# Substances requiring stabilization (otherwise forbidden) — Postal shipping restrictions by item category

For Substances requiring stabilization (otherwise forbidden), carrier is US DOT (49 CFR, all modes); restriction type is restricted; scope is transportation in commerce (US); conditions is The qualifying word 'stabilized' may be added to the proper shipping name where without stabilization the substance would be forbidden for transportation according to 49 CFR 173.21(f), recorded from its source on 2026-08-10.

- **Item category:** Substances requiring stabilization (otherwise forbidden) _(verified: appears in the quote below)_
- **Carrier:** US DOT (49 CFR, all modes) _(our reading, not quoted from the source)_
- **Restriction type:** restricted _(our reading, not quoted from the source)_
- **Scope:** transportation in commerce (US) _(our reading, not quoted from the source)_
- **Conditions:** The qualifying word 'stabilized' may be added to the proper shipping name where without stabilization the substance would be forbidden for transportation according to 49 CFR 173.21(f). _(verified: appears in the quote below)_

## What the source says

> stabilized ” may be added in association with the proper shipping name , as appropriate, where without stabilization the substance would be forbidden for transportation according to

## Source

- https://www.law.cornell.edu/cfr/text/49/172.101

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/).