THE INFLUENCE OF PLANTS ON THE AIR IN HOUSES 
George B. Rigg, Thomas G. Thompson, and William L. Gilliland 
(Received for publication October 30, 1922) 
The Problem 
The experimental work reported in this paper deals with the percentage 
of carbon dioxide in the air of a city greenhouse at various times of day. 
The discussion deals with the relation between the presence of plants in 
rooms at night and the comfort and safety of persons occupying the rooms. 
It has been known 1 for several years that ventilation of occupied rooms 
is necessary to keep down the temperature, secure cooling movements of the 
air, and maintain a low humidity, and not to let out air containing a high 
percentage of carbon-dioxide and admit that having a low carbon-dioxide 
content. It is possible also that one good effect of ventilation is the removal 
of injurious organic matter 2 , and it is certain that it is beneficial in preventing 
the continued multiplication of pathogenic organisms. 3 
In the light of this information, it seems strange that so little attention 
has been paid to the nature of any effects that the presence of plants may 
have on the air of rooms occupied for sleeping purposes. There is a wide¬ 
spread popular belief that plants in a room at night are injurious to persons 
sleeping in the room. The recent experience of one of us in a large hospital 
where an attendant is kept busy for several hours every day removing 
plants from the rooms at night and replacing them in the morning has 
directed attention especially to this belief. 
While most textbooks on botany and physiology simply ignore the 
subject of the relation between plants and people in sleeping rooms, a 
widely used school chart bearing the statement that it has been revised 
by the dean of the college of agriculture in a tax-supported university says: 
We can understand why plants should have no place in sleeping rooms at night for 
when light is withdrawn, the absorption of carbon dioxide stops and the plants give off 
this poisonous gas. 
Since Winslow 4 has found that air contaminated by the breathing 
of human beings until it contained an average of 20 to 60 parts of carbon- 
dioxide per ten thousand parts of air, five to fifteen times the normal amount, 
1 Winslow. Sci., n. ser., 41: 625-632. 1915. 
2 Since the above was written the writers have seen the Report of the New York State 
Commission on Ventilation (Dutton and Co., New York, 1923) which states (p.8) that 
the weight of scientific evidence is against the existence of organic poisons in respired air. 
3 Cf. Nolte. Ann. Mo. Bot. Gard. 1: 47-80. 1914. 
4 Loc. tit; also Rept. N. Y. State Com. on Ventilation cited above. 
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