282 WARMING AND VENTILATION. 



or gas-burners which they contain, which often produce a degree of 

 heat in excess of that necessary to warm the room. 



The general rule, which requires that the foul air should be drawn off 

 near the floor, cannot be exclusively followed without causing currents 

 of air heated from 85° to 95° to fall upon the students. It is, then, 

 necessary to carry away the hot gases, the products of combustion, 

 through the ceiliug. But at the same time it is necessary to admit the 

 fresh air, which in that case must be cool, at a certain height as far as 

 possible from the floor. 



But if the same room should also be occupied during the day as a 

 study or drawing-room, and if it were then ventilated according to the 

 usual rule hy drawing the foul air off near the floor, it would be well at 

 night to maintain that ventilation in order to assist the circulation and 

 the descent toward the floor of a part of the fresh air brought in, of 

 which to make up for the heating-effect of the lights, there should be 

 a much greater amount than during the day. 



Observations made in a school of design in Paris attended every 

 evening by 200 to 240 scholars, and lighted by 90 gas-jets, consuming 

 together 320 to 350 cubic feet of gas an hour, led for this special case to 

 the following rules : 



1. During the day, regulate the amount of foul air drawn off at the 

 floor-level to about 530 cubic feet for each adult scholar and admit the 

 fresh air near the ceiling. 



2. For night-sessions, make escape-openings in the ceiling, the clear 

 area of which should be calculated at about 88 square inches for every 

 1,000 cubic feet capacity of the room. 



If there is no loft above the room in which the ventihiting-pipes can 

 be carried, special pipes may be placed at convenient points, removed 

 as far as possible from those at which the fresh air is introduced. These 

 pipes should be supplied with convenient valves, in order that they 

 may be closed during the day, and the amount of the hot gases removed 

 at night regulated. 



3. Place in the two opposite walls of the room, or at least in one of 

 them, at the height of 10, 13 feet, or higher, if possible, as many fresh- 

 air openings as convenient, each supplied with a regulator to direct the 

 air horizontally near the ceiling, the dimensions of these openings 

 being calculated so that the volume of air admitted may be increased 

 to six or eight times the total cubical capacity of the room, with an en- 

 tering velocity of but 2 or 3 feet a second. 



By means of these arrangements, drawing-schools may be made com- 

 fortable at night, which at present are almost like furnaces, and in 

 which it becomes necessary to open some of the windows even in winter, 

 notwithstanding the discomfort which may be experienced in conse- 

 quence by the scholars nearest to them. 



In the drawing-school just mentioned, the total amount of air carried 

 off every hour was : 



I 



