APPENDIX. 



RECOMMENDATIONS FOR FUTURE INVESTIGATIONS. 



In closing, the authors desire to offer the following recommenda- 

 tions for future investigations : 



I. Laboratory experiments to determine the limits of inflamma- 

 blHty as affected by the following factors : 



1. Density of the dust cloud. 



2. Kaeness of tlie dust particles. 



3. Chemical composition of the dust. 



4. Moisture content. 



5. Inert gases. 



6. Atmospheric humidity. 



7. Minimum temperature and amount of heat required for ignition. 



8. Sparks from metallic substances. 



9. Static electricity (not merely the voltage, but current measurements as 



well.) 



II. Field experiments on various types of machmes handling dusty 

 materials : 



1. Tests to prove that dust mixtures outside the limits of inflammability, as 



aheady determined, with reference to moistm'e content, inert gases, or 

 atmospheric humidity, can not be ignited under the most severe condi- 

 tions of ignition, such as those produced by an electric arc. 



2. Tests of various devices designed to prevent the propagation of explosions. 



RESUME OF SOME PAST EXPLOSIONS. 



The first large grain-dust explosion occurred in 1878 in the Wash- 

 burn mill, at Minneapohs, Minn. At that time the ''new process" 

 system of miUing, in which the grinding of wheat was done by mill- 

 stones, was in vogue. It was assumed that, owing to a choking up 

 of the feed spouts leading to the millstones above, one or more of 

 the millstones became empty, and the running of the two stones 

 against each other caused sparks, which ignited the dust in the 

 conveyor boxes and dust rooms, causing an explosion m the dust 

 room which destroyed the walls of the building. It is possible, and 

 even probable, that the fire originated from open lights which were 

 used at that time. 



Another very serious mill explosion occurred on June 24, 1913, 

 when a feed-grinding plant in Buffalo, N. Y., was completely wrecked 

 by an explosion, presumably of dust. None of the survivoi^s of this 

 explosion was able to give any information as to the cause of the 

 initial fire, but it is stated that without a doubt the explosion was 

 caused by the ignition of feed dust. 



