"A survivor in a shelter that does not have a dependable meter to measure fallout radiation or that has one but lacks someone who knows how to use it will face a prolonged nightmare of uncertainties. Human beings cannot feel, smell,
taste, hear, or see fallout radiation. A heavy attack would put most radio stations off the air, due to the effects of electromagnetic pulse, blast, fire, or fallout from explosions. Because fallout intensities often vary greatly over short distances, those stations still broadcasting would rarely be able to give reliable information concerning the constantly changing radiation dangers around a survivor's shelter.
"Which parts of the shelter give the best protection? How large is the radiation dose being received by each person? When is it safe to leave the shelter for a few minutes? When can one leave for an hour's walk to get desperately needed water? As the fallout continues to decay, how long can one safely work each day outside the shelter? When can the shelter be left for good? Only an accurate, dependable fallout meter will enable survivors to answer these life-or-death questions.
"The National Academy of Sciences' Advisory Committee on Civil Defense in 1953 concluded: "The final effectiveness of shelter depends upon the occupants of any shelter having simple, rugged, and reliable dose rate meters to measure the fallout dose rate outside the shelter."
Read WARNINGS FOR BUYERS OF FALLOUT METERS before you buy a meter.
It's relatively inexpensive to make your own. Read A HOMEMAKEABLE DOSE RATE METER, THE KFM.