UN2794 batteries, wet, filled with acid table entry.

Where UN2794 sits in the table

This is the entry for electric storage batteries filled with acid. The row has a single special provision, A51, and the same packaging section, 159, in all three of columns 8A, 8B and 8C, meaning 173.159 governs. There is no packing group in column 5.

The wording of A51 is the notable part: "For aircraft batteries, irrespective of the quantity limitations specified in Column (9A) of the 172.101 Table or 175.75(c), wet cell batteries, UN2794 or UN2795, up to a limit of 100 kg net mass per package may be transported aboard passenger aircraft. Transport in accordance with this special provision must be noted on the shipping paper." So 30 kg in column 9A is not the only number: A51 allows 100 kg for aircraft batteries.

The full row from the eCFR copy of the table, current through October 29, 2026 and read November 2, 2026, is below. Every value is copied from 49 CFR 172.101; the last column is the regulation's own explanation of the column.

The 172.101 row, column by column

How the regulation defines the hazard class

173.136(a) says, abridged: ""corrosive material" (Class 8) means a liquid or solid that causes irreversible damage to human skin at the site of contact within a specified period of time. A liquid, or a solid which may become liquid during transportation, that has a severe corrosion rate on steel or aluminum based on the criteria in 173.137(c)(2) is also a corrosive material."

Special provisions on this entry, in the rule's words

Column 7 does not explain itself; each code is defined in 172.102. These are the definitions as printed in the eCFR text for the code listed on the row. Where a provision ends with a list of conditions that this page does not reproduce, it says so.

• A51: For aircraft batteries, irrespective of the quantity limitations specified in Column (9A) of the § 172.101 Table or § 175.75(c), wet cell batteries, UN2794 or UN2795, up to a limit of 100 kg net mass per package may be transported aboard passenger aircraft. Transport in accordance with this special provision must be noted on the shipping paper.

What else to know about this entry

173.159(a) says electric storage batteries containing electrolyte acid or alkaline corrosive battery fluid (wet batteries) may not be packed with other materials except as provided in paragraphs (g) and (h) and in 173.220 and 173.222, and that any battery or battery-powered device must be prepared and packaged to prevent a dangerous evolution of heat, short circuits and damage to terminals.

For aircraft, 173.159(b) requires the packaging to incorporate an acid- or alkali-proof liner or include a supplementary packaging with sufficient strength and adequate seals to prevent leakage of electrolyte fluid, and requires battery-powered devices to be packaged to prevent unintentional activation. 173.159(c) lists the authorized specification packagings for batteries packed without other materials, beginning with 4C1, 4C2, 4D and 4F wooden boxes, 4G fiberboard boxes, and 1D plywood, 1G fiber and 1H2 plastic drums.

Column 10B shows 53, 58 and 146. In 176.84, 53 and 58 say stow separated from alkaline compounds and cyanides, and 146 says "Category B stowage applies for unit loads in open cargo transport units."

Air quantity limits and a worked example

Columns 9A and 9B give the largest net quantity allowed in one package: column 9A for passenger-carrying aircraft or passenger-carrying rail car, column 9B for cargo aircraft only. 172.101(j) says "Forbidden" means the material may not be offered for transportation or transported in the applicable mode, and that the limit is net unless stated otherwise. For UN2794 the row shows 30 kg in column 9A and 400 kg in column 9B.

Worked example, 45 kg net in one package. Passenger aircraft or rail car (column 9A, 30 kg): over 30 kg. Cargo aircraft only (column 9B, 400 kg): within 400 kg. The calculator above applies the same comparison to the quantity you type.

Highway placard check

Class 8 is on Table 2 of 172.504(e) as CORROSIVE.

For Table 2 materials moved by highway or rail, 172.504(c) says placards are not required on a transport vehicle or freight container that contains less than 454 kg (1,001 pounds) aggregate gross weight of hazardous materials covered by Table 2, except for bulk packagings and hazardous materials subject to 172.505. In the calculator, 1,000 pounds of non-bulk Table 2 material returns "not required" and 1,001 pounds returns "required", and any bulk packaging returns "required". The weight is the aggregate gross weight of all Table 2 materials on the vehicle, not just this one UN number.

Vessel stowage and the ERG guide

Column 10A gives category A (the material may be stowed "on deck" or "under deck" on a cargo vessel or on a passenger vessel). Column 10B lists 53, 58, 146. Code 53 in 176.84: Stow "separated from" alkaline compounds. Code 58 in 176.84: Stow "separated from" cyanides. Code 146 in 176.84: Category B stowage applies for unit loads in open cargo transport units. These apply to shipments by vessel and have no effect on a truck-only move.

The Emergency Response Guidebook 2024 numerical index lists UN2794 under Guide 154, titled "Substances - Toxic and/or Corrosive (Non-Combustible)". 172.101 itself does not list ERG guide numbers; the guide number comes from the PHMSA guidebook. The guide is for first responders during the initial phase of an incident and is not a shipping-paper or compliance document.

What this page does not do

It reproduces the table row and the regulation text it points to, and applies the air-limit and 1,001 pound placard comparisons to numbers you enter. It does not classify a product, pick a packing group, decide which table row applies to your shipment, or replace the packaging sections the row points to (the 173 sections in columns 8A to 8C), the marking, labelling and shipping paper rules in part 172, or hazmat training. Hazardous materials employees must be trained; that decision and the shipping description belong to a trained person. The eCFR header for 172.101 links an amendment published at 91 FR 49310 (August 4, 2026); confirm that the version you rely on includes the latest changes. In an emergency call 911 and the emergency response telephone number on the shipping paper.

Sources

Sources opened and read November 2, 2026. Regulation text was read from the eCFR API, which publishes the current Code of Federal Regulations.

• 49 CFR 172.101, Hazardous Materials Table (eCFR text current through October 29, 2026; read November 2, 2026)
• 49 CFR 172.102, Special provisions (read November 2, 2026)
• 49 CFR 172.504, General placarding requirements (read November 2, 2026)
• 49 CFR 173.136, hazard class definitions (read November 2, 2026)
• 49 CFR 176.84, Other requirements for stowage, cargo handling, and segregation (read November 2, 2026)
• 49 CFR 173.159, Batteries, wet (read November 2, 2026)
• PHMSA: Emergency Response Guidebook 2024 English PDF, numerical index (read via the Internet Archive capture of October 31, 2026; read November 2, 2026)