Table 4.

Comparison of IAQ parameters on locations arranged by type and efficiency of installed filters in air treatment systems.

Substance	Week No.	High Efficiency PM-Filters a (n = 5)		Standard PM-Filters b (n = 6)		p-Value
		Median	Range	Median	Range
Acrolein	1	0.09	<0.001–0.13	0.12	<0.001–0.14	0.41
	2	0.09	<0.001–0.13	0.11	0.10–0.19	0.09
Formaldehyde	1	2.9	2.7–4.7	3.65	3.1–15.5	0.31
	2	3.5	3.4–5.2	4.05	2.2–21.7	0.42
NO2	1 + 2	16.20	4.9–17.0	16.55	13.6–19.6	0.13
TVOC	1	0.15	50.9–2418	0.34	56.2–2928	0.64
	2	0.30	33.1–2449	0.46	58.0–1142	0.61
PM-4.0	1	0.50	<0.01–2.7	3.05	1.5–4.4	<0.05
	2	0.05	<0.01–1.0	6.90	3.9–9.4	<0.01
Benz(a)pyrene	1	<0.3 × 10−6	<0.3 × 10−6	3.5 × 10−5	2.4–6.1 × 10−5	<0.01 × 10−6
	2	<0.3 × 10−6	<0.3 × 10−6	5.7 × 10−5	3.7–6.8 × 10−5	<0.01 × 10−6

^a Type H13-14 with efficicency of >99.95%; ^b Type F7-F8 with efficiency of 80–90%.