GRAIN-DUST EXPLOSIONS. 3 
Early in the investigation it became obvious that experimental work 
was necessary to determine the circumstances under which the ex- 
plosions and fires might originate and to establish definitely the possible 
causes. Because of the equipment available in connection with its 
milling course and its convenient location to Eastern mills, The 
Pennsylvania State College was selected as the best place for an 
experimental mill. This phase of the dust-explosion work was 
accordingly assigned to the experimental department of that insti- 
tution, the experiments being conducted under a cooperative agree- 
ment between the Department of Agriculture and The Pennsylvania 
State College. The materials were furnished by various milling 
companies at the request of the department. This bulletin gives a 
description of the equipment of the mill, the manner in which the 
experiments were carried on, and the results obtained, together with 
an outline of conditions conducive to explosions in grinding machines 
and the effect of various preventive devices. 
Aside from the relation of explosions and fires to grinding processes 
in the milling industry, the phase of the grain-dust explosion problem 
discussed in this bulletin, the department engineers have established 
a number of additional possible causes, among which may be men- 
tioned: The use of open flames, lanterns, gas jets, etc., defective elec- 
trical equipment, frictional electricity produced by friction of pulleys 
and belts, ehoke-ups and friction in elevator legs, inefficient methods 
of dust removal and collection, and the continuance of dust rooms. 
Recent investigations by the bureau have revealed the surprising 
fact that many of the owners and operators of large grain mills and 
elevators are unfamiliar with the circumstances surrounding grain- 
dust explosions, as a result of which dangerous conditions are per- 
mitted to exist. Recently. a fire, originating in a dust explosion at 
the top of the elevator leg in one of the large grain elevators in the 
East, destroyed almost 1,000,000 bushels of grain. The present cri- 
sis makes it imperative that all known precautionary methods be 
adopted. The Department of Agriculture is therefore redoubling 
its efforts, and has arranged to conduct a special emergency cam- 
paign throughout the United States, to the end that grain dealers 
and millers may become familiar with the work already done. The 
field engineers will assist the millers and operators of grain elevators 
in the installation of preventive devices already developed by the 
Bureau of Chemistry. 
THRASHING-MACHINE EXPLOSIONS. 
The second division of the department's investigations into the 
matter of grain-dust explosions comprises an extensive study of 
thrashing-machine explosions, which has been confined largely to 
