Vol. XI. No. 269. 



THE AGRICULTURAL NEWS 



SOME CONSIDERATIONS REGARDING 

 VENTILATION. 



The subject of \eniilation is treated in an original 

 manner in a paper read recently liefore the Royal Society of 

 Arts, the authors being Leonard Hill, M.B, F.ll S., and 

 Martin Flack, M.A., il.i!., B.Ch. It was printed, with the 

 discussion, in the Journal <if the. Roi/al Society of Arts for 

 February 9, 1912. 



The paper commences by pointing out that, though the 

 good effects following efficient ventilation and open-air treat- 

 ment are generally attributed to the chemical purity of the 

 air, they are due really to the: 'movement, coolness, relative 

 humidity of the air, and to the ceaseless variation of these 

 qualities.' The ventilating engineer and the heating engineer 

 have sought to make conditions more comfortable, the first 

 by the supply of chemically pure air, the second by heating 

 the air to a uniform temperature; whereas their real aim 

 should be to provide air: 'which is cool, of proper relative 

 humidity, and which moves so as to vary the cutaneous 

 state of the body,' 



In considering the chemical purity of the air, three 

 matters may be kept in view: the concentration of carbon 

 dioxide, the concentration of oxygen, and the supposed exhala- 

 tion of organic poison in the breath. As regards the first, 

 from the fact that the percentage of carbon dioxide in the 

 air of factories must be kept exceedingly low, it is the general 

 idea that the presence of the gas in any proportion greater than 

 that percentage causes the air to be poisonous. Actually, the 

 truth of the matter is quite otherwise, and this is easy to see 

 when it is considered that the percentage of carbon dioxide 

 in the air of the lungs is always about five — a percentage 

 very much higher than the amount that it is not legally 

 permissible to exceed. It follows that it is impossible for 

 a person to breathe more carbon dioxide than is good for him, 

 even in the worst ventilated room. Examples are given, 

 further, to show that in nature the movements of animals, and 

 the postures in which they rest, are governed by considerations 

 of warmth and moisture of the air, and not by the circum- 

 stance of the percentage of carbon dioxide that it contains. 

 Evidence in the same direction is also adduced from the 

 fact that workers in breweries, divers in diving dresses, and 

 those who work in compressed air caissons, where the per- 

 centage of carbon dioxide is always comparatively high, do 

 not suffer from this condition. 'It results, then, from 

 what we have said, that concentrations of carbon dioxide, 

 such as occur in the most crowded and worst ventilate<l 

 rooms, are of no account.' 



It is convenient now to discuss ventilation in regard to 

 the percentage of oxygen in the air. As is stated in the 

 paper, the oxygen in the worst ventilated school-room, place 

 of worship, or theatre, is never lessened by more than 1 per 

 cent, of an atmosphere. Attention is drawn, again, to the cir- 

 cumstance that the concentration of oxygen in mountain 

 health resorts, and in the towns on the high plateaux of the 

 Andes, is reduced to a much greater amount than this, and 

 yet the visitors and inhabitants do not suffer in any way from 

 this cause. Further, experiments have been made in which 

 persons have been confined in an air-tight chamber in which 

 the oxygen was gradually reduced to about 16 per cent., and 

 there was 3.V per cent of carbon dioxide present, when no dis- 

 comfort was suffered by them although the proportion of 

 oxygen in the air was too low to enable them to light 

 a match and smoke a cigarette. Investigations of the kind 

 have shown that it is only when the oxygen is reduced below 

 a pressure of H to 1.5 per cent, of an atmosphere that 

 signs of its want appear. 'A diminution of 1 per cent, of 



an atmosphere has not the slightest effect on our health t 

 comfort.' 



As it is must be concluded that ventilation is required 

 neither to take away carbon dioxide nor to restore oxygen, the 

 third of the causes mentioned above, of discomfort in crowded 

 places, \\\s, been adduced, namely the presence of organic 

 ehemieal poisons that have come from the human breath — 

 poisons whose presence is said to be proved by the exis- 

 tence of the smell or 'fugg' in such places. In actual circum- 

 stances, those inside the room, helping to make the 'fugg', ar; 

 unaffected by it, while it is only those who enter from outside 

 who are likely to remark it. Examples are given which show 

 decisively that, in general, the dislike of a smell arises 

 rather from its unaccustomed nature than from any pois- 

 onous quality. In a more exact way, the supposed exi->- 

 tence of organic chemical poisons in expired air is based 

 upon experiments of Brown-Sequard and d'Arsonval, 

 who injected into guinea pigs and rabbits either 

 water condensed from the breath or water that had 

 been used several times to wasa out the windpipes 

 of dogs; when the animals showed signs of illness, collapse 

 and death, < )ther investigators, among whom are those 

 possessing the best methods of work, have not confirmed 

 these results. It seems that the injected water contained 

 traces of the proteins of the saliva, so that an anaphylactic 

 shock was produced in the animals after a second injection; 

 this means that the animals had become sensitised by the 

 first injection, and were therefore [loisoned by the subsequent 

 injection of the proteid, which was foreign to them, in the 

 saliva. Confirmalif.m of the supposed poisonous nature cf 

 breath has been alleged to have been obtained by the injec- 

 tion into a mouse of 1 or 2 c,c. of condensation water 

 obtained by breathing through a cooled flask. As tha 

 mouse weighed about i;5 grams , this was equivalent to 

 injecting about 9 pints of water into a man weighing just 

 over 140 &., so that small wonder may be felt that the 

 animal became ill. The experiment with the mouse is dis- 

 credited further by the fact that the same symptoms may 

 be produced by injecting a similar quantity of pure water 

 alone, 'Such experiments are ridiculous, and deserve not 

 a moment's attention.' After dealing further with the 

 matter, the authors proceed to say: 'After studying the 

 literature on this subject we are convinced that there is no 

 positive evidence which demonstrates the poisonous nature of 

 the condensation water obtained from the breath. We go 

 further and say there is at present no trustworthy evidence 

 of the existence of any such poison in the exhaled air.' 



The real cause of discomfort in crowded rooms arises in 

 the following way. The air actually in contact with the 

 bodies of the persons in the room is confined by the clothes 

 and becomes almost as warm as the body, and saturated 

 with moisture, so that perspiration, wetness and flushing 

 of the skin, and a rise of its temperature, are brought about. 

 Under the conditions, the blood is kept near the outside of 

 the body, and does not pass in proper proportion through 

 the brain and internal organs. On the other hand, the 

 feelings of discomfort and fatigue do not arise if this 

 'blanket of stationary wet air' is prevented from forming by 

 causing a proper amount of movement of the air, by fans 

 or otherwise. 



The paper presents an account of many interesting 

 observations in support of the supposition that discomfort 

 is caused by excessive heat and humidity of the air, and not 

 by excess of carbon dioxide or want of oxygen, and concludes 

 by making valuable suggestions as to the use of ozone for 

 improving conditions where there is not free natural move- 

 ment of the air. 



