of 20r measured gamma only. A one~time dosage of 25r is cur- rently used in civil defense concepts of operations but is not applicable as a general guide in Ivy unless as an accident. However, no one is expected to be exposed to radiation rates approaching 4r/hr. If such levels as these should be experienced on the islands of Eniwetok and Parry, a level of 4r/hr after 10 hours does not actually decay very rapidly according to calculations for such delayed fall out. However, from actual field ex- perience, it has been found that weathering (i.e., wind, rain showers, etc.) of such fall out on the ground reduces the levels by more than 50 ver cent in one day o2 according to tables: 10 hours,4r; 20 hours, 2r; 40 hours, lr; and 80 hours, 0.5r. Little will be gained by covering large regular objects since when the re-entry can be attempted for persons, levels of radiaticn on the equipment will in general be low. However, where equipment oper. to airborne contamination is complex, such as radio consoles, power control banks, or motor generators, fall out cone tamination can be materially reduced from collecting in such inaccessible spots by some covering. Hoods, when closed, on vehicle engines should suffice to reduce oily, greasy surfaces from collecting and holding contamination after all other surrounding areas have weathered down to insignificant levels. In general, the group recommended that common sense rules should govern in trying to reduce man hours tobe spent in decon~~