Nuclear Preparedness Guide: What You Actually Need to Know and Do

The last nuclear arms control treaty between the United States and Russia — New START — expired on February 5, 2026. No replacement is in negotiation. Both nations are modernizing their arsenals. China is expanding its own. The Bulletin of the Atomic Scientists has kept the Doomsday Clock at 90 seconds to midnight, the closest it has ever been.

This is not a reason to panic. It is a reason to prepare. The physics of nuclear weapons are well understood. The protective measures are documented, tested, and straightforward. Most people who would die in a nuclear event outside the immediate blast zone would die from ignorance, not from inevitability.

This guide covers the actual science, the actual supplies, and the actual decisions you need to make — drawn from U.S. government and military planning documents that have been refined over decades of nuclear threat assessment.

Understanding What You Are Preparing For

A nuclear detonation produces three threat layers, each with a different timeline and different countermeasures.

The blast wave from a 1-megaton weapon (a common warhead yield in current arsenals) causes total destruction within roughly 1.7 miles of ground zero and severe structural damage out to about 4.7 miles. According to FEMA's Planning Guidance for Response to a Nuclear Detonation (2024 edition), the thermal pulse — the flash of heat — can cause third-degree burns at distances up to 5 miles for a weapon of this yield under clear conditions.

The initial nuclear radiation pulse is lethal within about 1.5 miles but drops off quickly with distance. This is not the primary threat for most people.

Fallout is the primary threat for the largest number of people. Radioactive debris is pulled up into the mushroom cloud and deposited downwind over hours and days. The fallout zone from a single ground-burst weapon can extend 100 miles or more downwind, depending on yield and weather. According to the Department of Homeland Security, the most dangerous fallout settles within the first 24 hours, and radiation intensity decreases by roughly 90% after 49 hours due to radioactive decay following the 7-10 rule: for every sevenfold increase in time after detonation, radiation intensity drops by a factor of 10.

This decay curve is what makes survival realistic. You do not need to stay sheltered for weeks. You need to stay sheltered for 48 to 72 hours to avoid the worst exposure, then make informed decisions about movement.

Shelter: The Single Most Important Variable

The difference between adequate shelter and no shelter during a fallout event is the difference between a survivable dose and a lethal one. FEMA's Nuclear Detonation Planning Guide estimates that sheltering in a large concrete or brick building reduces radiation exposure by a factor of 200 or more, meaning you would receive 1/200th of the outside dose. A typical wood-frame house provides a protection factor of only 2 to 4.

What to look for in a shelter:

• Concrete, brick, or earth-sheltered structures. Basements are ideal.
• The center of a large building, away from exterior walls and the roof. Each floor above you adds shielding.
• Underground parking garages, subway stations, or commercial building basements are excellent improvised shelters.
• If you are in a wood-frame house, move to the basement. If there is no basement, move to an interior room on the lowest floor.

The key metric is mass between you and the outside. Every 2.2 pounds per square foot of material between you and the fallout particles reduces your gamma radiation exposure. Concrete walls, packed earth, even books and water containers stacked against walls add meaningful shielding.

If you have the resources to prepare a dedicated shelter space in advance, focus on one room — ideally a basement or interior room — and pre-position your supplies there. Seal windows and doors with plastic sheeting and duct tape to reduce dust infiltration. This is not about creating an airtight space. It is about reducing the amount of radioactive particulate that enters your breathing zone.

The Supply List That Actually Matters

Most nuclear preparedness lists circulate the same generic items. Here is what specifically matters for a nuclear event, and why.

Water: FEMA recommends one gallon per person per day. For a 72-hour shelter-in-place, that means a minimum of 3 gallons per person. Store at least 7 gallons per person to account for hygiene and decontamination needs. Sealed containers kept away from potential blast areas are preferable to tap water, which may become contaminated if infrastructure is damaged.

Potassium Iodide (KI): The FDA has approved potassium iodide as a thyroid blocking agent against radioactive iodine-131, a common fission product. The adult dose is 130 mg, taken once daily for up to 14 days after exposure. KI only protects the thyroid — it does not protect against external gamma radiation or other isotopes. The CDC reports that thyroid cancer is the most common cancer resulting from nuclear fallout exposure, particularly in children, making KI a high-priority supply item for families.

Dosimeter or Rate Meter: Without a radiation measurement device, you are guessing when it is safe to leave shelter. Civil defense surplus dosimeters (CDV-742 models) can still be found. Modern options include the RADTriage personal dosimeter card (about $25) which gives a cumulative dose reading using a color-change indicator. Knowing your accumulated dose in roentgens or rem is the difference between an informed evacuation and a blind one.

Battery-Powered Radio: NOAA Weather Radio and the Emergency Alert System will broadcast fallout patterns, safe evacuation routes, and dose-rate data. A hand-crank radio with AM/FM/NOAA bands removes battery dependency.

Plastic Sheeting and Duct Tape: 6-mil polyethylene sheeting for sealing windows, doors, and vents. Pre-cut the sheeting to your window sizes and label each piece. During an actual event, you may have 15 to 30 minutes to shelter and seal.

N95 or P100 Respirators: Fallout particles are physical debris, not a gas. A properly fitted N95 mask filters 95% of airborne particulate according to NIOSH standards. P100 filters catch 99.97%. This prevents inhalation of radioactive dust, which causes internal contamination — a far more dangerous exposure pathway than external radiation at moderate distances.

Food: Sealed, shelf-stable food that requires no cooking. Cooking means ventilation, and ventilation during the first 48 hours means pulling contaminated air into your shelter. Canned goods, MREs, protein bars, and peanut butter are all adequate. Aim for 2,000 calories per person per day minimum.

Decontamination Procedures

If anyone in your group was outdoors during fallout, decontamination before entering the shelter is a priority. According to the Department of Homeland Security's Improvised Nuclear Device Response Guide, removing outer clothing eliminates approximately 90% of external radioactive contamination.

The procedure:

1. Remove all outer clothing before entering the shelter. Place it in a sealed plastic bag and leave it outside.
2. Shower or wash exposed skin with soap and warm water. Do not scrub aggressively — intact skin is an effective barrier, and abrasions create pathways for contamination.
3. Shampoo hair thoroughly. Hair traps particulate effectively.
4. Blow nose, wipe eyelids and ears with a damp cloth.
5. If water is limited, use wet wipes on all exposed skin.
6. Put on clean clothing.

Do not use conditioner on hair after potential fallout exposure. Conditioner binds particles to hair rather than releasing them.

The 72-Hour Decision Cycle

The first 72 hours follow a predictable pattern based on the 7-10 decay rule.

Hours 0-2: Get inside the best available shelter. If you saw the flash, do not look toward it — retinal burns can occur at distances where no other injury would happen. Move immediately to your shelter location. You have roughly 15 to 30 minutes before fallout begins arriving, depending on your distance from the detonation and wind speed.

Hours 2-24: Stay sheltered. This is the period of highest radiation intensity. According to the EPA's Protective Action Guides, the dose rate at 1 hour after detonation will be approximately 10 times higher than at 7 hours and 100 times higher than at 49 hours. Do not go outside for any reason during this window unless your structure is on fire or collapsing.

Hours 24-48: Radiation levels have dropped significantly but remain hazardous. Monitor radio broadcasts for official dose-rate readings in your area. If you have a dosimeter, take a reading. Continue sheltering.

Hours 48-72: Radiation has decayed to roughly 1% of its 1-hour intensity. This is the decision point: continue sheltering, or evacuate if directed. If your shelter is inadequate or supplies are running low, this is the lowest-risk window for movement.

After 72 hours: Follow official guidance. If communications are down, the general rule is to move perpendicular to the downwind fallout path — not directly upwind or downwind. FEMA guidance notes that fallout patterns are elongated ovals aligned with the wind direction at the time of detonation.

Communication and Information After Detonation

A nuclear detonation — especially a high-altitude burst — can generate an electromagnetic pulse (EMP) that damages or destroys unshielded electronics within line of sight. Even a ground-burst weapon will disrupt communications infrastructure in the affected area. Cell towers, internet service, and landline phone systems may all be offline.

Your information sources, in order of reliability:

1. NOAA Weather Radio (162.400-162.550 MHz) — hardened transmitters, wide coverage
2. AM radio — long-range propagation, especially at night
3. Shortwave radio — if you have a receiver, international broadcasts will carry information even if domestic infrastructure is degraded
4. Community word of mouth — unreliable but sometimes the only option

Pre-loading reference material on a device that does not depend on the internet or the grid is a force multiplier here. The Deadnet USB drive contains the full text of key military nuclear survival references — including FM 3-11 (Chemical, Biological, Radiological, and Nuclear Operations) and FEMA's nuclear response planning documents — accessible on any laptop without power grid, cell service, or internet connectivity. Combined with the onboard AI assistant, you can query specific decontamination procedures or dose-rate calculations without flipping through hundreds of pages under stress.

Common Misconceptions That Get People Killed

Misconception: A nuclear attack means everyone dies. Reality: A single weapon detonated over a city would kill tens of thousands in the immediate blast zone. But the majority of people within the broader affected area — the fallout zone — can survive with proper sheltering. The Congressional Research Service estimates that adequate shelter-in-place for 48 hours could reduce casualties in the fallout zone by 50 to 70%.

Misconception: You need a bunker. Reality: The basement of a typical commercial building provides a protection factor of 100 to 200. A residential basement with earth berming provides 20 to 100. You do not need a purpose-built bunker. You need to know where the nearest high-mass structure is.

Misconception: Potassium iodide protects against all radiation. Reality: KI blocks radioactive iodine absorption by the thyroid gland. That is all. It does nothing against gamma radiation, beta burns, or ingested cesium-137. It is one tool, not a solution.

Misconception: If you see a mushroom cloud, it is too late. Reality: If you can see the cloud and you are still standing, you are outside the lethal blast radius. You have minutes, not seconds, to reach shelter before fallout arrives. Those minutes determine whether you survive the next 72 hours.

Building Your Nuclear Preparedness Kit

A focused nuclear preparedness kit stored in your shelter location:

• 7 gallons of water per person
• 72 hours of no-cook food (2,000 cal/person/day)
• Potassium iodide tablets (FDA-approved, check expiration annually)
• N95 or P100 respirators, 2 per person minimum
• 6-mil plastic sheeting, pre-cut to window and door dimensions
• 3 rolls of duct tape
• Battery-powered NOAA/AM/FM radio with extra batteries
• Personal dosimeter (RADTriage card or surplus CDV-742)
• Flashlights and batteries (stored in a Faraday-shielded container as EMP precaution)
• First aid kit with burn treatment supplies (silver sulfadiazine cream, sterile gauze)
• Wet wipes and contractor-grade trash bags for decontamination
• Change of clothes per person, sealed in plastic bags
• Printed reference material or an offline device with nuclear survival documents — the Deadnet USB drive is purpose-built for this scenario, containing 19 military and government source documents queryable without internet access

Keep everything in a single container in your shelter location. A large plastic tote works. Label it. Tell your household members where it is.

What to Do This Week

Do not let this guide become something you read and forget. Take one action today:

Walk to the nearest large concrete or brick building within 15 minutes of your home or workplace. Stand in the basement or the center of the lowest floor. That is your fallout shelter. Note the address. Tell your family. If you do nothing else on this list, knowing where to go when you have 15 minutes to act is the single highest-return preparedness step you can take, according to FEMA's own modeling — and it costs nothing.