The effect of impure air in its action on the heart is thus spoken of by Dr. Cornelius Black:  “I showed the effect of impure air in promoting the degenerative tendency in the structures of the heart, and especially those of the right side of the heart, after the age of forty.  I was then led to a passing consideration of the baneful influence produced upon the heart by badly-ventilated houses, schools, manufactories, pits, theatres, underground railways, and all places of a similar character.”  “The impure atmosphere of the bedrooms of the poor, and indeed of many of the middle class, caused by deficient ventilation, proves a sharp spur to the degenerative tendency manifested by the heart, and especially by the right side of the heart, after the age of forty.”  “I hold that the breathing of impure air is a fruitful source of disease of the right side of the heart occurring after middle age.  How many people ignorantly favour its occurrence by confining themselves to closely shut, non-ventilated, stuffy, sitting rooms, in which the carbonic acid has accumulated to a poisonous degree in the air they respire!  How are these evil results to be prevented?  The simple answer is, let the rooms in which you live be effectively ventilated by an incoming current of fresh air, and so arranged that no draught shall be felt.”

Sanitarians who have devoted a good deal of time and study to the working out of questions relating to the amount of fresh air in bedrooms have decided that each person should, if possible, have at least 1,000 cubic feet of space, or in other words, the same amount contained in a room 10 feet long, 10 feet wide, and 10 feet high.  It is also estimated that the amount of fresh air entering into a room of this size should be 3,000 cubic feet per hour, that is, the air in each room should be completely changed three times every hour.  These observations of course apply only to the least amount of air which every sleeper is strictly entitled to.  As a matter of fact, however, any more than this is simply of distinct advantage as far as health is concerned.  The bedroom, instead of being the smallest room in the house, as it too often is, should be really the very largest.  Now it has been previously stated that foul or vitiated air collects in a sleeping apartment unless there be a continuous circulation of fresh air; and that the noxious exhalations from the breath and skin constitute the chief sources of air pollution.  The practical point to discover is how to have this continuous circulation of fresh air throughout the room without causing a draught.  Before considering this, a few words on the position of the bed itself will possibly be appropriate.  It is always better to have it standing more in the centre of the room with its head against the wall, than to have it jammed alongside the latter.  And it certainly should have placed north and south if the shape of the room admits of it.  The wire-wove mattress is of great advantage both for comfort and for coolness; and here in Australia, during the summer months, proper mosquito nettings are as necessary as the bed itself.  If the bed is provided with a head-piece, as it should be, there is no difficulty in fitting on the netting.