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

---
identifier: "/us/cfr/t40/s58.30"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 58.30 - Special considerations for data comparisons to the NAAQS."
title_number: 40
title_name: "Protection of Environment"
section_number: "58.30"
section_name: "Special considerations for data comparisons to the NAAQS."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "58"
part_name: "AMBIENT AIR QUALITY SURVEILLANCE"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7403, 7405, 7410, 7414, 7601, 7611, 7614, and 7619."
regulatory_source: "44 FR 27571, May 10, 1979; 59 FR 41628, Aug. 12, 1994, unless otherwise noted."
cfr_part: "58"
---


# 58.30 Special considerations for data comparisons to the NAAQS.

(a) *Comparability of* PM <sub>2.5</sub> *data.* The primary and secondary annual and 24-hour PM <sub>2.5</sub> 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 <sub>2.5</sub> measurement data from all eligible monitors are comparable to the 24-hour PM <sub>2.5</sub> NAAQS. PM <sub>2.5</sub> measurement data from all eligible monitors that are representative of area-wide air quality are comparable to the annual PM <sub>2.5</sub> NAAQS. Consistent with appendix D to this part, section 4.7.1, when micro- or middle-scale PM <sub>2.5</sub> monitoring sites collectively identify a larger region of localized high ambient PM <sub>2.5</sub> concentrations, such sites would be considered representative of an area-wide location and, therefore, eligible for comparison to the annual PM <sub>2.5</sub> NAAQS. PM <sub>2.5</sub> 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 <sub>2.5</sub> NAAQS. PM <sub>2.5</sub> measurement data from these monitors are eligible for comparison to the 24-hour PM <sub>2.5</sub> NAAQS. For example, if a micro- or middle-scale PM <sub>2.5</sub> monitoring site is adjacent to a unique dominating local PM <sub>2.5</sub> source, then the PM <sub>2.5</sub> measurement data from such a site would only be eligible for comparison to the 24-hour PM <sub>2.5</sub> NAAQS. Approval of sites that are suitable and sites that are not suitable for comparison with the annual PM <sub>2.5</sub> 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]