Radiation fallout deteriorates to 1/2 life within 2 weeks. So anything past a month coming down would not be all that harmful.
Another item that will be useful is personal radiation dosimeter. It stores in your pocket and tracks cumulative levels of radiation. I bought some last year and they have already gone up 45%!
From Canadian Prepper’s latest video. Possible nuke strikes.
View attachment 17623
More likely nuke strikes. He doesn’t think they would do more than this…at least at first.
View attachment 17624
Depends on the type of radioactive isotope as to how long it will be until you can let your guard down and breathe easy that you dodged the bullet so to speak.
If the bomb that hit contains Strontium 90 which is common in nukes, it's half life is 29 years. So it might be a while before the "all clear" is assured. Strontium 90 also morphs creating other compounds.
The heavier radioactive particles will drop to the ground first, closest to the detonation site. The lighter ones can float for years. There are over 300 different fission products that may result from a fission reaction
"After an air burst the fission products, unfissioned nuclear material, and weapon residues which have been vaporized by the heat of the fireball will condense into a fine suspension of very small particles 0.01 to 20 micrometers in diameter. These particles may be quickly drawn up into the stratosphere, particularly so if the explosive yield exceeds 10 Kt. They will then be dispersed by atmospheric winds and will gradually settle to the earth's surface after weeks, months, and even years as worldwide fallout. The radiobiological hazard of worldwide fallout is essentially a long-term one due to the potential accumulation of long-lived radioisotopes, such as strontium-90 and cesium-137, in the body as a result of ingestion of foods which had incorporated these radioactive materials. This hazard is much less serious than those which are associated with local fallout and, therefore, is not discussed at length in this publication. Local fallout is of much greater immediate operational concern."
Nuclear Weapon Radiation Effects
I am loathe to believe the information that the government puts out there regarding how long you should shelter in place. They are much more motivated by Continuance of Government, AKA maintaining control than they are concerned with our health and the panic truth might cause.
They have their bunkers all nicely prepared, to go for a year or more. Should tell us something about the reality of the situation.
Uranium
Uranium is the prototypical radioactive element, and the isotopes uranium-235 and uranium-238 are used in nuclear reactors. These isotopes have a half-life of 4.46 billion years, and 704 million years, respectively, making them some of the longest lived sources of radioactivity.
Plutonium-239
When uranium-238 in nuclear reactors is exposed to neutron radiation, it can form plutonium-239, which is used in nuclear weapons. This radioactive isotope has a half-life of 24100 years and decays into uranium-235.
Strontium-90
Strontium-90 is another component of nuclear reactor waste, and has also been spread throughout the world by nuclear weapon testing. This isotope has a half-life of 29.1 years, and can form many different radioactive compounds in the environment.
Caesium
Radioactive waste also contains caesium-135 and caesium-137. These isotopes have a half-life of 2.3 million years, and 30.17 years. Like strontium-90, they can form many different compounds in the environment, and are thus hard to remove.
