What are typical safe-distance guidelines (in km or miles) for different damage thresholds from a 1 Mt airburst?

1. Why a single "safe distance" is misleading — the technical caveats

National Academies analysis stresses that yield, weapon design, height of burst (HOB), surface type and weather all change how much dust/fallout and blast effects occur, so any flat distance rule is inherently incomplete; an airburst at the "fallout‑free" HOB produces far less local fallout than a surface burst ^[1]. That same study explains that the mass of surface material entrained into the cloud is a major determinant for fallout; a surface burst typically generates about three times the dust mass of a low‑airburst, and the resulting radiation hazard at distance will therefore differ strongly ^[1].

2. Blast and overpressure distances — ranges rather than single points

Technical and modeling discussions (and tools such as NUKEMAP discussed in the nuclear history blog) show blast and thermal effects are best expressed as concentric damage rings that extend for miles for multi‑megaton yields; the blog notes airburst modeling becomes complex for large yields and that thermal/blast extrapolations can be unreliable outside validated ranges ^[3]. The crowd/technical thread cited in search results shows people using psi thresholds (e.g., 6 psi linked to very high fatality) to estimate mile‑scale distances for a 1 Mt airburst, but that is a community estimate rather than an official standard and varies with burst height ^[4].

3. Fallout and "safe distance" for radiation — wind matters

Practical safety guidance aimed at the public emphasizes distance plus sheltering: an FAQ‑style source suggests that being ~50 miles away "offers better protection" from fallout in many scenarios but also warns fallout can travel farther depending on winds and weapon type ^[2]. That guidance illustrates the core point: distance reduces acute blast/thermal risk (which drop off rapidly with range), but long‑range radioactive contamination is governed by atmospheric transport and can move tens to hundreds of miles under some meteorological conditions — the National Academies material explains why airburst vs. surface burst is crucial to how much material becomes locally concentrated versus widely dispersed ^[1].

4. Official safety regimes use "quantity‑distance" logic, not single blast maps

Explosives‑safety frameworks such as DoD/DESR and civilian quantity‑distance tables treat explosive hazard as a function of energetic mass and exposure risk levels rather than offering a universal public "X miles is safe" rule; Wikipedia's explosives safety summary explains QD relationships define acceptable risk levels but do not provide absolute protection distances ^[5]. Military or range documents (global security example) focus on airspace and operational safety zones rather than civilian shelter recommendations ^[6].

5. Popular summaries, modeling tools and their limits

Journalistic and explainer pieces update visualizations and videos to show concentric damage zones; they are useful to illustrate scale (miles vs. kilometers) but rely on assumptions about HOB and environment. The Restricted Data blog discusses limits in modeling thermal ranges for very large yields and flags when extrapolations become unreliable — highlighting that public‑facing distances must be read with caution ^[3]. Science/press pieces similarly update but do not replace technical guidance ^[7].

6. Practical takeaway for readers seeking numeric guidance

Available sources do not provide a single authoritative table converting 1 Mt damage thresholds to exact km/mile distances for all effects; instead, they indicate: (a) blast/thermal lethal zones for a 1 Mt airburst are measured in miles (not tens or hundreds of miles for direct blast/thermal), (b) fallout risk depends on burst type and wind and can extend many tens of miles, and (c) professional safety frameworks use scenario‑specific modeling and quantity‑distance approaches rather than one‑size‑fits‑all rules ^{[4] [2] [1] [3] [5]}. If you need precise rings (e.g., 1 psi, 5 psi, thermal burn radii) for an exact HOB and surface type, consult a dedicated blast/fallout model or authoritative report — available sources here do not supply that full table directly ^{[3] [1]}.

Limitations and disagreements: the National Academies material is the closest authoritative technical discussion and emphasizes dependencies ^[1]; popular safety advice ^[2] gives simple distance guidance for lay readers, creating potential mismatch between professional modeling and consumer‑oriented rules of thumb ^{[2] [1] [3]}.