ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
79 
Schools. 
Naturally ventilated. 
Mechanically ventilated. 
No. of 
cases. 
Lowest. 
Highest. 
Average. 
Average. 
Lowest. 
Highest. 
No. of 
cases. 
Per cent, of windows open . . 
22 
3 
No. present, including staff . . 
39 
27 
191 
92 
64 
20 
170 
20 
Space per person. 
39 
56 
427 
168 
164 
119 
228 
20 
Temperature (° Fahr.) .... 
35 
44 
65 
55-6 
62 
58 
69 
18 
Carbonic acid. 
39 
7'9 
37-8 
18-6 
12-3 
70 
19 6 
20 
Organic matter. 
38 
5-0 
40-3 
16-2 
lO’l 
3'4 
19-0 
20 
Total micro-organisms :—■. . . 
35 
8 
600 
152* 
16-58* 
0 
58 
18 
Bacteria. 
28 
8 
600 
151 
16-0 
0 
56 
18 
Moulds. 
28 
0 
4 
1-1 
0-58 
0 
2 
18 
Or above outside air :— 
Temperature (° Fahr.) . . . 
25 
3 
34 
16-8 
24 
22 
26 
3 
Carbonic acid. 
39 
4-4 
343 
15-1 
8-9 
3-5 
16-1 
20 
Organic matter. 
38 
0 
31'4 
7'8 
1-1 
0 
53 
20 
Or, if we take as units the average cubic space, the average excess over outside air 
of temperature, of carbonic acid, and of organic matter, and the average micro¬ 
organisms, in mechanically ventilated schools, the comparative results for naturally 
ventilated schools may be expressed as in the following Table 
Mechanically ventilated. 
Naturally ventilated. 
Cubic space per person. 
1 
1-0 
Temperature in excess of outside air . 
1 
0-66 
Carbonic acid „ ,. 
1 
1-7 
Organic matter ,, ,, 
1 
7-0 
Micro-organisms ,, „ 
1 
9-2 
Bacteria „ „ 
1 
9'4 
Moulds ,, ,, 
1 
2-0 
The above Table shows that with mechanical ventilation, the space per person being 
the same :—(1) The carbonic acid was three-fifths, the organic matter one-seventh, 
and the micro-organisms (see pp. 96, 97-98) less than one-ninth of what they were 
in schools ventilated by ordinary methods. (2) That, notwithstanding this very great 
improvement in the purity of the air, the temperature is very considerably higher in 
the mechanically ventilated schools. 
To produce such improvement in purity by the ordinary methods of opening 
windows, &c., would have reduced the temperature to a very uncomfortable and 
dangerous degree. The improvement is also obtained with comparatively little 
* The marked difference between these two classes of schools is shown still more distinctly by the 
fact that of the mechanically ventilated schools only two contained more than 26 micro-organisms per 
litre, whereas of the naturally ventilated schools only three contained less than 26 per litre. 
