. Preventive medicine and hygiene. able, then comes brick,then sandstone, next plaster of paris, while enamel and tile are im-pervious. Under a pressure of 108 millimeters of water the followingamounts of air pass in one hour through one square meter of: Mortar 3,264 liters Plaster of paris 146 Bricks 312-1,396 Sandstone 426- 496 A pressure of 108 millimeters of water is equivalent to the pressureof a strong wind. The amount of air that will pass through porousmaterials varies, of course, with the temperature, moisture, and otherfactors. Marker and Schultze, in their resea:rches on the spontan
. Preventive medicine and hygiene. able, then comes brick,then sandstone, next plaster of paris, while enamel and tile are im-pervious. Under a pressure of 108 millimeters of water the followingamounts of air pass in one hour through one square meter of: Mortar 3,264 liters Plaster of paris 146 Bricks 312-1,396 Sandstone 426- 496 A pressure of 108 millimeters of water is equivalent to the pressureof a strong wind. The amount of air that will pass through porousmaterials varies, of course, with the temperature, moisture, and otherfactors. Marker and Schultze, in their resea:rches on the spontaneous ventila-tion of stables, found that the following interchange of air occurredper hour over one square yard of free wall at ° E. difference oftemperature: With walls of sandstone cu. ft. Quarried limestone Brick Tufaceous limestone - Mud « It is possible to force suflficient air through an ordinary brick todeflect the flame of a candle on the other side. This demonstration 760 VENTILATION AND HEATING. Fig. 93.—Window Ventilator. is usually accomplished by coating the edges and exposed portions ofthe brick with sealing-wax and arranging on either forced with a bellows through one funnel may be measured eitheras to its amount or velocity as it comes out of the opposed funnel. Natural ventilation is better in winter than in summer, owing togreater differences in temperature. It may he almost nil on a hotcalm day. Too much moisture in the air of a room settles upon thesurfaces and thus stops the pores of building materials, and also prevents the escape of carbondioxid. Eain has a sim-ilar effect on the out-side. An ordinary brick^^ill soak up a pint ofw a t e r. Ventilationthrough the walls isalso hindered by oil andenamel paints and byA^ all-paper. Outside ob-stacles, such as exces-sive foliage and nar-row streets, are alsoconsiderable ventilation may be greatly favored by simple devices. Thismay be demonstrat
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Keywords: ., bookauthorwh, bookcentury1900, bookdecade1910, booksubjecthygiene
