DUST CONTROL IN GRAIN ELEVATORS 31 
the formation of explosive dust clouds at the point of cleaning and 
the scattering of fine dust to other parts of the plant. On the other 
hand, the cost, both initial and operating, of a vacuum-cleaning 
system is high. 
The following points should be considered in the adoption of 
vacuum cleaning for grain elevators: Reduction in fire and dust- 
exploaon risk; reduction in insurance; original cost of the system, 
including installation charges; cost of operation, including deprecia- 
tion charges, power, replacements, repairs, and upkeep; cost of 
transporting collected dust to place of disposal; wages of workmen 
necessary to keep the house clean; house loss or difference in weights 
on in and out shipments directly attributable to the cleaning system; 
health condition of the employees; sanitary condition of the plant; 
effect on efficiency of the employees. 
The relative value of these points will vary with the size of the 
system and the market for the grain dust collected and whether the 
cleaning is done by a special Force of sweepers or by the regular 
elevator employees. The advantages of vacuum cleaning will 
probably give it preference over other systems under consideration, 
especially where the value of the plant in which it is installed is so 
great that the protection from fire and explosion afforded by the 
vacuum-cleaning system justifies the original installation cost. 
Improvements in equipment and reductions in manufacturing costs 
will soon make it profitable to install vacuum cleaning in most plants, 
in many of which the expenditure might not now be justified. 
NATURAL VENTILATION 
DOORS 
Large doors are often desirable, especially on the work floors and 
track sheds of grain elevators where dust is stirred up during the 
unloading, loading, cleaning, or conditioning of grain. Rolling cur- 
tain doors have been recommended for such places. Wherever 
possible doors should be arranged on opposite sides of the building 
in such a way that the greatest possible quantity of air will pass 
through the building. Such an arrangement not only ventilates the 
plant but keeps a large section of the floor clean, because of the 
wind which blows through the building. 
WINDOWS 
The workhouses in modern plants have many large windows. 
Windows on opposite sides of the building permit the wind to pass 
through, thus removing dust from girders, ledges, machines, or 
overhead structures. Ventilating sash or butterfly windows make 
ventilation possible during rainy weather. 
In some Canadian elevators a number of sashes are connected to 
a common shaft and opened or closed in unison. A slight pressure 
upon the sash from within opens any sash up to its maximum of 90°, 
which permits an employee to obtain additional ventilation at any 
point. An explosion in an elevator equipped with this device 
proved that the increased pressure within the building is quickly 
released by the forcing open of the windows. Once opened, how- 
ever, the windows can be closed only by operating the control shaft. 
