Document jz3on1O0q708y3058a9gwg3N

FILE NAME: Raybestos-Manhattan (RBM) DATE: 1954 May 19 DOC#: RBM098 DOCUMENT DESCRIPTION: Letter RE Dust Counting Equiptment & Investigation of Dust Counts with Bibliographic References X ft Hr* R. % '/ : flay 19, 1954 Duct Counting Equipment Mr* Cilloy hno roquofltod that on invcetigation bo rando of th dust coxmto throughout tho mill and poanibla mothodo of reducing tho amount of dust for improved hyganic conditions. Mill oonagomont in ever working on this problem and duat counts aro periodically made by tho Bureau of Industrial Hygien. Tho problem of dust counts and methods of reducing earn aro under active study by tho Air Uycioao Cormittoo of tho Asbaatoo Textile Institute. Tho first stop la any duot count program is to select suitable equipment. There appears to bo a difference of opinion relative to equipment as tho im pingor collector io generally uosd hero vhlla tha thermal precipitator is used in England for collecting tho duat particles. It io understood Mr. Luttenborgor io arranging a conforonco with Dr. Shiism of tho Pennsylvania Bureau of In dustrial fjygiran for a dircusnion of duat counting equipment* Also, duat counts will undoubtedly bo diccunood at tho Juno noeting of tho Air Hygiene Cecnaittoo of tho Asbestos Tactile Inotitato. For background Information, a brlraf litoraturo noarch was made in Chemical Abstracts on dust counta, in which tho following facts wore noted relativo to tho operation, limitations, and comparisons among various types of instruments. Many-typos of equipment for determining dust counts or dust concentre tiono have boon developed. Tho total amount of duot in air can bo determined by drawing a known amount of air through a suitable filter and the amount of duat determined by weighing (1). Stokingor and Luskin (2) report tha electro- static precipitator in which the duot particles are toad to sottlo out by an eloatric field io boot suited for tho datorniivitioa of duot concentrations. However, it io not suited for also-distributlon of most particulates because of isa segregation along tho collecting surface, and because of aggregation of particles* Several typos of apparatus are suitable for duat counts. In tho iapingor typo (3) tho air 1b drawn through a jot to impinge on mtor. The duot is retained as c bugpenaion from which it io alloxred to settle out on a special type of microscope slide and thn dust partioloa counted. It efficiency lnareaaea with the sampling velocity which ia normally about 23 liters per minute. Ita efficiency is about 40$. Charabury of Ponn State reports (4) tho nidgot iapingor method of collecting, analy sing, and omluatinff dunt ia purely amplficftl cud give a only relative' -1 ' Mr. H. L. Mooro - 2 a; ? t; < >3 roculta which are subject ta orroro inJLatorpratation if connidortitlona cro not given to llmitationo ooneornod with tho ability of tho apparatua to drav duat into tho no'/alo tube,. tho Loss o f t h o d u a t J^Jiha liquid, tho chattering of tho duat cn impingement, tho stability of tha duat in the liquid, the siso riingo of tho duat, to. Vhon tho aoooisaary corrootiona are applied, tbo midgotiaplngor method yields ronulto comparable with other methods of evaluating duat. In tho caacado lapactor (3), tho air io paceod consocrutivoly through four jeto of docrcdfliag oico onto a glass lido coated with an adhesive*. It i3 reported (2) to have given excellent partiolo~giao nnaiyeou in tho sice range of 0.2 to 50 microno* It yields rapid and roliablo results in tho charaatoriaation of dust and can bo used for tho sixo distribution onalyooo of mixtures of dusts. Bolav tho useful range of tho cascade inpactor (2), tha thermal precipitator io tho moot uooful inotrutuont. ' This instrument (5) oakoo uua of the faat that thoro la a duat free opaca around a hot body, in this case an electrically heated vira placed between microscope cover olidos on which tha duat is dopooitad Toots chow that tho Instrument collects aInoat 100$ of th duat partlelco in the six* A vory slow sampling rot, normally 7 cc/mia., is required. M.qglll in describing techniques for smog analysis (6) reports a cascade iapaotor was used to collect camples ovor brief periods of tin and to follow ataocphorlo changes cloooly. A thermal proclpitator is advantageous in that it ap pears to collect all fine particles, but it must bo operated at vary low air flow rates. Several photoelectric dsviooo and dust cameraa for aeecuring directly tho concen tration of duat partial in tho air have boon roportod* Those arc be sad on tho "Interference of a boan of light by dust partiala3 in tha air. For accurate dust counts, npacinl attention aust bo given to campling teahniquoo as, tho ooltiCtion of looation, tho uoo of mixing baffles, and tho nood of iooldnotio Banpling (7). Since ltjuas boon reported that thoro is no unfavorable physical reaction froa aebostoo duat" in thoJLunga which in under 10 raicroa or ovor $Q~microns in" *~ long^',~bur_ oa^aclo should bo directed toward counts in that oiza range. This appear to ba tha mage-in which the caoando impaotor or impingor Io moot offeoti'. while tho thermal proelpitator io moot offectlvo for finer particle. Thansforo, tho cascade Inpactor la given firot choice and tho inpinger nocand choioo* Tho accuracy of any duat counts will dppend noro on tho car of taking the sample nd making tho counts than on tho typo of apparatus uasd. no co Mosers. Cilley buttonbargar S to fl M. S. Kaior RSFKKE?1CS3 (1) Duat In Industrial Atmo aphonia* Dotormination of naaa concentration by tha Volatile Filter Matbod, P. F* Holt., Motallurgin !!, 52-A, 1951* (2) Air Pollution and particlo-sia toxicity problems. H* E. Stokingor and 3 Lankin, Uucloonios, 6, Ho* 3, 15-31 1950 (3) Duat in Industrial Atmospheres. Tho impingor and cascads tnpactor. P. F. Holt, Katallurgia, 13, 250-9, 1951 (A) Tho uan and limitations of tho midgot impingar for counting dust. H. Q. Charabury, Proo. Rational Air Pollution Symposium, 1919, pg. 181-92* (5) Dust in Industrial Atmoophoros* Determination of tho particia count. P. F. Holt, Motnllurgla, A3, 151-2, 1951. (6) Techniques ployed in tho analysis of Loo Angoloo Smog, P. L. Hagill, Proo. Rational Air Pollution Symposium, 1919 pg. 61-3. (7) Sampling of duot-ladon C. J. Staimand, Trano* Inst. Chemical Engineers, 29, 1951, pg. 15-11. Partinoat Artlolaa An appraisal of prosont-day fiold inotrumenta. A. 3. Sattorlind, An. Ind. Hygiene Assoc. Quarterly 9, 35015, 1918 Relation betveen and precision of dust counts. C. E. Brovn and U. H. Schrcak, U. 3. Bureau of Hiaoa Report, Investigation No. 1568, 1919 (35 pp). i ; v