Document 6bEVLjZ3Lj4njo1k08vKvdke4

"J 1 -?ra.> - er ^<i-u:'ic:urerc ' Assoc u abcrshav-Cccter Associites Preliminary `.sport ca Analysis of Air Samples Collected in a Fuiliir.g vith Sprayed Mineral Fiber Fireproofing Lining the Return Air Soace. luring the ^period July 7. to July 9, 1970 , ai r samples vers collected at tv; points^Vitn'in t h e"* &I r ' *d i s triVu^idr.^syITtaf*e.*l tree> an - jnessniiMKe Francisco office building. The purpose vas to male a preliminary assessment of the prosaoilitythat asbestos fibers vere being added to the air stream in its passage over sprayed mineral fiber f ir*trccfir.g . The fireproofing material had bees applied to structural steel members of the building during its construction in 1966. The portion of the air distribution system selected for this test supplies air to the 32nd to klst floors; the airnoving equipment is located on the **2nd floor, vhich is entirely given over to mechanical support equipment. Air is supplied to the occupied spaces cn these floors through enclosed sheet metal ducts partially lined vith fibrous glass. Air is returned through the spaces betveer. the structural and suspended ceilings on each fleer. It is conducted thence to a large return shaft leading to the -2nd fleer mechanical room. Approximately 75? of the returned air (depending on external temperature) is recirculated, the remainder is discharged to the outside. The returning air is in contact vith sprayed nineralfiber fireproofing curing most of its passage bach to the nechanical room. Samnllr.g and Analysis Air samples vere tahen at tvo points, both vithin the ^2nd floor nechanical room. The first point ("Supply") vas immediately dovr.s t re an of the filter through vhich the ccmbined recirculated and outside air pass before delivery to the occupied space of the building. The second point ("Return") vas the top opening of the return air shaft through vhich all returned air passes before its eventual recirculation or discharge. Four air samples vere ta/.e.t at each sampling point as matched pairs of samples; the sampling rentes vere coincident at both locations. The time periods vere: 15C: - IcCO or. July 7; 0900 - 1500 and 1500 - 2000 on July 3; and C?CC - 15CC on July 9. All air samples vere tahea by driving air threurh -7 mm diameter Millipore organic membrane filters ( 0.6. um near, acre sice) at a fiov rate of 0.S cubic feet per minute. The filter holders vere placed ir. the moving air streams at points vhere the linear air velocities matched the filter face velocities vith- C 0279 i 1 y v ii : the dust sampler collected cr. the i1 ; v - by tic method reccr.ncr.dcc by the United States Public ieulth ;arvl2a for :r.c determination o:' asbestos fibers. A portion of -c- r.er.srar.e filter vas placed cn a microscope c-l-ice, cleared by the atditicr. cf a drop cf a mounting medium matching the index cf refraction cf a;-* filter, and covered vith a cover slip. -he mounted filter vas then examined vith'phase contrast microscopy at a magnification cf U-cX; ICC ranaem microscopic fields (defined by a Pcrton eyepiece reticle) v-:e so examined, and ail fibers counted and placed in site categoric Che location of each fiber vas marked, and the slide vas transferred to the petrographic microscope, vhere (also at a magnification cf 12 0 X ) the fibers vere.identified. The identification in this case vas limited to deciding vhether or not the fiber in question vas asbestos -T-,The ^umbers ,o:\ asbestos .^fibers ^seen vercr.csnverted ;c concentrations , expressed in fibers peT"Jliter*'olf'"s'Sp'led^air /,* by'Vc**'' tahing into account the area counted, the flov rate, and the sampling time. A secondary analysis vas the determination of the gravimetric concentrations cf all particular matter. The filters vere veighed { 0.C05 mg) before and after exposure; the change in veight vas divided by the number of cubic net'ers of air vhieh had passed through the filters, and the results expressed as micregrams of particulates per cubic meter of air. All sample filters have been retained and are available for electron nicrcscope analysis, if this becomes desirable. ' Results In Table I are shovn the results of the air sampling program. The results are shovn both as asbestos fibers per liter (f/1) and as total particulate mass concentrations (ug/s'5). Asbestos Fibers and Total Particulate Concentration; ii me j 7-7-?C 1* 1 15CC -- ^ vc w c -J t C$00 - 1500 i . -- I-- < V 1 7-5-7= 1500 - 20C0 c$oo - 1500 Sup oiy f/1 8/=3 1.2 u 1 ?.et f/1 I '' ug/m i 1 '1 * i 1.2 5 5.9 i 2.7 6 X 6.9 ' 2-1 i , i ,i J 6.9 to ! ! 1 i 20 ii : ;i $6 1 '.1 * h c - these ccta ere far frcn ccr-pcctc, ;cr.:c.r::-e-r. cthe ;'i;cr concentrations ir. ;::s- su??I:ec sir and the aciectcs :i:er :or.cer.zra:ior.s in the air vhich has passed ever the strayed nineral fiber fireproofing shovs a clear trend. The increases, arc- larger than v have seer, in buildings in vhich the air cv:: r.st cor.c ir. contact vith this type of fireproofing. Further, the- increases statistically significant vith alpha = C.C25. (There is only a 1 trchasility that these results are due to chance.) There is thus no reason to believe that further air sampling in this building vould yield results narkcdly different than those given here. <*J U N Outside covered bui1di 6 sinala -ove sanples vere being taker, during the sane period of tine this report, at another caroling site near to this The "asbes t os'*"Tiber 'concentrations found -therewere - those found here in the "Supply" sanples and significertly the concentrations in the "?.eturn" sanples. Ve nust erphasine that this report is based on United sarplir.g on cne building syster, and that extrapolation to other buildings, or to air.distribution systens in vhich the air velocities nay be ruch different, is not warranted. -Nevertheless, our prelininary conclusion is that, in this building, asbestos fibers are being added to the air stress passing over sprayed nineral fiber fireproofing. Report Prepared By: Douglas ?. Pcvler, M.S.