22

MODERN VIEWS ON VENTILATION.

(FROM OUR SPECIAL SANITARY COMMISSIONER.)I

Now that so many private dwellings, the public rooms of 1hotels, assembly rooms, riding schools, school rooms, andall kinds of commodious buildings, not constructed toserve as hospitals, are nevertheless receiving the wounded 1soldiers as they arrive from the front, the difficult problem (of ventilation has to be solved on a very large scale. This 1calls for all the more attention as of late years good cause {has arisen to shuw that principles which used to be generally (

accepted are no longer considered impeccable. At the beginning of the year an important account of the 7

most recent theories on the subject, and of some valuable Eexperiments, appeared in the Official Bulletin of the Inter- 3

national Office of Public Hygiene, having previously beenpublished in the Journal of the American Medical Associa- ;

tion. The publication has now been in the hands of thepublic health authorities of 32 governments for some little itime, and as sanitary reformers in these various countriesstudy the Bulletins of the International Office, we may hopethat modern teaching in regard to ventilation may becomewidely known. The care of :the wounded renders thisquestion of practical urgency at the present moment.

First, it is pointed out in the Bulletin that even beforethe discovery of oxygen the respired breath was believedto contain a noxious principle, and subsequently the evilwas attributed to carbonic acid gas. But at the beginningof the nineteenth century the presence of another poison incrowded and inefficiently ventilated rooms was suspected,and in 1851 Cavarret demonstrated that animals died when

placed in an overcrowded enclosure, though the excess ofcarbonic acid was withdrawn and oxygen supplied. Brown-

Sequard and d’Arsonval, after condensing the breath of menand dogs, and injecting this into animals, produced sym-ptoms of poisoning. Du Bois-Reymond said this had analbuminous base and called it " anthropotoxine." Thus thebelief in the direct contamination of air by breathing grew,involving the necessity of the constant removal and renewalof air. Nevertheless, so far back as 1842 Leblanc demon-strated that, no matter how crowded a room might be, theproportion of oxygen rarely fell to less than 20 per cent., and,on the other hand, Regnault and Reiset, only a few yearslater, showed that the proportion of oxygen could be reducedto 10 per cent. without increasing the rapidity of breathing.At the same time these and other authorities also demon-strated that air containing far more carbonic acid gas thancould possibly be found in the most crowded rooms mightbe breathed without causing any inconvenience. Pettenkoferlater on, in 1862, also insisted that it did not matter if the

proportion of oxygen in the air was decreased and that ofcarbonic acid increased. But though he denied that therewas any harm in even a large proportion of carbonic acid,its presence might become a good danger signal indicatingthat the atmosphere was likely to be infected. Many otherauthorities and experiments are mentioned in the Bulletln,all alike indicating how the belief that expired breath con-tained an organic poison was gradually abandoned. In1883 Hermans, of the Amsterdam Institute of Hygiene,attributed the discomfort and rising temperature from whichpeople suffer when crowded together in an ill-ventilatedplace not to poisonous atmosphere, but merely to the materialdifficulty caused by want of space. His simple explanationwas that persons in a crowd had not enough air around themto keep their bodies cool, the radiation from the skin of heatand their evaporating perspiration maintaining an excess oftemperature and humidity. He maintained that ventilationwas a physical rather than a chemical problem.

Professor Haldane, of Oxford, conducted various experi-ments during 1905, in a specially constructed chamber, incertain tin mines and weaving mills. He insisted that itwas the excess of dampness rather than of heat that wasinjurious. The same year Flugge, Heymann, Paul andErcklentz made comparative investigations with sick and

healthy subjects placed in a closed chamber. They did notsuffer when exposed to an excess of carbonic acid gas orwhen deprived of the usual proportion of oxygen, nor fromany volatile organic poison they might be supposed to expirefrom their lungs. But they did complain of the excess ofI) cat, of humidity, and the stillness of the air. For 30 yearsexperiments had been suggesting that neither carbonic acidnor some mysterious poison generated by the process of

breathing was the cause of the evils which ventilation is

expected to remedy, and at length the general observerturned to the physical rather than the chemical condition ofthe air as the thing which affects the individual. It became

recognised that we need movement and change in the air webreathe just as we need exercise and variety in the foodwe eat. Dr. Leonard Hill has made some important in-vestigations on these points. He has stated in our columnsthat the increased percentage of carbonic acid gas anddiminution of oxygen which have been found to exist in

badly ventilated enclosures are such that they can have noeffect upon the incidence of respiratory disease and higherdeath-rate which statistical evidence has shown to exist

among persons living in crowded and unventilated rooms.In his view it is the conditions of temperature, moisture, andstagnant atmosphere in such places which reduce the wholemetabolism of the body to a lower plane.

It used to be said that the air of an inhabited roomshould not contain more than 0-06 per cent. of carbonicacid. It is now demonstrated that when the carbonicacid does not amount to 1 per cent. it does no harm.Not more than 0’4 per cent. is found in the most over-crowded public halls. As for oxygen we know that mencan work and live vigorous healthy lives in the mountainousregions of the earth where the partial pressure of oxygen isonly 17 per cent. of an atmosphere or less. Much toomuch attention has been devoted to the effect pro-duced on the chemical composition of the atmosphere bybreathing, whereas the trouble is caused by the exhalations,the dampness and the heat coming from the body, its effectson the clothes worn and the temperature of the air surround-ing the body. What, therefore, is most important wheninquiring if a place is properly ventilated is to mark the

temperature and the degree of moisture. The proportion ofcarbonic acid, not important in itself, may also be noted asa witness of the quantity of fresh air supplied. If the resultis not good it is not reasonable to at once condemn the

system employed, whether it be some method of mechanicalventilation or natural ventilation depending merely on theopening of windows. Both these systems may work well orbadly according to the way they are applied, In a com-mercial establishment at New York, for example, where4000 persons are employed, the building was too hot. Therewas no fault to find in the system of heating and ventila-tion, but in its application. The flue that should havecarried away the heat from a warming apparatus to a venti-lating shaft was not in working order. Automatic recordingthermometers should be employed, especially in hospitals, asthe maintenance of the right temperature and degree ofmoisture is of the greatest importance to the patients. Butto obtain this result there is no general rule that can beuniversally applied. Every building needs its special systemaccording to its topographical position, the climate, the

prevailing winds, and many other conditions that vary fromplace to place.We are fairly safe in concluding that our powers of

resistance will be much greater if we feel at ease andnot over-exhausted physically. Our powers of resistancewill be affected if a draught is so cold or violent asto make us feel chilly and uncomfortable. This is a

very important phase of the question which, however,is not treated by the documents now published. It is

generally easy to obtain a large supply of fresh air bythrowing open a number of doors and windows ; but howcan the incoming current of air be so checked that it shallnot travel at a greater velocity than 3 feet per second ? Itis a false argument to say that wind travels at a much

greater rate and nothing is more healthy than outdoor life. Butwhen the wind is blowing we seek out a sheltered place beforesitting down. When moving we can tolerate and even enjoywhat we cannot endure when sitting still. The demonstrationmade that the air of an ill-ventilated place is not poisonoushas the practical result that it vindicates the use of the fan orthe punkah. Where we cannot get efficient ventilation wemay mitigate the evils arising by driving away the hot, dampair that surrounds us with a fan or a punkah. Formerly,while it was impossible to deny that this reduced our dis-

comfort, we doubted that it would save our health, for it didnot prevent our continuing to breathe over and over againthe same air. To-day we are told that this does not matter ;the quality of such air is not so seriously deteriorated as weused to believe. Therefore, and particularly as the summerheat increases, it is something to know that the fan, theelectric fan, or the punkah serves a useful purpose.