BUREAU OF CHEMISTHY. 269 



to life and property. In 13 recent dust explosions in the United 

 States and Canada.* 15-i lives have been lost, over 200 people have 

 been injured, and grain and property, valued at more than $16,250,000, 

 have been destroyed. These explosions have occurred in practically 

 every type of plant or manufacturing establishment where explosive 

 dustis created during operating processes. In addition to the explo- 

 sions in industrial plants, extensive losses have been experienced in 

 grain-thrashing machines and from fires in cotton gins and cotton- 

 oil mills. 



The expansion to a larger operating scale, tlie capacity for in- 

 creased production, and the development of industry, combined with 

 the introduction of new methods and types of mechanical equipment 

 for grain handling, have resulted in additional dust-explosion hazard. 



It is necessary to determine fully the nature and behavior of 

 these dust explosions, the sources of ignition, and circumstances under 

 which they occur, together with methods of prevention, before 

 effective control can be brought about. The bureau has been called 

 upon to assist in determining the causes of a large number of ex- 

 plosions that have occurred in various types of industries, in addition 

 to those occurring in grain-handling plants, and has definitely estab- 

 lished the fact that all industries in which these dusts are produced 

 during operating processes are subject to this hazard. The largest 

 losses at the present time are occurring in the grain elevators in the 

 terminal markets in connection with the handling, elevating, and 

 storing of grain. The lack of knowledge on the subject and the 

 absence of definite control methods have resulted in extensive losses 

 to life, grain, and property. 



The investigations of the Bureau of Chemistry relating to plant 

 dust explosions and fires have been very definitely conducted along 

 three distinct lines: (1) Dust explosions that occur during the 

 handling and milling of grain in elevators and industrial plants; 

 (2) fires and explosions in grain thrashing machines; and (8) fires 

 in cotton gins and cotton-oil mills. Very definite results have been 

 obtained in the investigations of explosions and fires in grain-thrash- 

 ing machines and effective control methods have been developed by 

 the bureau. In the Pacific Northwest, including the agricultural 

 sections of eastern Washington, northern Idaho, and northeastern 

 Oregon, these explosions have been controlled by (1) the installation 

 of specially designed dust-collecting fans for the removal of the ex- 

 plosive smut dust and (2) the application of grounding systems 

 for the purpose of conducting static electricity away from the ma- 

 chine. One of the principal causes of these thrasher explosions ap- 

 pears to be the ignition of the dust and air mixture by static elec- 

 tric sparks produced during thrashing operations. The bureau has 

 cooperated with the State fire commissioner of Washington and other 

 State officials in special investigations to determine the efficiency of 

 these preventive methods, and the results obtained have been suf- 

 ficiently encouraging to terminate the investigational work on this 

 phase of the subject. This part of the bureau's work has been a 

 definite contribution to the prevention of these explosions in thrash- 

 ing machines, and arrangements have been made with the extension 

 forces of the department for the application of these preventive 

 measures. The fans that have been designed have not only proved 

 effective in explosion control but have also indicated their value in 



