Document 0gQXBJ0VgmnZz6w3omXOO8Vod

ec: K. S. Freeman J. Valuer TO: . Jteynard FROM: Jhrv. Schmidt SUBJECT: Dust Hazard Due to Sanding The Joint Cement T.L.Y*s vere based on the following considerations. _v * 1. The undercoat calculates to about 11.2$ mica, 5$ asbestos and the retainer nuisance materials while the top coat calculates to 25$ mica, 5$ asbestdk and the remainder nuisance materials. Thus the top coat represents a more hazardous material than the under coat and vas used to determine the total T.L.V. - 2. According to P. Kipp the asbestos TLV has been officially lowered to 5 fibers per ml greater than 5 mu in length. Inasnuch as there is no .figure available for correcting this to an' "impinger value" but the 19&9 ACGH publications equates 2 mppcf to 12 fibers per ml, one can assume that there will be a proportionate reduction of the impinger count to 0.8 mppcf for 5 fibers per ml. Proa the above assumptions one can calculate the T.L.V. as being 10.8 The samples were taken in a room in Test Bouse C where the room was completely taped out and had no window. The air was relatively quiet. One sample holder vas mounted at the left shoulder of the sander while the other was set on a tripod in a corner of the room. It took 7 minutes to completely sand all joints so the sample vas collected for seven minutes at the rate of 0.1 cu ft per min. The samples were collected in Millipore filters and counted. The sample_(s?553) which was on the operators shoulder indicated.7.6 a.p.p.e.f. while the sample collected in the corner of the room (jr55^) showed 7*7 ra.p.p.c.f. According to the operator the amount of dust in the air was considerably higher, in his estimation, than normally encountered in sanding a Job. ~ Jrcm the above, ve can estimate that this joint cement, when handled in the usual way, does not present a hazard to the user. KS:ml 0 c