APPENDIX A DECONTAMINATION PROCEDURES AND RESPIRATORS USED AT LASL IN 1944 The following is an excerpt from a Secret letter written by L. H. Hempelmann to Dr. Robert S. Stone Clinton Laboratories, Knoxville, Tennessee, dated July 20, 1944, which describes decontamination procedt and respirators: Decontamination Procedures: A. Floors: A special corp of janitors assigned to these laboratories spend all their time on this job. They work under the supervision of a head janitor and a “laboratorian."' In order to get good results and to keep the floor counts low, it is necessary for the floors to be covered with a smooth hard surface of wax. There does not seem to be much difference in the kinds of wax that we used so we have settled on the water-soluble floor wax supplied by the janitor service. Our present floors are made up of some asphalt tiles known by the trade name of "Mastic." some new laboratories we plan to use a smooth asphalt surface with an MgO base. 1. In Routine Cleansing: All floors are mopped once a day; floors of hot laboratories are mopped twice a day or oftener. They are wet mopped with a good lather of Ivery soap, followed closely with a dry (wrung out) mop. It is essential that the janitors be meticulously careful about covering the entire floor. The results are better if the wash and rinsing water be kept separate. By this method it has been pos- sible to keep the floor counts in most labs below 100. In our "hottest" laboratories, the counts are always below 500. We are now using some detergents in an effort to obtain better results. 2. Decontamination after Spillage: This is done by a trained decontamination squad. The floor is first mopped with Ivory soap. The wax is then removed with boiling hot water, followed by kerosene and steel wool, The floor is then painted with two coats of any thick paint which will stick to the surface. Desk Tops of Laboratory Benches: Every working surface is covered with a smooth surface preferably glass. Porous surfaces are covered with enamel paint before they are used for work. If they are contaminated by accident, an effort is made to seal them in the material by painting rather than to remove the contaminated part of the desk top. In the case of the lab benches made of "Kemrock" (the ordinary black surface made by the Kewaunne Mfg. Co., Adrian, Mich.) the surface responds to ordinary methods of decontamination although it appears to be porous. The same company puts out a surface paint of the same material, called "Kemrock Wipe Coat," which can be used to paint over contaminated surfaces. 1. Routine Cleaning: Smooth surfaces can be quite successfully decontaminated by wiping with a clean cloth wet with spindle oil. An excess of oil is used and this is followed by a clean dry cloth. The secret of the successful use of this method is to change cloths very frequently. The surface count is usually reduced below 50 per minute by this method. 2. Decontamination after Spillage (or after contamination from droplets produced by evaporation): First wipe the surface with 1 N HC1 solution followed by dry rag, then clean with oiled rag as above. Hands: Before starting work, spread thin coating of spindle oil over both hands; this must be done very carefully. Decontaminate gloves before removing them; remove gloves using surgical technique so as not to touch outside surface with hands. Apply coat of West's Sulfo soap to hands, moisten with water and lather, rinse; repeat with Sulfo soap and finally wash with Ivory soap. 22