. Transactions - American Society of Heating, Refrigerating and Air-Conditioning Engineers. ourth hour 177,400 particles, etc., until the sixth houris reached when the count will remain practically constant. The resultsfor various materials have been plotted in Fig. 2. Note that the heavierdusts reach the maximum content condition early in the day while forwood or the lighter materials, the dust content continually increaseseven after the tenth hour is reached. This clearly indicates the necessity 88 Transactions of Am. Soc. of Engineers of exceptional care in the design and operat
. Transactions - American Society of Heating, Refrigerating and Air-Conditioning Engineers. ourth hour 177,400 particles, etc., until the sixth houris reached when the count will remain practically constant. The resultsfor various materials have been plotted in Fig. 2. Note that the heavierdusts reach the maximum content condition early in the day while forwood or the lighter materials, the dust content continually increaseseven after the tenth hour is reached. This clearly indicates the necessity 88 Transactions of Am. Soc. of Engineers of exceptional care in the design and operation of dust-preventing devicesinstalled in establishments operating 24 hours a day. CONSIDERATION OF THE RESULTS IN THE ROOM A dust count in itself gives no direct information concerning the condi-tions at the machine causing the dust. It is necessary to go further andconsider something of the size of the particles, the size of the room, andthe relative time the particles of dust remain in suspension. For instance,if a dust determination indicates that the average count in both a metal-. FIG. 3. 0 20 40 60 80 100 120 140 160 180 200Particles 6iven-cff at Source per Room Capacity,in Thousands CURVES SHOWING RELATION OF DUST COUNT IN ROOM TOQUANTITY GIVEN OFF AT SOURCE grinding room and a room where wood-carving machines are in operation,is 100,000 particles per cu. ft., it does not follow that the machines arecreating equal quantities of dust. This conclusion is frequently exhausting devices on one machine may be much more efficient thanthe devices on the other machines. Here, again, we are concerned with the density and size of the can compute by the use of equations (3) and (4), the amount of dustnecessarily given off at the machines to result in a stated quantity inthe room. Solving for A^ (the dust given off at the source), when vis less than h: N =-. n^ — Wi 4 ^h (5) When V is greater than h: h Theory of Dust Action, O. W. Armspach 89 Suppose
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