"Particulate matter < 1 \u00B5m (aerosol)" . . "2013-09-20" . "PM1" . . . . . "PM1" . . "valid" . "" . "Reciprocal exchange" . "PM1 - recommended unit: \u00B5g/m3" . "2013-09-20" . "" . . . . "" . . "" . .