Table 3.

Changes of chemical substance concentration in indoor air according to indoor plant placement (μg/m³)

Indoor plant placement	Measurement time	Formaldehyde	p-value	Benzene	p-value	Toluene	p-value	Ethylbenzene	p-value	Xylene	p-value
Continuation	April	24.2	0.03	6.35	0.001	79.05	0.01	3.56	0.01	13.43	0.01
	July	21.2		2.24		62.02		1.56		2.52
	October	15.5		1.61		19.27		0.27		0.20
Withdrawal	April	29.7	0.01	6.14	NS	90.26	0.05	3.62	NS	13.50	NS
	July	20.8		2.03		59.28		2.49		1.15
	October	13.6		9.76		43.64		3.91		20.80

Continuation, indoor plant placement during the entire season (April to September); Withdrawal, placement of indoor plants during the former observation term (April to June) and withdrawal during the latter observation term (July to September).

The p-values were calculated by Mann-Whitney test.

NS, non-significance.