CHAPTER XII 
CONSTRUCTION OF VENTILATORS AND FLOORS 
UN LB 
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NE of the Canadian houses has a unique venti- 
lator. Just before the gas is generated the 
hinged trap is pulled up tightly against 
the felt, and the rope fastened to a cleat on 
tne side of the house, as shown in Fig. 66. Before the 
FIG. 66—METHOD OF VENTILATING A FUMIGATING HOUSE 
(AFTER LOCHHEAD) 
door is opened the rope is loosened, and the weight 
brings down the trap and allows the gas to escape. A 
ventilator of this kind having the trap opening into 
the inside is prote¢ted from the weather, and is not 
subject to the troublesome warping of exposed cap 
ventilators. 
An Ohio arrangement.—In his practical work in 
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