WAEMING AND VENTILATING OCCUPIED BUILDINGS. 



Classification of heating-apparatus in regard to heating effect. 



Forms of apparatus. 



Ordinary flre-places — 

 Ventilating fire-places 



Common stoves, j Cast iron, burning j Q°?g' 

 without circula-^p^^^gi^^j^ ^j^r^jj^^^oj,^^ 

 tionotair. [ slightly healthful ..... . 



Metal stoves, with f Model in use in schools 



circulation of air J in Paris 



taken from the [With vertical pipes, 

 outside or inside. I. Chaussenot's model 



Heaters with pipes f Horizontal . 

 ho't aS °^ I Vertical ... 



Apparatus for cir- 

 culation of hot < 

 water. 



When the pipes and radi- 

 ators are very numer- 

 ous with large suri'ace 

 compared with that of 

 the heater 



When the boiler, furnace, 

 and all the radiators or 

 pipes are contained in 

 the place to be warmed. 



3 » o 



QJ O O 



10-12 

 33-35 



93 



65-75 



Eemarks. 



Carry off foul air but do not directly bring in 

 fresh air. Effect of system healthful. 



Carry off foul air and directly introduce mod- 

 erately warmed fresh air. Healthful system 

 of heating. 



I Produce a very insuflScient change of air. 

 I Unheal thful system. 



■j Do Hot produce sufficient change of air and 

 heat too much the air they introduce. Very 

 injurious system of warming if pipes be of 

 cast iron; slightly healthful if of sheet iron. 



] Cannot directly produce a sufficient removal 

 of foul air and in general supply over- 



! heated air, but may easily be modified so as 



I to give out air at 86° or 104°. System in- 

 jurious when not combined with means of 

 ventilation. 



Easily adapted for the establishment of reg 

 (' ular direct ventilation. 



VENTILATION 



GENERAL PRINCIPLES. 



31. Properties of air. — Before giving the rules to be followed and tbe 

 proportions to be adopted to secure in dwellings a proper change of air, 

 it will be useful to state some general principles of physics relative to 

 the properties of this gas. 



Air, composed of 21 per cent, of oxygen and 79 of nitrogen, is a pon- 

 derable body. At the temperature of 32°, and under the pressure of 

 30 inches of mercury, 1,000 cubic feet of air weigh 1-^ ounces. It is subject, 

 then, like all other bodies, to the laws of gravity. Its molecules, like 

 those of all gases, are but feebly bound to each other by molecular 

 attractions; the slightest force, the least elevation of temperature, the 

 feeblest reduction of pressure, causing the preponderance of the repul- 

 sive forces and separating the elements from each other. On the contrary, 

 the slightest depression of temperature unites more closely the mole- 

 cules of air, and renders it more dense and heavy. 



Air expands under the action of heat and contracts under that of 

 cold, the same as other gases, and its volume varies with the tempera- 

 ture, according to Gay-Lussac's law, expressed by the formula — 



Y=[ 1 + 0.002036 (^-32) ] Yo=[ 1 + a {t—32) ] Vo 

 in which— 



Vo=its volume at 32°, and at the barometric pressure of 30 inches 

 of mercury. 



