Document xd4qLDKZN7Ke4EZo435R1GGJ

FILE NAME: Mine Safety Appliances (MSA) DATE: 1971 Dec 8 DOC#: MSA005 DOCUMENT DESCRIPTION: Memo for File: Visit to McGill University Dust Respirator Program rineerino ter Lc O Q , D E C 1 0 19 MEMO EO VISIT TO McGIT.L VMI7EP.SITY OUST PI RAT OR PROGRAM C. Sheckler, J. E b y , R. Gresham, J. Matnescn of Wei sen Manu facturing Company, W. Burgess of Harvard Public Health ar. I met v i . . Prof. Barcswick and J. naj zero'./icr or: -cumber to revii ' their most recent report or. 3audio.- of aspi /ators for filtration of asbestos. Cliff Shock 1 v has -or.-.'Lete copy of this r.:oort. In general the technique is satisfactory as a means of comparison between respirators, although it differs from she standard uuruau of Mines certification procedure in flew rata, particular . con centration and other factors, including the use of asbestos rasher than silica dust. A secondary part of the procedure was she evaluation of leakage around the mask using a helium concentration technique. There is some question concerning the significance of these helium leakage tests, especially where the face seal is accomp_ished by h sponge rubber media. Filter penetration tests were run using a Byrd Mark 9 respirator operating at a total air volume of k liters/ minute and with fiber concentrations of approximately 2G, 10 , and 100 fibers/cc, respectively. Toe data indicate that the new 3M disposable filter, toe elsch disposacle filter and the Willson prototype filter wera all satis factory from a penetration standpoint. from a face leakage stand point the 3M and Welsch units were satisfactory, but m e Will sor. prototype showed excessive leakage. This will undoubtedly be less with the softer plastic to be used in the final material. By combining the fiber penetration through, leakage with the fiber penetration through the filter media, it was possible to calculate an anticipated fiber concentration withir. the mask for earn of tr.:three concentrations used ir. the test. While this calculation appears an approximation at best, it would again reveal the suitaoility of the Welsch and 3M masks for most applications. A sig nificant problem was revealed in that at the lower fiber :or.centratior.s (20 fibers/cc) the mask efficiency was markedly reduced leading in some cases to a greater filer concentration within "he mask in an atmosphere of 20 fibers/cc than i.. a concentration of Decsneer 3, 1971 Face 2 MEMO FOR FILE: VISIT TO McGILL UNIVERSITY 100 fibers/cc when the entire test .- n e d c; o was .-cr.sidered. This problem must undoubtedly be exam r.-v: in mere detail when NIOSH and C3HA present their proposals _n the near futur-' :cr imp rev -d respirator control. Th-_- report also attempted to arrive at an index of effective ness by combining the three factors of filter media e -M:iency, face leakage and ini.elation resistance. In this .-'ase nr. the Weis.;: .nits appeared to be the best, although the 1M J_ posables were s .\ifactory . From a cost standpoint tea- 'M ur.::.s will undoubtedly be most acceptable since they v/i11 pro: :cst from iO to I. per cent as much as the Welsch disposable ur....t . However, other factors will have to be considered, including the neater durability of the Welsch unit and the actual conditions cf use. For example, the 2M unit would be most satisfactory m a void, dry atmosphere while the Welsch unit with its inhalation and ex halation valves would be much more comfortable in any hot or humid atmosphere. It is suggested that any future tests on :a e leakage be conducted with sodium chloride aerosol rather than a .as. A byproduct of this test program was the observation th .t Dust Foe 77 respirators consistently failed to attain ev._n 90 p cent effi ciency compared to the 99+ per cent efficiency of the --.her satis factory masks. This is particularly disturbing since dust Foe 77 is one of the masks most recommended for use in J-M locations. This information became known to Bob Lchutz of the U. S. Bureau of Mines who contacted the writer severs. weeks age to verify what he had heard apparently from a meeting held in Canada. Subsequent to the meeting at McGill, Cliff Sheckler and I visited Mr. Schtz to give him, on a privileged and confidential basis, the information contained in the report. He was very much concerned about the results with MSA Dust Foe and asked if we had any unused filters from tnis lot that he could test in his standard procedure to determine whether a QC problem existed at Mine Safety Appliance. Sheckler will check with Bardswick and arrange for transfer of fil ters if they are available. Schtz thanked us for the information. He was also particularly impressed with the data concerning relatively high penetrations a: lew fiber concentrations and presumably also for short exposure periods at any concentration. Obviously in normal uss.ic, ribers will constitute only a part of the dust exposure so that one might expect a greater build-up of particulates on the mask than was obtained with exposures to pure fiber at 7 fibers/cc. Considerable data would h a v e to be obtained to investigate this problem in more detail. We uo not anticipate doing this in the McGill program. /. December 3, 1971 Page 3 MEMO FOR FILE: VISIT TO McGILL UNIVERSITY Bob Schtz informed us that the emergency 5 fib-.-r 'cc was being published in the FEDERAL REGI.VER on December 7 and chat he anticipated that an emergency 2 : limit michc be established in the not too distant futuic. A significant program is now underway at the Los Alamos Laboratory unaer the direction of Ed Hyatt to evaluate tecnr.iques ret quan titating the effectiveness of face fit by different r.is-.s using sodium chloride techniques. There is a good possibilit that this would end up with the requirement for "size-: "asks to meet requir -ments of different facial character .1st:_s. While no further program is contemplated at McGi :.. it spears highly desirable that we maintain good contact wita Bob Schtz and establish contact with Ed Hyatt at Los Alamos. As a side issue, the most recent meeting of the subcommittee if ANSI on respirator protection was recessed with no action per.di.vr: the recommendations which are anticipated from both NIOSH ano OSHA on the entire question of protection against exposure to asbestos. Probably these recommendations will be made in the usual .manner with little or no factual basis. S. SPEIL SS/rs cc : W. L. VanDerbeek, Denver E. M. Fenner, Denver C. Sheckler, ,)H J. R. M. Hutcheson, Asbestos R. B. Gresham, Jeffrey F. L. Pundsack J . P . Leineweber W. C . Streib