Document K6QyM6EdRvVvKyJd7q1b8wZYX

i i.'*- 'i*! DEVELOPMENTS? IN DUST SAMPLING AND COUNTING reformation throuF TECHNIQUES IN THEASBESTOS JNDUSTRY^^l^Mur* embracing. Turner Brothert Aebestoe Co. Ltd., Rochdale, England, and Asbeetotie Research Council roducixon Asbestoe dust has long been recognized as an industrial hazard in Grui micron* in length t Britain and an extensive survey of the textile side of the industry resulted .the.timely developer: ia tbe formulation in 1931 of. the Aabeatoe Industry Regulationa^TJvj#iV 'S'.S.^ji^*^i^.,reg\latlona;attenaj>ted to lay down standards to be achieved^and place!' Great. BrlUltuTl 'ffodergrouhd, 'was'V S ?' ^ npon the industry the onus of instituting measures to limit the dust haunt, "tiled its deposii, i ^.'thermal' preciplUtb! which had the effect of initiating a program of dust control that has con intake aide, designs tinued to the present day. To assess the effect of the measures taken, it wu ' the collecting slide, necessary to employ some means for the sampling and analysis of alrbonx '-validity of this elu' dusts and a review was therefore mode of the techniques available at tbe ' factor becomes imp time. The choice waa somewhat limited and the situation was complicated ment should be uset: by the fact that the equipment then in use had been devised for particuUt* dust clouds, whereas asbestos dust is fibrous and therefore does not obey h From the beg-inn' lilted to the sampl. the normal laws of settlement. fibers up to 800 mi* : While it must be accepted that the whole of the respirable frsction ef area of tome one-ha-, an asbestos dust cloud is potentially dangerous, opinions have varied over the old Thermal P i the years concerning what fraction of the dust cloud carries the major Instrument was oid.\, pathological hazard. Opinions have also varied on whether the physical or required a long tlm chemical properties of the dust were more important, it was therefore reasonable for couni. desirable to develop a dust sampling system that would collect the whole It wu at this *ts > or as much at possible, of the respirable fraction. |*to the United King* .* Earlier Work f. ordinate work on In the company with which the author is concerned, early dust sampllni fc aabeatoate. Their rru instruments.tried included the Konimeter and the Owens Jet Sampler, f;-. tod reliable method Both these Instruments take a "snap" sample and can lead to quit* *r- 1' edmparlsons to be roneous results in situations of varying concentration. They were therefon and In different ftc'j : ; I. .; soon abandoned in favour of the Thermal Precipitator,5 an instrument the dust spectrum capable of sampling a larger volume of air at a slower rate. It waa the but y fibers or fiber bubdl> ~ all-round instrument available at the time, claiming 100 per cent efficiency mum of 100 micros ; for particles under 10 microns in size, although it was subsequently found { arbitrarily taken as j to be much leu efficient above this point. The dust deposit was collected. n l diameter. This decia..glass cover slips, which could be incinerated before eounting'tu removr p~the^particle size dif ; any organic matter, and counting could be carried out microscopically it l ': reasonably conatant ; high magnification (800 to 1000 x . The Thcrmnl Precipitator waa the ' work has suggested' atandnrd sampling instrument (or muny years and provided invaluable s' carried out using * i ,oea . . -----. ..------ ---------, ______________ ftffOO 1601 %030 SCF-FA-5600 PRODUCED BY PORn