# Acetaldehyde ammonia — Postal shipping restrictions by item category

For Acetaldehyde ammonia, carrier is USPS; restriction type is restricted; scope is domestic mail: surface only (air prohibited); conditions is Hazard class 9, UN1841, packing group III; domestic mail air: Prohibited; domestic mail surface: 9C, recorded from its source on 2026-08-10.

- **Item category:** Acetaldehyde ammonia _(verified: appears in the quote below)_
- **Carrier:** USPS _(our reading, not quoted from the source)_
- **Restriction type:** restricted _(our reading, not quoted from the source)_
- **Scope:** domestic mail: surface only (air prohibited) _(our reading, not quoted from the source)_
- **Conditions:** Hazard class 9, UN1841, packing group III; domestic mail air: Prohibited; domestic mail surface: 9C _(verified: appears in the quote below)_

## What the source says

> Acetaldehyde ammonia 9 UN1841 III Prohibited 9C

## Source

- https://pe.usps.com/cpim/ftp/pubs/pub52/pub52.pdf

Last verified: 2026-08-10. Review by: 2027-08-10.
Part of [Postal shipping restrictions by item category](https://referencesource.org/shipping-restrictions-by-class/).