40 CFR § 87.21 - Exhaust emission standards for Tier 4 and earlier engines.

---
identifier: "/us/cfr/t40/s87.21"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 87.21 - Exhaust emission standards for Tier 4 and earlier engines."
title_number: 40
title_name: "Protection of Environment"
section_number: "87.21"
section_name: "Exhaust emission standards for Tier 4 and earlier engines."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "87"
part_name: "CONTROL OF AIR POLLUTION FROM AIRCRAFT AND AIRCRAFT ENGINES"
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. 7401"
regulatory_source: "87 FR 72350, Nov. 23, 2022, unless otherwise noted."
cfr_part: "87"
---


# 87.21 Exhaust emission standards for Tier 4 and earlier engines.

Exhaust emission standards apply to new aircraft engines as described in 40 CFR 1031.40 through 1031.90.