40 CFR § 97.181 - General.

---
identifier: "/us/cfr/t40/s97.181"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 97.181 - General."
title_number: 40
title_name: "Protection of Environment"
section_number: "97.181"
section_name: "General."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "97"
part_name: "FEDERAL NOX BUDGET TRADING PROGRAM, CAIR NOX AND SO2 TRADING PROGRAMS, CSAPR NOX AND SO2 TRADING PROGRAMS, AND TEXAS SO2 TRADING PROGRAM"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401, 7403, 7410, 7426, 7491, 7601, and 7651,"
regulatory_source: "65 FR 2727, Jan. 18, 2000, unless otherwise noted. 71 FR 25396, 25422, and 25443, Apr. 28, 2006"
cfr_part: "97"
---


# 97.181 General.

(a) Except as otherwise provided in §§ 97.101 through 97.104, §§ 97.106 through 97.108, and subparts BB and CC and subparts FF through HH of this part, a CAIR NO<sub>X</sub> opt-in unit shall be treated as a CAIR NO<sub>X</sub> unit for purposes of applying such sections and subparts of this part.

(b) Solely for purposes of applying, as provided in this subpart, the requirements of subpart HH of this part to a unit for which a CAIR opt-in permit application is submitted and not withdrawn and a CAIR opt-in permit is not yet issued or denied under this subpart, such unit shall be treated as a CAIR NO<sub>X</sub> unit before issuance of a CAIR opt-in permit for such unit.