Hygiene and public health / by B. Arthur Whitelegge.

  • Arthur Whitelegge
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Hygiene and public health / by B. Arthur Whitelegge. Source: Wellcome Collection.

    45/610 (page 33)
    Open Fires, The advantages of artificial ventilation are its constancy under all conditions and the faciHties which it aftbrds for regulating the source of fresh air, the volume delivered and the preparatory treatment as to temperature, moisture, and purification. Natural ventilation is, of course, less costly, but is incon- veniently subject to atmospheric conditions, and is inadequate as regards theatres, schools, and other crowded buildings. Carnelley, Haldane, and Ander- son have proved this experimentally. A comparison was made between the results of natural and artificial ventilation of schools. The following averages, based in every case upon many observations (18 to 39), are conclusive evidence of the superiority of mechanical ventilation. Per cent, of windows open . Cubic feet of air space, per head Temperature (Fahrenheit) Carbonic acid (per 1,000 vols.). Organic matter (vols, of oxy- gen required per mil- lion vols, of air) . Microbes (per litre) Natural Ventilation, 22 168 55-6° 1-86 16-2 152 The difference is still more striking if only the excess over the impurities present in outside air is taken into consideration. It was found that mechanical ventilation kept the composition of the air fairly con- stant in all parts of the room, while natural ventilation often allowed of local stagnation. In an ordinary room the chimney is the most important outlet when a fire is burning, air passing up with an average velocity of 4 or 5 feet per second. D—28