RENEWAL OF THE AIR IN LIVING-ROOMS. 247 



that makes the air of crowded spaces injurious, but rather the exhalations from 

 the outer and inner surfaces of the body, which at the same time render the air 

 offensive to the sense of smell, still the amount of carbon dioxid is an indication 

 of the degree of vitiation of the atmosphere. To determine whether or not the 

 ventilation is sufficient in spaces crowded with individuals, the carbon dioxid of 

 the air should be estimated quantitatively at the time of occupation; hence, in 

 school-rooms, if possible, shortly before the close of the school-session , or in sick- 

 wards or dormitories (barracks) shortly before daybreak. As a good, comfortable 

 room-atmosphere contains less than 0.7 of carbon dioxid in 1000, the ventilation 

 of a space must be considered insufficient if more than i.o in 1000 is found. 



The atmosphere contains only 0.0005 cubic meter of carbon dioxid in i cubic 

 meter of air, and an adult produces hourly 0.0226 cubic meter of carbon dioxid. 

 Therefore, it will be found on calculation that ventilation must supply 113 cubic 

 meters (for a child 60 cubic meters) of fresh air hourly for each person if the carbon 

 dioxid in the living-room is to be kept below 0.7 in 1000 0.7 : 1000 = (0.0226 -f 

 x X 0.0005) : x ' hence, x = 113. If the amount of carbon dioxid in the air of a 

 room be allowed to reach i.o in 1000, then an hourly ventilation of 45 cubic 

 meters is sufficient for an adult, and 24 cubic meters for a child. 



The following method is employed to determine whether a living-room has 

 sufficient ventilation. A large quantity of carbon dioxid is generated in the 

 room, as much as i or 2 liters hourly for every cubic meter of space. The burning 

 of stearin-candles may be employed as the source of carbon dioxid, each candle 

 producing 12 liters of gas in one hour; a gas-burner supplies 100 liters an hour; 

 an adult man produces 22.6 liters by respiration, and a school-child 12 liters 

 hourly. If sufficient carbon dioxid has been produced at the end of an hour, the 

 generator is removed, and the first estimation of carbon dioxid in the air is made, 

 according to the method described later on. At the end of another hour, during 

 which the windows and doors are kept closed, the second estimation of carbon 

 dioxid is made. The amount of fresh air that has entered by ventilation during 



this hour is calculated by the following formula: C = 2.3 X m X log. - --*, in 



which C represents the volume in cubic meters of fresh air that has entered by 

 ventilation in one hour, m the volume of room-space in cubic meters, p the amount 

 of carbon dioxid contained in i cubic meter of the air in the room at the first 

 estimation, expressed in cubic meters, q the amount of carbon dioxid in each 

 cubic meter, found at the second estimation and expressed in cubic meters, a the 

 carbon dioxid in atmospheric air = 0.0005 cubic meter in i cubic meter of air. 

 Example: In a school-room, containing 40 children, the first estimation of car- 

 bon dioxid is made shortly before the close of school. If the result be 2 in 1000, it 

 will indicate the presence of 0.002 carbon dioxid in i cubic meter of air. After 

 the children have gone, the windows and doors are again closed, and the second 

 analogous estimation is made at the end of an hour. If the result be i in 1000, 

 there will be o.ooi carbon dioxid in i cubic meter of air. The size of the school- 

 room is 600 cubic meters. The quantity of fresh air that has entered the space 

 during the hour can be estimated according to the foregoing formula: C = 2-3X 



600 X log. 0.002-0.0005 = I3 8oX log. ^^ = 1380 X log. 3 - 1380 X 

 o.ooi 0.0005 0.0005 



0.4771213 = 658.3 cubic meters. Hence, 658.4 cubic meters of fresh air have 

 entered the school-room by ventilation. As one child requires 60 cubic meters of 

 fresh air hourly, the 40 pupils require 40 X 60 = 2400 cubic meters of fresh air 

 in one hour; but, as a matter of fact, the ventilation of this space amounts to 

 only 658.4 cubic meters; therefore, 1741.6 cubic meters are still wanting. Hence, 

 either a better ventilation must be provided, or fewer children should be allowed 

 to attend the school. A ventilation that amounts to more than three times the 

 room-space hourly will be found to give rise to an unpleasant draft, and is, there- 

 fore, often directly harmful in winter. For the school-room in question containing 

 600 cubic meters of space, only 1800 cubic meters of ventilation hourly would be 

 permissible; hence, there is only space in that room for at most 30 pupils (30 >< 

 60 = 1800). As the space receives only 658 cubic meters of ventilation hourly, 

 provision must be made by better ventilation for the addition of 1 142 cubic meters 

 more of fresh air; but without further ventilation place could be found in the 

 school for only u children (658 -r- 60). 



In ordinary living-rooms,' in which the necessary space (800 cu. f 

 for every inmate, the air is sufficiently renewed by the numerous pores pos^ 

 by the walls of the rooms, as well as by the going in and out, and further, in win- 



