Document 7MVazyQQg28NvY113XkXLQmO8

Abt Associates, Inc. -3- December 28, 1977 Page 37 The draft states that the first operation in brake maintenance shops which Is "known to produce dangerous levels of asbestos dust in the alt" is "blowing out brake drums with compressed air. This Is the chief hazard In automobile brake shops." There Is a question as to whether the decomposition products of used brake linings are the chief hazards in automobile brake shops. While this may be the case, I do not believe that it has been established that dust from the decomposition products of brake linings blown out with compressed air is the dangerous form of asbestos dust in the workplace. It Is more likely that grind ing, chamfering, drilling and cutting of new brake materials may be a more serious problem as regards producing respirable asbestos dust which would be the known dangerous asbestos product in the workplace. Further the draft indicates that other dangerous operations are the grinding of used truck brake linings and the beveling of new truck hrake linings. These 1 questionable conclusions from a non-typical shop are apparently the result of relying on the Rohl report of operations in a truck shop. My observation is that very few automobile brake shops bevel (or chamfer) new truck brake linings. Most do not even work on truck brake linings. There may be more problems with grinding drilling and chamfering (bevelling) operations In a shop which feels that they have to adapt materials to fit particular brakes. As indicated most lined brake shoes are usually ready fox installation without additional machining, and this p rocedure should be recommended. It might also be commented that with the author's emphasis on blowing out of brake drums and grinding and bevelling brake linings, and with Illustrations always showing drum brake linings, that the new and now common disc brake linings have not been mentioned. Obviously disc brake linings are widely used and are on over 50% of the brakes on new cars today. The only drum brake linings are on the rears. In many cases these drum brake linings are not relined as often as the disc brake linings. I agree that blowing out brake drums with compressed air is not a good practice and should be discontinued. I do not believe that it has been established that this is the chief hazard in automobile brake shops. The wording should refer toblowing out "brakes" with compressed air. Most times the mechanics take the air hose directly over to the vehicle with disc or drum brakes and blew out the dust from around the caliper or cylinders before proceeding with the reline. (This is indicated in slide 12). I believe that illustrations and comments should be made of disc brakes as well as drum brakes so that this guide will not be considered a publication of the 1960's. Pages 32, 34. 36. 64 Illustrations on these pages show a technician taking a sample of asbestos holding a probe or collector. Samples are not taken in this fashion. A sample is norm ally taken with the worker wearing the sample collector in a fashion that would be equivalant to his breathing the air at hia work station. SPNY 004742