---
kind: "unit"
title: "40"
title_heading: "Protection of Environment"
key: "chI/subchC/part53"
level: "part"
label: "Part 53"
heading: "Ambient Air Monitoring Reference and Equivalent Methods"
release: "ecfr-current"
date: "2026-08-27"
url: "https://uscodex.org/cfr/40/chI-subchC-part53"
sections_count: 47
---

# Part 53 — Ambient Air Monitoring Reference and Equivalent Methods

Title 40 C.F.R. — Protection of Environment › Chapter I — Environmental Protection Agency › Subchapter C — Air Programs

## Contents

- [Subpart A — General Provisions](/cfr/40/chI-subchC-part53-subpartA.md)
- [Subpart B — Procedures for Testing Performance Characteristics of Automated Methods for SO 2 , CO, O 3 , and NO 2](/cfr/40/chI-subchC-part53-subpartB.md)
- [Subpart C — Procedures for Determining Comparability Between Candidate Methods and Reference Methods](/cfr/40/chI-subchC-part53-subpartC.md)
- [Subpart D — Procedures for Testing Performance Characteristics of Methods for PM 10](/cfr/40/chI-subchC-part53-subpartD.md)
- [Subpart E — Procedures for Testing Physical (Design) and Performance Characteristics of Reference Methods and Class I and Class II Equivalent Methods for PM 2.5 or PM 10-2.5](/cfr/40/chI-subchC-part53-subpartE.md)
- [Subpart F — Procedures for Testing Performance Characteristics of Class II Equivalent Methods for PM 2.5](/cfr/40/chI-subchC-part53-subpartF.md)