VENTILATION. 201 



VENTILATION. 



We may define ventilation as the process of removing 

 foul air and substituting for it pure air in a building. 



The subject of ventilation is closely connected with that 

 of drainage ; for inefficient drainage often entails a bad state 

 of ventilation. Thus, an amount of ventilation which 

 would be amply sufficient if a stable was kept scrupulously 

 clean, might be much below a healthy standard, if the air 

 was exposed to foul emanations from decomposing organic 

 matter. For practical purposes we may take for granted that 

 the ventilation cannot be good, if the drainage is defective. 



We have seen that in a climate as cold as that of England, 

 horses should be shielded from draughts in the stable. 

 The question of obtaining free circulation of air in a 

 building, without draughts, brings us to the definition of a 

 draught. Although we cannot determine with exactness 

 when a draught ends and safe ventilation begins, it will 

 suffice for every-day needs if I say that a draught is a 

 current of air which is appreciable to our sense of feeling 

 under ordinary conditions. Hence, to save our horses from 

 chill, and at the same time to give them a full supply 

 of fresh air, we should arrange the ventilation of the stable 

 in such a manner, that the force of in-coming currents of 

 air is broken and distributed, while the entrance and exit 

 of the air is checked as little as possible. The dangers arising 

 from the retention in the atmosphere of the stable, of 

 volatile and floating impurities (products of decomposition, 

 bacteria, etc.), are too well known to need my dwelling on the 

 necessity of their speedy removal by well regulated ventilation. 

 If the source of these deleterious matters is allowed to remain 

 for a considerable time in the stable, it will be impossible by 

 any system of ventilation to keep the air even approximately 

 pure. Our object, however, will be fully attained, if we are able 



