me CRLR - 466 ff, - INTERIM COMPREHENSIVE REPORT ON THERMAL RADIATION ATTENUATION, BY OIL-FOG SMOKE SCREENS. Elmer H. Engquist, Charles W. Forsthoff, Benjamin Barnett, and J. J. Mahoney, 23 March 1955. CONFIDENTIAL, Formal Report he e the way neerthe n the well ose at (U) A summary of the theoretical investigation of the effectiveness of smoke by a six-flux resolution of the complex single particle scattering function is presented. Preliminary predictions of the effectiveness of smoke against a 20-KT atomic weapon are given. (U) Results are given of the laboratory tests, the nonatomic field tests using the sun and photoflash bombs as sources of thermal radiation, and the Overation UPSHOT-KNOTHOLE atomic weapons field test of smoke, Excellent agreement was obtained between these data and theoretical predictions when comparison was made on the basis of attenuation as a function of path-length~-concentration product of fog-oil smoke screens. The meteorological feasibility of establishing smoke screens over urban areas in the United States is reviewed. Adequate data are available to raxe a detailed analysis for smoke-screening purposes for 97 of the 106 cities with over 100,000 population. This study also shows that the feasitility for establishing adequate smoke screens is high, ranging fran 75% to 86% of the time at night, and 24% to 64% of the time during in the day, from line sources of generators. For an area array of smoke generators, the feasibility at the present time is estimated to exceed 90% of the tine at night. ered we An outline of the proposed logistics study of smoke screening with preliminary results is presented. For air-burst atomic weapons , D, 18 es a 1 sult. 4d detonated over smoke screens, an operational concentration smoke screen establishei in accordance with the generator spacings given in FM 3-50, should previde a reduction of thermal radiation to less than 3 cal/sq in. (U) Smoke screens are used to reduce thermal-radiation casualties to troops ani to prevent the initiation of fires and thus the development of mass fires in strategic targets. Information is presented on the visibility in smoke screens and the toxicity of fog-oil screens. Visi- bility is markedly dependent on meteorological conditions. Fog-oil smoke screens are nontoxic in all concentrations normally experienced in the field.