40 CFR § 61.121 - Definitions.

---
identifier: "/us/cfr/t40/s61.121"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 61.121 - Definitions."
title_number: 40
title_name: "Protection of Environment"
section_number: "61.121"
section_name: "Definitions."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "61"
part_name: "NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS"
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"
regulatory_source: "38 FR 8826, Apr. 6, 1973, unless otherwise noted."
cfr_part: "61"
---


# 61.121 Definitions.

(a) *Elemental phosphorus plant* or *plant* means any facility that processes phosphate rock to produce elemental phosphorus. A plant includes all buildings, structures, operations, calciners and nodulizing kilns on one contiguous site.

(b) *Calciner* or *Nodulizing kiln* means a unit in which phosphate rock is heated to high temperatures to remove organic material and/or to convert it to a nodular form. For the purpose of this subpart, calciners and nodulizing kilns are considered to be similar units.