



332 SECTION MECHA NICS. 



NECESSARY CUBIC SPACE AND QUANTITY OF AIR. 



Important studies were made in 1842 by M. Leblanc, a French 

 physician, under the title of Investigations upon the composition of air 

 in enclosed places j the conclusion to which he came may be expressed 

 as follows : 



The proportion of carbonic acid increases according to the degree of 

 unhealthiness (of the locality) and may be taken, so to speak, as its 

 gauge. 



In a note entitled: On the Citbic Space and volume of air, necessary 

 to insure the healthiness of inhabited places, Dr. Chaumont, an 

 English army doctor, has given a Table of comparisons between the 

 proportions of carbonic acid and the impressions on the sense of smell. 



He has proved that a bad smell, indicating unhealthiness, manifests 

 itself, as soon as the proportion of carbonic acid in the air is greater 

 than 0*0006. 



I found it easy to deduce from it the volume of air which ought to be 

 renewed according to the cubic capacity of the inhabited places. Here 

 are the results : 



Cubic space for each person : 



M.C. I M.C. I M.C. I M.C. I M.C. I M.C. I M.C. I M.C. 

 10 I 12 I l6 I 20 30 I 40 50 60 



Volume of air to be introduced per hour and for each person : 



M.C. I M.C. I M.C. I M.C. I M.C. I M.C. I M.C. M.C 



90 I 88 I 84 | 80 I 70 I 60 I 50 40 



These figures agree with the practical rules adopted by French and 

 English engineers. 



INFLUENCE OF THE EXTERNAL TEMPERATURE. 



The fundamental condition of the uniformity of the "appel" is that 

 the temperature in the escape-chimney should always be equally greatei 

 than that of the external air. A difference of 2oc is generally sufficient 

 Natural ventilation has the inconvenience of being subject to acciden- 

 tal distubances in its motions and consequently is inadequate to ensure 

 healthiness. 



The application of the preceding principles has given the results 

 summed up below. 



Creche de St. Ambroise a Paris. (Day nursery for babies). This 



