Per cent. 



No. cases. 

 Chemical extinguish- 



Per cent. 



24., 8 



ers 29 



25.6 



38.1 



Water tanks 13 



11. .5 



DUST EXPLOSIONS IN GEAIN SEPAEATOES. 9 



era! hundred acres of grain were destroyed. The grain loss in the 

 fires investigated reached about $50,000. 



MACHINES WITH FIRE-FIGHTING EQUIPMENT. 



A large number of the machines in which fires occurred were 

 provided with some fire-fighting equipment, as is shown in the fol- 

 lowing summary : 



No. cases. 

 No fire-fighting equip- 

 ment 28 



Water, steam, etc 43 



From this summarj^ it will be seen that less than 25 per cent of the 

 machines were not equipped with fire-fighting apparatus. Since 

 the percentage of machines that suffered a total loss (27.4 per cent) 

 is in about the same proportion, it is reasonable to conclude that the 

 fire-fighting equipment was efi^ective, especially so since in the ma- 

 jority of cases where the machines were totally destroyed no pre- 

 ventive means had been installed to check the progress of the fire and 

 explosion. 



STATIC ELECTRICITY AS A CAUSE OF EXPLOSIONS. 



THRESHING-MACHINE EXPLOSIONS. 



It was evident from the beginning of the investigation that a 

 large quantity of static electricity was generated during the opera- 

 tion of the separator. Workmen admitted that on certain days static 

 electricity was noticeably present around the machines. 



One case in which the owner thought the presence of static elec- 

 tricity was responsible occurred in Latah County, Idaho. This 

 machine was new, having been operated but part of a day. It was 

 completely destroyed as a result of the explosion. As the outfit was 

 located 15 miles from a railroad and 4 miles from the county road 

 there was no reason to suspect incendiarism. The crew was com- 

 posed of neighbors, or men known to be reliable. There was 19 

 per cent smut (estimated by counting the smutted heads) in the 

 crop. The weather was very hot and dry. After summarizing the 

 evidence, the investigator concluded that it was clearly a case of 

 smut explosion by electrostatic ignition. 



A similar case occurred in Whitman County, Wash. The owner 

 had experienced two fires, one in the evening and the other the 

 following morning, neither of them causing much damage to the 

 separator but destroying the surrounding grain in the field and the 

 threshed grain in sacks. At the time of the occurrence the machine 

 was threshing wheat with 31 per cent smut and was located 21 

 miles from the railroad and several miles from the county road. 

 43454°— Bull. 379—16 2 



