Tne open-close total collector (occ) 27 was designed to collect and hold fallout material wnile reducing to a minimum tne amount of extraneous material deposited both before and after the collecting period. Wnen triggered either by an increase in radioactive backsround or by hand, the cover of the device opens and a collecting tray rises into the wind stream for the preset exposure time in 15-minute increments between O and 81 hours). (variable The tray has an effective collecting area of about 2.5 square feet divided into numerous cells to reduce loss of material due to wind, Samples, other than cloud samples, were obtained from this type of collector mounted on converted liberty shivs (12G's), barges (YFNB's) and ‘How Island. fee -} After collection the fallout material was flown back to the Laboratory and aliquoted by Chemical Technology Division. The aliouots susplisd to this section for analy- Sis were placed in the polystyrene containers and prevented from shifting, in the case of cranular or pulverized samples, by tne addition of a small amount of paraffin. The machine was calibrated so that on "standard" gain the total absorption peak of a 100, 200, or 300, etc., kev gamma ray would be centered on the 1/2-inch, l-inch, or 1-1/2inch, etc., line on the recordine paper. This calibration was accomplished first by careful zero-settins of the X-Y 8