known.) Sampler aircraft were also pressurized and fitted with 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 sampling missions to reduce the possibility of inhaling radioactive particles. Certain temporary modifications to the task group ships were required to comply with the regulations set forth in the Radiological Safety Plan. In 1954, Navy ships were not normally equipped with a washdown system. Instead, ships ordered to support nuclear testing relied upon a temporary arrangement "of hoses and special nozzles, connected to the fire main system." Por the CASTLE operation, the equipment necessary to rig this ap- Paratus was supplied by the Navy Bureau of Ships (BuShips) and arrived in the PPG on board the Bairoko for installation aboard the ships ence ll, p. lla-1). (Refer- A BuShips representative assigned to the staff of TG 7.3 supervised the work on all ships except the fleet tug, USS Tawakoni, which reported "with a washdown system already installed by the ship's force from standard firefighting equipment” (Reference ll, p. lla-l). In addition to jts own washdown system, the Bairoko also carried a helicopter decontamination "bathtub" to be used by helicopters of HMR-362. The bathtub was a 60- by 20-foot (18.3- by 6.l-meter) canvas rectangle constructed of 20-ounce canvas, and was described by the TG 7.3 final report (Reference ll, p. lla-3) as follows: The tarpaulin was treated with canvas preservative for waterproofing. When the tarpaulin was in place aft of the 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 using a P-500 pump connected to fresh water mains below decks. The bathtub was equipped with two drains. The function of the bathtub 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 given a lecture on radiological safety, followed by an "atomic defense inspection." 121