---
type: restriction
id: usps-flammable-solids-hazard-class-4-domestic-air
asset: shipping-restrictions-by-class
title: "Flammable solids (Hazard Class 4) — domestic air — Postal shipping restrictions by item category"
sources:
  - https://pe.usps.com/text/pub52/pub52c3_023.htm
source_quote: "Domestic Mail via Air Transportation: All flammable solids are prohibited."
generated: true
harvested: 2026-08-04
stale_after: 2027-08-04
item_category: "Flammable solids (Hazard Class 4) — domestic air"
carrier: "USPS"
restriction_type: "prohibited"
scope: "domestic mail via air transportation"
conditions: "All flammable solids are prohibited from domestic air mail"
verified: false
unverified_fields: carrier, item_category
---
**Item category:** Flammable solids (Hazard Class 4) — domestic air

**Carrier:** USPS

**Restriction type:** prohibited

**Scope:** domestic mail via air transportation

**Conditions:** All flammable solids are prohibited from domestic air mail

> Domestic Mail via Air Transportation: All flammable solids are prohibited.

Source: <https://pe.usps.com/text/pub52/pub52c3_023.htm>