Rule 17.8.220 - AMBIENT AIR QUALITY STANDARD FOR SETTLED PARTICULATE MATTER(1) No person shall cause or contribute to concentrations of particulate matter in the ambient air such that the mass of settled particulate matter exceeds the following standard: (a) thirty-day average: 10 gm/m2, 30-day average, not to be exceeded.(2) Measurement method: For determining compliance with this rule, settled particulate matter shall be measured by the dust fall method, as more fully described in "Methods of Air Sampling and Analysis, Second Edition" (1977), Method No. 21101-0170T, or by an approved equivalent method.NEW, 1980 MAR p. 2399, Eff. 8/15/80; TRANS, from DHES, 1996 MAR p. 2285.75-2-111, 75-2-202, MCA; IMP, 75-2-202, MCA;