In dealing with the subject of ventilation in any form, it is necessary to touch upon elementary facts, which are applicable to whatever class of building or place it may be required to ventilate, yet anything like a detailed description of the special and more complicated methods which may be required for public buildings and institutions, or for factories, is beyond the scope of this work, and will not be attempted. The object of this section of the book is to place before architects, builders, students, and householders, such a view of the subject as will enable them intelligently to comprehend the possibilities of securing efficient ventilation in our British homes; for, although the principles are the same the whole world over, there are in some regions climatic conditions and national customs which require distinctive consideration and treatment. It is, however, undesirable herein to (-(implicate the subject by discussing such special and somewhat exceptional demands.

Important as it may be that every architect and builder should have a clear conception of what can be done to provide for efficient ventilation throughout a dwelling, and that they should apply such knowledge in a practical manner, it is even more essential that every householder should understand the limits to the power of an architect or builder to make provision for ventilation under varying conditions of the atmosphere, and in the various apartments of a dwelling, and that he should also realize the necessity for constant supervision and regulation, even when the greatest care and knowledge have been employed in providing suitable means for ventilation.

Section XII - Ventilation By William Henman

Architect Fellow Of The Royal Institute Of British Architect; Past Prerident Of The Birmingham Architectural Association

Nothing has been more fruitful in developing erroneous notions upon the subject of ventilation than the employment of unscientific terms in connection therewith, such as Automatic Ventilation. Ventilation, by whatever means it is induced, is the result of certain agencies or forces, either natural or mechanical, but never automatic. Natural means may be employed, or mechanical mean, to secure ventilation, but with neither must it for a moment be supposed that the action is automaic. This question of terms, which is of the utmost importance to a proper understanding of the subject, is now simply mentioned as a precaution before defining what should be understood by the term "Ventilation Ventilation is far more than providing for change of air. Most people, if asked what is implied by the term Ventilation, would answer - Change of air. This is true so far as it goes, but becausc it is only a portion of the truth, the answer is, to say the least. misleading. This can be easily proved by throwing open the windows of a crowded and overheated room on a cold and windy night. Change of air may quickly be procured, hut certainly not the efficient ventilation of the apartment, because discomfort to the occupants would cer-tainlv result. In occupied rooms, something more than mere change of air is neceasarv to secure good ventilation, for, although in the abstract ventilation is one and the name, it may be qualified in degree, and therefore it is ever neces-aarv to enlarge on several elementary facts, which must be clearly borne in mind and taken into account whenever an apartment has to be ventilated, or when means have to be devised whereby a whole building, consisting of several apartments of varying size and employed for various purposes under varying condition-, has to be ventilated; and in addition to these elementary facts, there are influences at work of a more subtle nature, some of them as yet but imperfectly understood, which nevertheless should be examined, so that they may be encouragcd or counteracted as required.

It is more particularly with respect to the physical properties of the atmosphere, and its effects upon human existence, that our subject is concerned, and consequently it must be clearly grasped that, apart from exceptional or acei-dental circumtances, -

1. life1 is only sustained when atmospheric air can be freely breathed. 2.To sustain healthy life, air must be pure and uncontaminated.

3. Vitality will be impaired, either temporarily or permanently, of air be breathed which is contaminated or is below the normal state of purity, in proportion to the time during which it has been breathed and the degree of its impurity

Air is not necessarily pure even in the open and apart from human agencies.

1 Human life is particularly referred to, but the statement applies to most living creatures in the higher of existance; conecquently much that applies to the ventilation of buildings erected for human habitation, will also apply to stables, farm-buildings, kennels, aviaries, etc.

5. It is, however, more frequently contaminated by human agencies.

6. When air is allowed freedom to circulate, there are many processes at work by which it is maintained at almost uniform composition, and by which it is purified after contamination.

7. When inclosed within a building, it may be quickly contaminated from a variety of causes.

These are the principal reasons why ventilation is necessary, and why it should be intelligently induced; they will therefore be enlarged upon: -

1. The action of respiration, which continues so long as life is sustained, alternately supplies air to the lungs and expels it therefrom. The lungs, being of thin membranes formed into innumerable small cells or vesicles, which by muscular action of the body are expanded, suck in air by the bronchial tubes and windpipe, through the nose and mouth, and then, when the muscular action is relaxed, they contract and expel the air, which, however, has in the meantime been brought into very intimate contact with the blood circulating throughout the large extent of lung tissue, and has undergone a considerable change in composition and temperature, a change by which air is undoubtedly contaminated, and made less capable of sustaining a healthy existence, particularly when confined within buildings.