decontamination. It is difficult to believe but, ience of the because of the bulkiness and inconven techearly so-called portable counters, the swipe nique of monitoring was continued in some labSimilarly, in the oratories until June 1945. absence of air samplers for radioactive dusts (the first became available in the fall of 1944), both nostrils of each plutonium worker were "swiped" routinely with rolied moistened strips of filter paper at the end of the working day or if accidental pulmonary exposure was suspected. These samples were also counted in a stationary alpha particle counter. If the nose swipe exceeded 50 counts per minute, the subject was questioned carefully about possible accidental inhalation or breakage of safety regulations (e.g., hand contamination of the nostriis). In April 1945, kilogram quantities of plutonium from the newly operating Hanford piles began to arrive at Los Alamos for processing and fabrication into the first atomic bombs. ee ak time portable alpha counters Fig. 2. Fortunately, by this (Fig. 2) and contin- uously operating air samplers were available toa A semi-portable alpha counter called "Supersnacp” used in early 1945. urine assay method for plutonium’ had been developed; this allowed crude estimates of the body burdens of help with monitoring for contamination of certain plutonium to be made (not including insoluble com- laboratories. pounds in the lung). Operating equipment, including air However, even with improvements lines in some laboratories and specially made positive-pressure masks, also had been improved. Although most procedures were carried out in dryboxes, some work had to be done in open hoods (Fig. 3). This was particularly true in the case of the Recovery Group, the activities of which were so diverse and unstandardized that closed systems were totally inoperable.» Also by March 1945, a RKK The swipe technique measured only alpha particleemitting materials not fixed to the surface. Oil on the filter paper used for surface swipes probably decreased somewhat the measurable alpha activity. The moistened paper strips used for nose counts were dried before counting; consequently, the measured activity was probably more accurate than that of the oiled swipes. The geometry of the stationary Proportional counter was relatively good, approach- ing 50 percent. In contrast to poorly fixed radio~ ° activity measured by the swipe technique, portable counters developed later measured fixed as well as unfixed radioactive contamination with a rather poor geometry (10 to 15 percent). kk The nose counts and air counts (at woke; first one sampler in the most hazardous laborator y) were by no means accurate measures of exposure of personnel. At best, they were merely crude indications that permissible contamination levels had been exceeded or that safety regulations might have been violated. Fig. 3. One of the steps in the purification operation performed in an open chemical hood. The operator is wearing the standard protective clothing and respirator (Wilson 750).