Distribution of HCN Gas in Greenhouse Fumigation 9 



The fumigations were carried out in the same house, with the 

 same charge — i ounce of NaCN to i,ooo cubic feet. The result 

 as shown by the graphs are very different. In figure lO the 

 greatest concentration is foimd in the comb, within 2 minutes 

 after the charge was liberated. The decrease in concentration 

 is progressive except for the position over the middle bench, 



5 6 7 



MirsiUTE5 



Fig. 2. Graph of Fumigation No. 2 



A, outside bench; B, middle bench; E, center bench; D, out- 

 side collecting tube; E, middle collecting tube; F, center collect- 

 ing tube; G, comb collecting tube. 



which slowly increases until the end of the fumigation. No. Ii, 

 on the other hand, attains maximum concentration in the posi- 

 tion over the right greenhouse bench, with only a moderate con- 

 centration in the comb, and then decreases rapidly until at the 

 end of the fumigation the concentration throughout the house is 

 approximately equal. 



Figures 6, 12 and 15 also show the general course of the 

 fumigation very well, and No. 12 ser\-es to illustrate again the 

 variation which may take place in distribution. In No. 12 and 15 

 the charge was the same and the house in which the fumigation 

 was done was the same, but in one case the comb had the high- 

 est concentration, and in the other the right-hand bench. Figure 

 6 shows strikingly the reason for failure in some cases to get 



