§ 58.30 - Special considerations for data comparisons to the NAAQS.

§ 58.30 Special considerations for data comparisons to the NAAQS.

(a) Comparability of PM_2.5 data. The primary and secondary annual and 24-hour PM_2.5 NAAQS are described in part 50 of this chapter. Monitors that follow the network technical requirements specified in § 58.11 are eligible for comparison to the NAAQS subject to the additional requirements of this section. PM_2.5 measurement data from all eligible monitors are comparable to the 24-hour PM_2.5 NAAQS. PM_2.5 measurement data from all eligible monitors that are representative of area-wide air quality are comparable to the annual PM_2.5 NAAQS. Consistent with appendix D to this part, section 4.7.1, when micro- or middle-scale PM_2.5 monitoring sites collectively identify a larger region of localized high ambient PM_2.5 concentrations, such sites would be considered representative of an area-wide location and, therefore, eligible for comparison to the annual PM_2.5 NAAQS. PM_2.5 measurement data from monitors that are not representative of area-wide air quality but rather of relatively unique micro-scale, or localized hot spot, or unique middle-scale impact sites are not eligible for comparison to the annual PM_2.5 NAAQS. PM_2.5 measurement data from these monitors are eligible for comparison to the 24-hour PM_2.5 NAAQS. For example, if a micro- or middle-scale PM_2.5 monitoring site is adjacent to a unique dominating local PM_2.5 source, then the PM_2.5 measurement data from such a site would only be eligible for comparison to the 24-hour PM_2.5 NAAQS. Approval of sites that are suitable and sites that are not suitable for comparison with the annual PM_2.5 NAAQS is provided for as part of the annual monitoring network plan described in § 58.10.

(b) [Reserved]

[71 FR 61302, Oct. 17, 2006, as amended at 78 FR 3283, Jan. 15, 2013]