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

On February 5, 2026, the New START Treaty expired. That was the last remaining nuclear arms limitation agreement between the United States and Russia. The Bulletin of the Atomic Scientists moved the Doomsday Clock to 89 seconds to midnight in their 2026 statement, citing accelerating nuclear risk across multiple flashpoints. Japan and Saudi Arabia are now openly discussing independent nuclear deterrent programs.

None of this means a nuclear event is imminent. It means the structural guardrails that existed for decades are gone, and the margin for miscalculation has narrowed. Preparedness is about margins. This guide covers what actually works, what the government's own data says, and what you should have in place before you need it.

Understanding the Threat: Blast, Thermal, and Fallout

A nuclear detonation produces three distinct hazards, each with different timelines and countermeasures.

The blast wave from a 1-megaton surface burst causes complete destruction within a 1.7-mile radius, according to FEMA's Nuclear War Survival Skills reference material. Severe structural damage extends to roughly 4.7 miles. At this range, concrete buildings may survive but wood-frame structures will not.

Thermal radiation travels at the speed of light. A 1-megaton weapon produces third-degree burns at up to 8 miles from ground zero on a clear day, per data from the Defense Threat Reduction Agency (DTRA). Any opaque barrier between you and the fireball — a wall, a hill, even a car — reduces thermal injury significantly.

Fallout is the hazard that affects the largest area and the one you can most effectively prepare for. Radioactive particles from a ground burst rise into the atmosphere and begin falling downwind within 15 to 30 minutes. FEMA estimates that fallout from a single 1-megaton ground burst can contaminate an area of 1,000+ square miles, depending on wind speed and direction.

The decay rate follows the 7-10 rule: for every sevenfold increase in time after detonation, radiation intensity drops by a factor of 10. After 49 hours (7 x 7), radiation is 1/100th of its 1-hour level. After two weeks, it drops to 1/1,000th. This is the basis for all shelter-in-place timelines.

Shelter: The Single Most Important Variable

Your survival in a nuclear event outside the immediate blast zone depends almost entirely on the shielding between you and fallout particles. The relevant measurement is the Protection Factor (PF) — how much the shelter reduces your radiation exposure.

FEMA's guidelines in the Emergency Management Institute's IS-100 series recommend a minimum PF of 40 for public fallout shelters, meaning occupants receive 1/40th of the outside radiation dose.

Here is what different structures provide, based on FEMA and DTRA data:

• Open field: PF 1 (no protection)
• Wood-frame house, single story: PF 2-3
• Basement of a wood-frame house: PF 10-20
• Concrete block building, no windows: PF 20-40
• Basement of a concrete or brick building: PF 40-100
• Underground parking garage, middle levels: PF 100-200
• Purpose-built fallout shelter with 3+ feet of earth cover: PF 200-1,000

The takeaway: get underground or get behind mass. Every foot of packed earth between you and fallout particles cuts radiation exposure roughly in half. Three feet of earth provides a PF of approximately 200, according to the Nuclear War Survival Skills manual developed by Oak Ridge National Laboratory.

If your home has a basement, you can improve its PF significantly with preparation. Stack sandbags, earth-filled containers, or even books and water containers against above-grade walls and around the shelter area. A lean-to of doors or plywood covered with 18 inches of earth against a basement wall creates a viable expedient shelter.

The 72-Hour Shelter Supply List

FEMA's Ready.gov recommends a minimum 72-hour emergency supply kit, but nuclear fallout scenarios demand a 14-day shelter capability. The first 48 hours carry the highest radiation, and the two-week mark is where exposure drops to manageable levels for limited outdoor movement.

Water: 1 gallon per person per day minimum. For a family of four sheltering for 14 days, that is 56 gallons. The CDC confirms that sealed, commercially bottled water is safe even if fallout lands on the exterior of the container — the contamination does not penetrate sealed packaging. Store water in your shelter area, not where you would need to cross open ground to retrieve it.

Food: 14 days of shelf-stable, no-cook food per person. Canned goods, freeze-dried meals, protein bars, peanut butter. USDA guidance confirms that food inside sealed containers (cans, jars, sealed packages) is safe from radioactive contamination. Remove and discard outer packaging, then wipe containers with a damp cloth before opening.

Radiation monitoring: Without a dosimeter or rate meter, you are guessing. The Department of Homeland Security recommends KFM (Kearny Fallout Meter) as a buildable expedient instrument. Plans for the KFM are published in the public domain through Oak Ridge National Laboratory. The Deadnet USB includes the full Nuclear War Survival Skills manual by Cresson Kearny, which contains step-by-step KFM construction plans along with calibration procedures.

Additional shelter supplies:

• Battery or hand-crank NOAA weather radio (EAS alerts will broadcast shelter-in-place durations)
• Potassium iodide (KI) tablets — FDA-approved thyroid protection; 130mg adult dose within 24 hours of exposure, per CDC guidance
• Plastic sheeting and duct tape for sealing windows and ventilation gaps
• N95 or P100 respirator masks for any brief exposure outside shelter
• Flashlights and batteries (LED preferred, 100+ hours per set of batteries)
• 5-gallon bucket with heavy-duty bags and cat litter (sanitation)
• First aid kit with a 14-day supply of any prescription medications
• Copies of identification documents and emergency contacts

Planning Your Response: The First 30 Minutes

The time between warning and detonation — or between detonation and fallout arrival — determines your options. FEMA's National Warning System (NAWAS) and the Wireless Emergency Alert (WEA) system on cell phones provide notification, but the window may be as short as 15 minutes for an ICBM launch detected at boost phase, according to Congressional Research Service reports on missile defense timelines.

Your plan needs to account for where you are most often, not just where you live.

At home: Move to your basement shelter area immediately. Seal the space. Do not go outside to observe. Turn on your NOAA radio. Stay put for a minimum of 24 hours, ideally 48-72 hours before any brief outdoor excursion.

At work: Identify the lowest interior room with the fewest windows. Move to a basement if available. Large commercial buildings with concrete construction provide PF 20-100 depending on your position. The center of a large building, away from the roof and exterior walls, maximizes shielding.

In a vehicle: You have 15-30 minutes before fallout begins arriving if you are outside the blast zone. Drive crosswind (perpendicular to the wind direction) if possible. Get to the nearest substantial building — concrete, brick, or underground. A car provides a PF of approximately 2, which is not survivable for extended fallout exposure.

With children at school: Most school districts have shelter-in-place protocols. FEMA guidance is that parents should not attempt to retrieve children during active fallout. The school building provides better protection than a car, and travel through fallout increases everyone's exposure. Confirm your school district's emergency plan in advance.

Decontamination Procedures

If anyone in your group was outside during fallout, decontamination before entering the shelter is a strict requirement. Fallout particles behave like dust — they sit on surfaces and continue emitting radiation until removed.

The CDC's decontamination protocol:

1. Remove all outer clothing before entering the shelter. Bag it and leave it outside. This step alone removes approximately 90% of external contamination, per CDC data.
2. Shower or wash thoroughly with soap and water. Shampoo hair but do not use conditioner — it binds particles to hair.
3. Blow nose, wipe eyelids and ears with a clean damp cloth.
4. Put on clean clothing that was stored inside the shelter.

If water is limited, use wet wipes or damp cloths, working from head to feet. Any removal is better than no removal.

Communications During a Nuclear Event

Expect cellular networks to fail within minutes of an event, either from electromagnetic pulse (EMP) effects, infrastructure damage, or overload from call volume. The Federal Communications Commission (FCC) documented that cellular networks reached 100% capacity within 30 minutes of the September 11 attacks, and a nuclear event would exceed that load by orders of magnitude.

Your communications plan should not depend on cell phones.

• NOAA Weather Radio: Battery-powered, receives Emergency Alert System broadcasts. Operating frequency range is 162.400-162.550 MHz. This is your primary information source for fallout patterns, shelter duration, and evacuation orders.
• AM/FM radio: FEMA's Emergency Alert System uses commercial AM/FM stations as backup broadcast points. A hand-crank radio with AM/FM/NOAA is the minimum standard.
• FRS/GMRS two-way radios: For communication within your group at distances up to 2 miles in urban terrain. No license required for FRS; GMRS requires an FCC license but is not enforced during declared emergencies.
• Ham radio: If you hold a license, 2m/70cm handheld radios can reach local repeaters. HF capability (General class license) enables long-range communication when infrastructure is down.

Store all electronic communication devices in a Faraday bag or a sealed metal container (galvanized trash can with tight-fitting lid and aluminum tape on seams) to protect against EMP effects. An EMP from a high-altitude nuclear burst can damage unprotected electronics at distances of hundreds of miles from the detonation, per the Congressional EMP Commission's 2008 report.

Long-Term Considerations: Week Two and Beyond

After 14 days, outdoor radiation levels from initial fallout have dropped to approximately 1/1,000th of their 1-hour value. This does not mean the environment is safe — it means limited outdoor activity with protective measures becomes feasible.

Priorities shift to:

Water sourcing: Municipal water systems may be non-functional. Groundwater sources (wells) are generally protected from fallout contamination, according to EPA guidance, because soil filters particulates effectively. Surface water (rivers, ponds) should be treated as contaminated. Standard filtration removes particulate fallout, followed by purification for biological contaminants.

Food security: USDA estimates that the average American household has 3-7 days of food on hand. After your shelter supplies are consumed, you need a resupply plan. Food in sealed containers inside undamaged buildings is safe. Gardens and crops exposed to fallout should not be consumed until tested or until sufficient time has passed for short-lived isotopes to decay.

Medical care: Hospitals within affected areas will be overwhelmed or non-functional. The Department of Health and Human Services' Radiation Emergency Medical Management (REMM) guidelines are available as a free download and cover triage, treatment of radiation injuries, and management of combined injuries. The Deadnet USB carries several military medical field manuals that cover trauma treatment and triage procedures applicable when professional medical care is unavailable.

Community coordination: FEMA's Community Emergency Response Team (CERT) framework provides the organizational structure for neighborhood-level response. The single most effective post-event action is connecting with neighbors to pool resources, share information, and coordinate security. FEMA data from Hurricane Katrina shows that 77% of initial rescues were performed by neighbors and bystanders, not professional responders.

What You Can Do Today

Do not try to build a complete nuclear preparedness system in one weekend. Start with the action that gives you the highest return for the least effort, then build from there.

This week, do one thing: fill clean containers with 14 gallons of water per person in your household and store them in your basement or lowest interior room. That is 14 days at 1 gallon per person per day. Use clean 2-liter soda bottles, water jugs, or purpose-built water storage containers. Treat with 1/8 teaspoon of unscented household bleach per gallon if storing tap water for more than 6 months, per EPA water storage guidelines.

Once the water is stored, your next step is a NOAA weather radio and a supply of KI tablets. Then work through the shelter supply list above, one category at a time.

The information matters as much as the supplies. Knowing the 7-10 rule, understanding protection factors, and having decontamination procedures committed to memory costs nothing and could be the difference between a recoverable dose and a lethal one. Print this guide. Store a copy with your supplies. If you want a broader reference library that works without power or internet — including the full Nuclear War Survival Skills manual, military field manuals, and medical references — that is what the Deadnet USB was built for.

Start with the water. Everything else follows.