Document o9Brevrn3dz9g5Z5Oy4x9BzmR

2 January 5 1971 R. B. Hayden week. An Insulator working under normal Insulation shop conditions would be exposed to much less average concen trations. The ACG7.H states "Tine-weighted averages permit excursions above the limit provided they are compensated by equivalent excursions below the limit during the work day". The statement in the report that the composition of the samples taken during sawing were the same as the samples taken after a settling period is significant in that we should not favor materials that visibly appear to have rapid settle out of dust after working them. An inquiry to all of the manufacturers of the materials we tested determined that the types of asbestos in the insulations was either amosite or chrysotile; none con tained any crocidolite, which is considered to be the least desirable. The percent of asbestos content of each of the insulationsi as advised by the manufacturers compared very closely to the amounts determined in our study. Specific recommendations have not been made because the insulations showing the least fiber count can be handled so carelessly that they can become the most hatardous. and conversely the ones showing the higher fiber counts can be handled so carefully- that they become the least hazardous. Since insulation shops and operations vary widely throughout the Company the insulation selection should be made to meet the specific site conditions. If I can be of further service to you, please contact me. ENGINEERING SERVICE DIVISION G. E. Lang, Consultant Materials Engineering GEL/cgs Attach. DUP 0901621