known.) Sampler aircraft were also pressurized and fitted wiffh a special filter to prevent the entry of radioactive particles. All TG]7.4 crew- members were required to breathe 100 percent oxygen during and after samp- ling missions to reduce the possibility of inhaling radioacti Particles. Certain temporary modifications to the task group ships were required to comply with the regulations set forth in the Radiological fety Plan. In 1954, Navy ships were not normally equipped with a washdownl system. Instead, ships ordered to support nuclear testing relied upon temporary arrangement "of hoses and special nozzles, connected to the fife main sys- tem." For the CASTLE operation, the equipment necessary to rig paratus was supplied by the Navy Bureau of Ships (BuShips) this ap- andJarrived in the PPG on board the Bairoko for installation aboard the ships (Reference ll, p. lia-l). A BuShips representative assigned to the TG 7.3 supervised the work on all ships except the fleet tug, taff of SS Tawakoni, which reported "with a washdown system already installed by th ship's force from standard firefighting equipment" (Reference il, p. a-1). In addition to its own washdown system, the Bairoko also c ried a helicopter decontamination "bathtub" to be used by helicopters The bathtub was a 60- by 20-foot (18.3- by 6.l-meter) canvas r tangle constructed of 20-ounce canvas, and was described by the TG 7.3] final report (Reference 1l, p. lla-3) as follows: The tarpaulin was treated with canvas preservative for waterproofing. When the tarpaulin was in place aft of fhe elevator the sides were raised by use of stanchions and wire cable to form a so-called "bathtub." Fresh water under pressure was provided on the flight deck by usingfa P-500 pump connected to fresh water mains below decks. The bathtub was equipped with two drains. The function of the Wathtub was to collect the wash water and duct it directly over the side rather than spilling it on the flight deck. After installation of ship washdown systems, the crews were lecture on radiological safety, followed by an “atomic defense 121 piven a ihspection.”