dhi ee D. * E, re me oe < = Sr90 Air Concentration, Port Lyautey, Morocco 61 Sample Number Collection Period Sr90/106ft3 CL 206B July 9-11, 1953 9.70 x 0.45 CL 206C July 11-13, 1953 38.6 + 1,2 CL 206D. July 13-16, 1953 CL 206A Sept. 30-Oct. 1, 1953 20.1 + 0.6 CL 2068 Nov, 2-9, 1953 8.10 + 0.22 CL 05-P Nove. 8-9, 195) 155 + 1h CL h06-P Dece 3-4, 195) 214 + 20 CL 416-P Jan. 4-6, 1955 58.1 + 10.0 CL 530-P Feb. 28-Mar. 2, 1955 552 + 110 CL 531-P March 6-8, 1955 430 + 60 CL 532-P March 16-18, 1955 313 + ho CL 533-P March 22-21, 1955 119 + 25 ; 8.70 * 0.33 Multivie Filters Multiple filter collections were made by the Naval: Research. Labora~ tory, Washington, D.C., using a set of three filters in series, with flow rat maintained at 20°CFM, The two week coliection volume is 4.0 x 10 cubic feet, The top filter, changed daily, is a viscose filter which gives 75% penetration of 1.0 » particles and 85% penetration of 0.3 p particles at this flow rate. The middle filter, also viscose, gives 25 and 50 percent penetration of 1.0n and 0.3 p particles, respectively. The bottom filter is Army Chemical Corps Type 7 (asbestos filter) of very nearly 100% retention. Table IV MULTIPLE FILTER DATA Sample Number - Filter . CL 539-P Top - Mult, #1&2 CL 50-P Middle Collection Period 1/31/55-2/1h/55 Comb, No. D.P.M. Sr9O % of sr90 of Papers Total Frac. Activity 1b/l ad 23.0 + 1.5 4h.0 * " a, n 2/lwk 13.9 + 1.2 26.6 CL 51-P Bottom " " " " 2/ltk 15.4 + 1.0 290k U/ld 37.2 + 2.1 5149. ARCHIVES CL 542-P Top — Mult. #3&, 2/14/55-2/28/55 CL 5)3-P Middle " . © " " ‘2/lwk =612.8 + 0.8 17.8 CL Suu-P Bottom " 1 fn n _O/lwk 21674 2h 3043 137