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.

    167/610 (page 155)
    CHAPTER VI. BUILDINGS. Most of the ordinary building materials are pervious to air and water to a greater or less extent. Galton states that with a temperature of 40° F. outside, and 72'^ F. within, the volumes of air passing through a square yard of wall vary according to the material, as follows :— cubic feet per hour. Sandstone . 4-7 Quarried Limestone . 6-5 Brick . . 7-9 Limestone . 10-1 Mud . . 14-4 The thickness of the wall is supposed to be the same in all cases. Mortar, cement, and concrete are also permeable, and the caustic lime they contain absorbs carbonic acid until it becomes saturated. Wood in its natural condition absorbs water, and the inevitable joints and crevices admit of the passage of air and water. By painting, varnishing, and other means the inner surfaces of walls, floors, and ceilings can be ren- dered impervious, and walls lined with glazed bricks or the finer cements (Parian) are scarcely permeable. The disadvantages of porous materials are obvious, and the air admitted in this way is insignifi- cant in amount and at least doubtful in purity. Pervious walls are liable to be damp and cold. Air passing through them in either direction is filtered, and the wall becomes charged with organic impurities. This is specially the case with the inner surfaces, and in hospitals it is now customary to render the walls and floors impervious as far as possible. The exclusion