30 BULLETIN 1373, U. S. DEPARTMENT OF AGRICULTURE . 
out heating. This part of a vacuum-cleaning system should be 
arranged in units wherever possible, so that one piece of equipment 
can be cut out for repairs without impairing the efficiency of the 
entire system. 
ADVANTAGES AND DISADVANTAGES OF DUST-REMOVAL SYSTEMS 
The advantages and disadvantages of the cleaning systems here 
described should be carefully considered before the equipment is 
installed. Sometimes the cleaning requirements may not justify the 
expenditure of a large sum of money for an expensive cleaning sys- 
tem; the saving in labor and insurance charges would not be sufficient 
to provide a fair return on the original investment . To be economical, 
the installation must reduce the number of men employed to keep 
the plant clean and also cut down the dust-explosion hazard enough 
to reduce insurance rates. 
In small plants, which are cleaned only periodically by laborers 
or the regular employees during their spare time, brushes and brooms 
are generally used. 
The advantages of the broom method — low initial cost of equip- 
ment, low cost of upkeep, low operating cost, and general adapt- 
ability to various conditions — are generally outweighed by its chief 
disadvantage — that the fire and dust-explosion hazard is greatly 
increased during sweeping. Moreover, it is difficult to remove the 
dust from corners, cracks, or crevices with brooms; the collected 
material may be scattered by drafts over the section already cleaned. 
The dust thrown into suspension later settles, necessitating a second 
cleaning. Some method must also be provided for removing the 
dust from the building after it is swept up. 
The greatest advantage of the floor-sweep system over the brush- 
and-broom method is the facility with which the sweepings are re- 
moved from the building and -the fact that no additional labor is 
required for this work. Less sweeping is required because the inlets 
of the system are at points where the dust generally accumulates, 
making it unnecessary to push or sweep large quantities of dust for 
any great distance. The disadvantages of the floor-sweep system 
are practically the same as those of the broom method. Brooms or 
brushes must be used to sweep the dust to the inlet of the system. 
The light dust thus stirred up creates an explosion hazard and dust 
can not be easily removed from cracks, crevices, and corners. This 
system is the one generally used. 
Although vacuum-cleaning systems have not been entirely satis- 
factory in the few grain elevators and feed plants where they have 
been installed, it is generally admitted that their failure has usually 
been due to defects in design and installation. The indications are 
that the newer installations in grain elevators will be satisfactory. 
The vacuum system is undoubtedly a safe method of cleaning, and 
it is far more efficient than any other method. The suction lifts the 
dust out of cracks and pits that brushes pass over, thus making a 
surface much cleaner than is possible with a brush or broom. The 
greatest advantage of pneumatic cleaning, however, is the elimination 
of the hazard of suspended dust. Instead of stirring up the lighter 
material, it draws the accumulation into the system, thus preventing 
