Table 3.

Variations in the PM when outside was heavy pollution (μg/m³).

	Outside		Closed system		Screen door system		Open system
	PM2.5	PM10	PM2.5	PM10	PM2.5	PM10	PM2.5	PM10
Before train entered	549	573	544	539	438	446	328	359
After train left			535	524	444	448	337	366
Percentage increase			−1.7%	−2.8%	1.4%	0.4%	2.7%	1.9%