WARMING AND VENTILATION. 



287 



All these arrangements, carefully planned in advance by M. Laval, 

 and carried out as the building progressed, have cost but $5,000 for the 

 complete purification of all the occupied parts of a school of three hun- 

 dred scholars, which, estimating the interest on the cost and the wear 

 and tear at 10 per cent,, amounts to but $500 a year, or $1.67 a scholar. 



There can be no doubt that in such an establishment the health and 

 the vigor of the youth, by reducing the number of sick days, would 

 compensate largely, even in an economic consideration, for expendi- 

 tures so well made. 



It is, however, proper to remark that in winter the temperature may 

 fall unusually low at Toulon, and that ventilation without heating may 

 prove unpleasant. It would be easy to comjilete the beginning thus 

 made by adding a few heaters. 



WORKSHOPS. 



68. During the day, it is usually sufficient to change the air two or 

 three times an hour, according to the general rules given in § 38 and 

 following. 



If substances iiroducing disagreeable or nnhealthful odors are pre- 

 pared or used, it will be advisable, if possible, to separate the sources 

 of infection by partitioning off compartments almost as tight as drying- 

 chambers, and carrying off the emanations by a strong local draught, 

 carrying them under the floor and thence into a main ventilating-chim- 

 uey, (Fig. 20.) 



The fresh air brought in near the ceiling, and which should be hot or 



cold, according to the season, de- 



scends in the rooms, and con- 

 stantly renews that of the com- 

 partment, which is drawn off 

 without being able to spread 

 into the room itself. 



If there are many places where 

 the unhealthful materials are 

 used, and they are scattered over 

 almost the whole surface of the 

 workshop, it would be advisable 

 to place near each workman a ventilating-openiug, communicating with 

 collecting-pipes terminating in a common ventilating-chimney. 



The amount of air carried oft" in this way should be greater the more 

 dangerous the materials are to breathe. It is then necessary that the 

 air of the shop be changed at least three or four times an hour, and in 

 some cases, such as in match-factories and other unhealthful works, it 

 should be done eight or ten times. 



[ In shops lighted by gas, and where every workman has a separate 

 gas-burner, the products of combustion may often be readily removed 





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