2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



the air temperature, relative humidity, and air movement to remain 

 normal but let the surrounding walls be raised to a temperature of 

 32° C. Radiation loss from a human subject would now be negligible, 

 the normal balance between heat produced and heat lost would be 

 destroyed, and until readjustment is made, a condition of discomfort 

 results. In actual schoolroom conditions, a student near an unshielded 

 steam radiator or other artificial heat source is exposed to a tempera- 

 ture much higher than his surface temperature. In classes, the student 

 is surrounded by other students and the summation of the solid angles 

 subtended at a point on one student by the other students may be 

 very appreciable. 



As a rough example, assume a class of students placed in rows, 

 with spaces of 2 feet between students in a row, and the same dis- 

 tance between rows. To simplify matters, imagine each student to 

 be cylindrical, i foot in diameter and 4 feet high. The four students 

 nearest to a given student would occupy roughly 10 per cent of the 

 total space to which the central student is radiating. The four next 

 nearest students exposed to the given student would occupy an addi- 

 tional 5 per cent, and the eight next nearest another 4 per cent. Sum- 

 ming up, the amount of space occupied by surrounding students would 

 be about 20 per cent of the total space to which the central students 

 radiate. If we reduce the space between students to only i foot 

 instead of 2 and proceed to sum up in a similar manner, the area 

 occupied by the other students increases to about 35 per cent of the 

 whole. For a spacing of 3 feet between students it reduces to only 

 10 per cent. In other words, when students are spaced i foot apart, 

 the total radiation loss of each student is some 35 per cent less than 

 if he were alone in the room. When the spacing is 2 feet between 

 students the radiation loss is 20 per cent less than if he were alone, 

 and when the spacing is 3 feet the radiation loss is 10 per cent less. 

 These rough figures serve in a general way to show" the relationship 

 between the spacing of students and the radiation loss of individual 

 students. 



For a given wall temperature, what air conditions produce maxi- 

 mum comfort? Evidently if the walls are cold an increased air tem- 

 perature is indicated, and vice versa. A further study of the efifect on 

 a subject of various wall temperatures under controlled air conditions 

 is needed. Such a study should tell us to what extent one's radiation 

 loss may be altered without producing discomfort and should furnish 

 evidence as to the minimum spacing advisable in classrooms without 

 injurious reaction resulting from decreased heat loss. 



