Science: Fall-Out Filter

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In an H-bomb attack, U.S. cities as far as 190 miles away from the actual explosion could expect a deadly fallout of wind-borne radioactive particles (TIME, Feb. 28). Last week in Madison, Wis., the U.S. Forest Products Laboratory described a new building material called "diffusion board," that can protect against direct contact with radioactive dust.

Developed for the Army Chemical Corps, diffusion board resembles ordinary wood-pulp fiberboard, ⅝ in. thick. Impregnated with special chemicals (the kinds are still classified), it acts much like an ordinary Army gas mask, filters out gases and germ-carrying particles as well as radioactive dust, lets oxygen and carbon dioxide breathe through. Against direct radiation itself, the porous diffusion board gives no protection. Thick lead or concrete shields must be used to keep out death-dealing gamma rays. Moreover, lining the walls of an average home with the board would not eliminate dust, which could sift in over windowsills and door-jambs. But used in windowless shelters in fallout zones, the diffusion board can shield civilians and military personnel from inhaling or touching radioactive dust, keep vital defense centers going that otherwise would have to be evacuated.