---
kind: "section"
citation: "40 C.F.R. § 87.23"
title: "40"
number: "87.23"
heading: "Exhaust emission standards for Tier 6 and Tier 8 engines."
url: "https://uscodex.org/cfr/40/87.23"
---

# §87.23. Exhaust emission standards for Tier 6 and Tier 8 engines.


Exhaust emission standards apply to new aircraft engines as follows:

- (a) New turboprop aircraft engine standards apply as described in [40 CFR 1031.40](/cfr/40/1031.40.md).
- (b) New supersonic engine standards apply as described in [40 CFR 1031.90](/cfr/40/1031.90.md).
- (c) **New subsonic turbofan or turbojet aircraft engine standards apply as follows—**
  - (1) Standards for engines with rated output at or below 26.7 kN thrust apply as described in [40 CFR 1031.50](/cfr/40/1031.50.md).
  - (2) Standards for engines with rated output above 26.7 kN thrust apply as described in [40 CFR 1031.60](/cfr/40/1031.60.md).
- (d) NOX standards apply based on the schedule for new type and in-production aircraft engines as described in [40 CFR 1031.60](/cfr/40/1031.60.md).

## Notes

### Authority

Authority: 42 U.S.C. 7401 et seq.

### Source

Source: 87 FR 72350, Nov. 23, 2022, unless otherwise noted.