Document g2VyLkerYJZBkoo5bG61JoE5q

FILE NAME: Brand Insulations (BIN) DATE: 1969 May 6 DOC#: BIN003 DOCUMENT DESCRIPTION: Unpublished Draft Repot with Cover Letter -- " bcc: W. P. Raines -GHy.<w/enc) t : t ; . * > a y 6, 1969 File 259 v ` > - Dr. Irving j. Salikoff Environmental Sciences Laboratory Mount Sinai Hospital School of Medicine .100th Street and 5th Avenue I' New York, N. X. 10029 . "* t M: Dear Irving: li.v hr-. Enclosed is my. portion of,our paper on "Fibrous Dust Respirator Protection". As soon as you have an opportunity to.read it, please call me. The figures in the paper <Figure 1, Electron Micrograph of "standard" Fibrous Dust, and Figure 2, General View of the Face Mask) .will'be ready in a day or two. I will send them as soon as they are avail able. , * * > Sincerely yours, - i : ' .{V J .. i. *tly ./' Enc. if:, , r. *.--> t.; ' A - V ; > ^ s. . ***r ' A * I * V * * Design criteria *.. ; ' . . . The following specific criteria were established for tha ' . design of a face mask which would gain a high degree of .- acceptance o r the part of; workerss.'., ; : ' , " 1. The mask had to bs.effective against both particulate , and .fibrous dusts*,'and it`had .to.meet the Bureau of Mines 'J* . ' . : , n * ' *' * -. .' * " . \* requirements for approval, under Schedule 21BU6} ' .. < ! * * \.u ' 2. The mask was to ba designed `to. bo used for. one day and ` " \ -V .; - .. then it was to be discarded."-..'There are a number of .' v> <'A/' . i-. masks on the market today.which utilize a disposable-.,; filter element which fits-.into, a more or less .permanent . . face-piece that is used over .and over. Although some. of these masks are1relatively effective, unfortunately * . v `the most effective ones!have--gained only modest accept-. \%: \ * /*.* * . * * ''*' -* e ance on construction site.jobs*! There are several . * - t-W"* . ..'/.* * * -- , v ** .. 'reasons for this low rate of usage. .Unless a job-site.' v- .'' facility .is provided; ,to:repair,;,replace, and maintain the ..^face-pieces, they .quickly 'become ,,dirty and very unappealing ' "*- *, . ' .> jr *** . ' ; "'from the wearer's point^of,-View.*. In general job-sitev '-' repair and &&inten&ce .facilitie* for f&e* masks are not SbiiA toAi li uiilgli oh oieHVa ra.flk loll r 'i - . * f- V *' economical thut jtp IjoJ U `St# r 3. 'i'h mask had to have a low pressure drop across the '* filter element to minimize breathing resistance dur~ * . . . .. `lng day-long use, < ' . 4, ",The worker had to fo,tabla to talk;through the mask ' - and be understood at\a distance of- at least 3, feet. -..\ %o he mask had to be comfortable to wear# and it had to a *\.* 'i -r fit mar than 90 per'sent of the various facial types- . ' "* V i ' ' that would bs encountered.,- ` , - !. f. . ,, , > ,t \ *' ,i'.- * -, * * % ... ',' ; ` \ y Development of "standard" fibrous dust ... , In developing a filtermedium ..thatwould be effective against fibrous dusts, it was'necessary first !to develop a "standard" fibrous dust.. In general, -tha;available standard testa for the , ' ' "r ', 'efficiency of face mask, filters against dusts utilize a .. standard particulate silica ust .or an" aerosol' dispersion of spherical liquid droplets.'".For the most part it has been * v 1 , ;' . . .. * ; assumed *t*hat filter',' me,diia,`wLhi*'ch! ar'*e *e,ffec-t'iv,*e against ' -particulate dusts are also effective against fibrous dusts. 's important'in.this fsfeudy4fee.`meagusfe directly..tthe effective . . .- W V>r V i v ? `* * . VIv. ness of various filter, media against a fibrous dust such as Si.;' v\si /* J.v! V`, M l .'9 : /; t . W . z i " >> ' .- - It.was found that & satisfactory ."standard" fibrous dust could s . V% *`**1* * *' ` a.:* i ^ *. be prepared by micropulverizing and air^jet-milling a . specially cleaned source-of chrysotile asbestos fiber (17) v 1 7 *. v ' : ,X,:- -.Xtu`.i-r: ; - .; '-'.VJ?', '* ' " , 7 - , ' Tha fibrous dust prepared in.this way was predominantly of respirable size with most of the-fibers less than 10 microns long'and lass ,than .1 micron in diameter (Figure 1). This - * ' ' .* , ** } r n r ' " ` duat could be dispersed in'a satisfactory manner .with the . * .i< 1; .*'H ' - ' ' silica dust apparatus and feed mechanism described in Bureau - * * t*- 4+& . *. of Mines. Standard Method,NO. R-6 (18j ^ * \ ' V , Essentially this apparatus and method consist of aspirating < * * - , the. d u s t into an airafcream, and then;paeslng the dust through a cyclone to drop out the. larger particles before < the dust-laden air is passed into a large chamber (8 ft by 8 ft by 6 ft) in which the face mask and filter are cemented . over'a port. Air is drawn through'the mask at the rate of 32 liters/ralnute. In the case of fibrous dusts, the-air which has passed through ,the mask is siltered through an MSA 41106B glass fiber filter backed up with a Millipore filter. These filters were weighed before and after the test to determine the amount of .breakthrough in the mask under teat.. Xn several cases the filters .were examined with an 4 4 y . , . , *. . * * electron microscope to.detect any asbestospresent in quantities too small to be detected with the weighing procedure, . * ' . . < . * . Tests of mask filter media against asbestos dust . . , A number of commercially available .roaiks were tested against the "standard" fibrous dust along with the JMS prototype mask' developed as part of this project, 'The result of these tests, i* , ii , 1 .* * , k * i * . is shown in Table 11, All themaaks, except one, were rela- . tively efficient in reraov,,,.g chrysotile asbestos from the air.,-'"  10- Sven though a number of the masks, tested ware less than ' 9 9 per cent efficient against stan(d* a* rd silica dust, with Kmm the one exception noted, .they were,-all more than 99 per `. s-*.; . . . cent.effective against ,chry3otile<asbestos duat. The',.. *' t 7 1 . -; '/ %***?*y' *- filter media used in the masks .posted'ranged from rosin - . , . , ... .*..** f r j * - i ' 1 .*. i.* 'i* t,.** ,. * i . .*. * . . .. wool.through mixtures .of fine glass-fibers with cellulose \ * ... ...... v-. or synthetic fibers to open-cell" urethane foam. The '.latter was least effective against'rthe asbestos-dust. . r ...-j. ** . - .Based on these resultsY it .`appears., that finely dispersed ' ` chrysotile asbestos may toe more, easily filtered out of ', . ' . . .... --`'A - ' an airatream than very finely.divided particulate dusts -'V :- -v*-' } l r k'if, i \ . such as silica, it must be .pointed!'out,;howeverthat 1 ______ * ^L-- ..... --T ----- ,-- ,, ,these results apply only to chrysotile ashestoa.; ..Amosita < - *. . 1* * ' `'. * * * * *' " '.?'"i, .and crocidolite asbestos 'have not'fbaen tested in ;.this way. -tv T-... . and since these fibers tend .to break down into relatively " . " -- - r * - - v - f r: ` - f ;. rigid, syioule-like fibers;-.they may show.'a different fil tration behaviorthanvdoesthe relatively flexible ` -------- _J-- 7 y-- ' ' < i-- r~* - : , chrysotile fiber.' :.; \.k i. ' <w ` * t*.,, 4 ?/V^ f V-' face mask design',;' V.-l' TM ----- T v S* - * ' ; The moat difficult part of. face.respirator.design is the. . _ -# v -' - .T - . * f^ce frame Itself*. r.If -title .iftca* frame does not provide a * \;i; .tight, non-leaking seal, against the face, it really does. '* J - i. , . . . * . , 'is ' '.M, * I V -5V"w^ i>; The OMS prototype mask utilizes a rubber compound face-piece with an aluminum wire insert., The purpose of the wire insert is to permit shaping of the fsee-pieee to the contours of ' ' *. . t r ' 1 , i" ' - the individual wearer's face. iThe^overaXl appearance of the 4 ` * .......................... ..... | mask is illustrated`.la figure 2, The wire insert is dis- continuous ao that the face-piece has, in effect, a hinge . . * i*.. .. ; '*' a oaoh side of the wearer* mouth." The hinge facilitates r # V *. * . ' **' . \ % . v' 'the fitting of the sk. to;the individual, and it alao accomiao- .. * i -?*** **?*m*' dates movement of the mouth when the wearer speaks. In some of the early prototype .masks,'a bead of apodal 'ailicpna gum was an integral part of the face-piece. The `'`-purpose of this gum was -to form*,4a semi-liquid seal between .. . `i . :t'4- , V rthe face-piece and the wearer's face; However, tests of \* 1 ' - - * . . ` J.v **j'*. the efficiency of*the prototype, mask'assemblies did not show any particular advantage from the use of the silicone gum, and it was not used'in the.field trials of the mask. Field testa of the JMS mask~ ' via' . \ *** * *1^' * " >- .:<A. series of 5-day field- trials :p the mask was >conducted * ` i' . . . l,f`*'/* :Y .^'"V ' .with, the cooperation.o the*International Heat and Frost .>. insulators and Aabaafcda -^orkfra^ion artf ({is, M evaluated: 4diVtinpfeorvv fittea types of masks were * `"VA,*.,*.fTtySvit-,+.j**V. s' <. `y 1A: -*.v- *. !s.j i.-i`f| ,, .,v*. *r` ' u Typ. A - JHS prototype'.n.fe|.vt!5*&!`"*i ,Six groups oi! six men were selected to test the masks. The workers in each group wore each.mask, but in a different :* sequence. This was done to remove any tima or,sequence dependence from the test.' Each worker wore a given mask ,for half a day (approximately ,iy% hours) and then he com-. - pleted the type of questionnaire' shown in .Table 12* It is * * *. * , ' e* ' i __ .interesting to note that prior toYthe tests many of; the ` /'V /'***** men on this construction site had been U3lng a^nu1aance-typ'o `dust mask which, although it was not'particularly effective ' -.against respirable-particles and fibers, was comfortable. / . ' ! * .. ,r * * * t . * * k In rating the masks,-'the workers .showed a definite preference for Type A as the best mask.- This preference appeared to -, H ... be associated with the use of an exhalation valve in the -y^ ^ ; .! ' .- r , .-mask.. Type B and Type C masks.were preferred .the least by approximately equal, numbers of.workers*;-This lack-of ' ` '. *; . " * - , preference for or against B relative to C ('indicates .that ' 1 . * * : ..v v . . 1 * '* breathing resistance was.not avserious factor in these masks. '/'**1 '' .*V.''*&.*/* ' f- - X 4 * . . * - jt i 'i.. v - , * a - u- f * Two major objections .were raised, to. all the masks regardless . - - . :*O v \ J - **" `Of type* First, thevcorafort;of fit, particularly.around-the . . . ** y -. bridge of the nose, was a-problem .YVSecond, the bulkiness of- - - * - - V.Jyfffiirf'. ' _ '' .. , the mask interfered .with downward*-vision,, and ,it<interfered . '.with glasses when these wers.vorn by the worker.. These ' v - Y * v s-'. ' ' : ' - objections are serious.enough,'we.believe, to require some <: ,y. - - - . . . . . vr redesign of the face-piece-and the:shape of the'filter .'element ` ' if... . f'.., -.before the mask will .meet--the..-`design criteria established, ;Y` .. r . ... ' .- ..j, .. for it. However, we are convinced Athat it is:.possible to Y ,. - -: - ,' /V. *' - c xi -/if . . . i , * t* * , /.* 4 .. * . . i . . -* i v y ,Vv`->- .Af?'V -. .- f ,,-' ' " .. >I'st-:v.;*" Ili-P .*a iv si If V .i ' *. -'V u -*- 1n b . 5 * * : *. . *. <>' . *.. . *' * M * ,-v . . t . j-,t ' ' ,*y..Mt4l>' ?7` *' 14 i 'J ' develop an acceptable face, respirato.-mask which is highly .;', ' /'* V ' " .'l' '7-A&L' ` . '/. , affective against fibrous dusts'.,fStibh- a ask probably -can; . ... ` B [1 '.'i j - .u . * a*: . * . ... 'V* i * * *. It. '*,s;v Acknowledgement . -j;, ` . *a.*`m.V'*'/*`Vsir.** **-V*. `* *r*- t 1*#*' . tw w. ; *' h I ` We,wish to acknowledge the; uaeful:;d8CU88ons vith.Mr.-. Earle ; ' .' ' ' .. - - -;V"- . * . ", .. t S.-f." .:'t . .; Shoub and.Mr. R./H.v SchUta f-it^f^]i>ilftueau'of,Hines,'V*;,v': .u*i i..` **? ahv UAeTl!' . M A A A A M W i M w ''' ' >... :. .V - - 14 , 1 j ,m : A ' REFERENCES. ... , J /}.i'X.*- *.-V4. '` ' 1-15i Dc. s.alikofif'a portion^o ;.fehis paper. ; `: . i. V, r\; : `y- ' . Respirators Against^iPibrous'. Dus^.j' to be published. ; .VW.\ ; ; ' V -if- ; > *... ;*. - ? 4' ' '-.18;. Brenenborg# F .J. ' "testing`.'.espiratora Against silica , . .DUSt * * .r . * *,,. t . * - _ * * VK. `-i fif 4> .-y ;$* j .. . ..-.-v .;.V 4 v > V v ,7\v .. . . - . - > . ` - V/ 'I V ... *>* r . - ?