ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
103 
In reference to the above standards the following remarks are necessary :— 
(1.) The above limits for houses apply more particularly to sleeping-rooms. 
(2.) It has been considered necessary to allow a somewhat higher limit for carbonic 
acid in schools than in dwelling-houses. The reasons for this are :—( a ) The quantity 
of carbonic acid produced by respiration during waking hours is greater than when 
asleep, and it is therefore more dithcult to maintain so low a standard in the former 
case. # ( b) The average cubic space per person is at present considerably less in 
schools than in even one-roomed houses, (c) The examination of 68 different school¬ 
rooms, 30 of which were considered to be sufficiently well ventilated, shows that, even 
when ventilated mechanically by fans, an upper limit of 13 vols. per 10,000 (or 9 vols. 
in excess of outside air) is as low a one as we could reasonably expect not to be 
exceeded. We are fully of opinion, however, that the limit should not be fixed 
higher. The data on which the above opinions are based will be seen from the foot¬ 
note on page 102. 
(3.) The upper limit of 10 vols. per 10,000 for dwelling-houses (especially in sleeping- 
rooms) is the one which is usually adopted by most authorities, and this we can 
fully confirm. Wilson (‘Handbook of Hygiene/ and quoted in Parkes, p. 115) 
states that in cells (in Portsmouth Convict Prison) of 614 cubic feet, always occupied, 
he found 7 ‘2 vols. of carbonic acid, and that the prisoners inhabiting these cells were 
healthy and had a good colour. In cells of 210 cubic feet, occupied only at night by 
prisoners employed outside during the day, he found 10'4 vols. of carbonic acid. The 
occupants were all pale and ansemic. 
De Chaumont (‘ Poy. Soc. Proc./ vol. 23, p. 187) gives 6 vols. (or 2 vols. in excess of 
the outside air) as the maximum amount of carbonic acid admissible in a properly 
ventilated space. He believes that an atmosphere ceases to be good when the 
carbonic acid reaches 8 vols. (or 4 vols. in excess) ; that it becomes decidedly bad 
when the carbonic acid reaches 10 vols. (or 6 vols. in excess); and that it becomes 
very bad when 12 vols. (or 8 vols. in excess) is reached. Though it would be very 
desirable, could this lower limit be maintained, yet from our own investigations it 
seems to be practically impossible, in schools at least, without involving too great 
a cost or using an extensive “ open window ” ventilation. The latter would be very 
objectionable, and quite inadmissible in winter. The standards proposed above are 
practical, and may be attained without draught, so that we may reasonably expect 
and demand that the air of dwellings and schools should be maintained within the 
limits of purity assigned above. 
The lower limit for carbonic acid, proposed by De Chaumont, is based as follows 
(‘Poy. Soc. Proc./ vol. 23, p. 187):—(1) That the air of a room should be maintained 
in such a state of purity that a person coming directly from the external air should 
* Pettenkofer found tliat in repose a man of 28 years evolved at night, when asleep, '56 cubic foot of 
carbonic acid, and '78 in the day-time, with very moderate exertion 
