131) only.
oai_citation:14‡Science News -
Recommended mainly for those under 40, pregnant, or breastfeeding; adults over 40 receive little/no benefit and may face more side effects.
oai_citation:15‡CDC oai_citation:16‡CDC
Understanding Radiation Decay: The “7‑10 Rule”
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For every 7-fold increase in time, radiation levels drop by 10-fold.
- After 7 hours → ~10 %
- After 49 hours (≈2 days) → ~1 %
- After 343 hours (≈14 days) → ~0.1 %
oai_citation:17‡Center for Domestic Preparedness oai_citation:18‡Atomic Archive
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Staying indoors as decay happens—especially >24 hours—is critical to minimizing dose over time.
Action Flowchart (formatted safely for Markdown parsers)
Timeline Table
| Time After Blast | Main Hazard | What to Do |
|---|---|---|
| 0 sec | Blinding flash | Turn away → drop flat → cover eyes |
| < 1 min | Thermal pulse & shock wave | Stay prone, shield exposed skin |
| 1–5 min | Blast damage & debris | Move to/from shelter based on location |
| 10–15 min | Fallout begins | Seal shelter, remove clothing, decontaminate |
| 15 min – 24 h | Peak radiation | Stay inside, minimal movement |
| 24–72 h | Radiation decays rapidly | Continue sheltering until official clearance |
What to Prepare Now
- Identify your safest shelters at home/work: basement, inner room, or thick staircase well.
- Assemble a kit including:
- Water (1+ gallon/person/day), non‑perishable snacks
- Battery or crank-powered radio, flashlight, extra batteries
- Soap, shampoo (no conditioner), plastic bags
- Masks, whistle, snacks, any emergency meds
- Know how alerts come: WEA, EAS, local radio, etc.—understand the alerts for “shelter in place”, “KI advised”, or “evacuate now”.
Why These Actions Save Lives
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Seconds save seconds: ducking and shielding even briefly cuts serious burn and blast injuries.
oai_citation:19‡Science News oai_citation:20‡Wikipedia oai_citation:21‡Florida Disaster oai_citation:22‡Wikipedia oai_citation:23‡Fallout Wiki -
Shelter matters more than panic: mass sheltered by any multi‑foot wall or flooring can reduce gamma exposure by 10–100×.
oai_citation:24‡Wikipedia -
Decontamination is surprisingly effective: removing outer clothing removes ≈90 % of radioactive particles.
oai_citation:25‡CDC oai_citation:26‡CDC -
Time is your ally: radiation drops sharply in the first 48 hrs—stay shielded to let decay offer safety.
oai_citation:27‡U.S. Department of Homeland Security
Bottom-Line Survival Protocol
- Flash! → turn, drop, cover
- After blast → get inside the strongest nearby structure
- Seal it carefully → let fallout pass
- Decontaminate if you were exposed
- Stay sheltered for 24–72 hours
- Only evacuate when instructed, and only take KI if advised by officials
Remember: authorities may not issue evacuation orders immediately—but they will provide updates. Be ready. Be disciplined. Act fast. Your survival may hinge on what happens in the first few seconds.