UN1791 hypochlorite solution decoder.

The UN1791 row in the Hazardous Materials Table

The table below is 49 CFR 172.101 as published in the eCFR, current through October 29, 2026, for UN1791. Columns are: class (3), packing group (5), label codes (6), special provisions (7), packaging exceptions (8A), non-bulk packaging (8B), bulk packaging (8C), quantity limits for passenger aircraft or railcar (9A) and cargo aircraft only (9B), and vessel stowage (10A and 10B). UN1791 has 2 rows, so each one is listed.

Reading the packaging columns

Columns 8A to 8C do not hold rules themselves; they point to sections of part 173. For this entry they point to:

• 173.154: Exceptions for Class 8 (corrosive materials).
• 173.202: Non-bulk packagings for liquid hazardous materials in Packing Group II.
• 173.242: Bulk packagings for certain medium hazard liquids and solids, including solids with dual hazards.
• 173.203: Non-bulk packagings for liquid hazardous materials in Packing Group III.
• 173.241: Bulk packagings for certain low hazard liquid and solid materials.

Exceptions in column 8A apply only if that section is referenced for the specific material in the table, so a limited quantity route that exists for one UN number is not automatically open to another.

Special provisions on this entry

The letter prefixes on special provisions tell you where each applies (172.102(c)): a code of only numbers is multi-modal; "A" applies only to transportation by aircraft; "B" only to bulk packaging; "IB" and "IP" only to IBCs; "N" only to non-bulk packaging; "T" and "TP" only to UN portable tanks.

• 148: The text of provision 148 in 172.102, as read, concerns domestic transport of blasting-agent materials by cargo tank motor vehicles under 173.66; it does not mention hypochlorite, so treat its appearance on this entry as something to confirm with PHMSA.
• A7: Steel packagings must be corrosion-resistant or have protection against corrosion.
• B2: MC 300, 301, 302, 303, 305 and 306 and DOT 406 cargo tanks are not authorized.
• B15: Packagings must be protected with non-metallic linings impervious to the lading or have a suitable corrosion allowance.
• IB2: Authorized IBCs: metal (31A, 31B, 31N), rigid plastic (31H1, 31H2) and composite (31HZ1).
• IP5: IBCs must have a device to allow venting, with its inlet in the vapor space under maximum filling conditions.
• N34: Aluminum construction materials are not authorized for any part of a packaging normally in contact with the hazardous material.
• T7: a portable tank instruction. It set the minimum test pressure, shell thickness, bottom opening and pressure relief requirements for UN portable tanks.
• TP2: Portable tank maximum degree of filling set by the formula in the provision (paragraph a).
• TP24: The portable tank may be fitted with a device to prevent build-up of excess pressure from slow decomposition, located in the vapor space and preventing unacceptable leakage on overturning.
• 386: When transported by private motor carrier only, certain corrosive liquids may be packed in polyethylene bottles no larger than 3.785 L (one gallon) inside an open-top heavy-wall high density polyethylene box, under the conditions in the provision.
• IB3: Authorized IBCs: metal (31A, 31B, 31N), rigid plastic (31H1, 31H2) and composite (31HZ1 and 31HA2, 31HB2, 31HN2, 31HD2, 31HH2).
• T4: a portable tank instruction. It set the minimum test pressure, shell thickness, bottom opening and pressure relief requirements for UN portable tanks.

The two packing groups are two different rows

Hypochlorite solutions are listed once in the table with a Packing Group II row and a Packing Group III row, and the rows differ on almost every column. Group II carries special provisions 148, A7, B2, B15, IB2, IP5, N34, T7, TP2 and TP24, non-bulk packaging in 173.202 and bulk packaging in 173.242. Group III carries 386, IB3, N34, T4, TP2 and TP24, with 173.203 and 173.241. The shipper has to know which group the product is classed in before choosing a package, because the rows differ on almost every column.

Materials to keep out of the packaging

Several special provisions are materials rules rather than paperwork rules, and the letter prefix says where each applies (172.102(c)). N34 is an N code, so it applies to non-bulk packaging: aluminum construction materials are not authorized for any part of a packaging normally in contact with the hazardous material. B15 is a B code, a bulk packaging rule: packagings must be protected with non-metallic linings impervious to the lading or have a suitable corrosion allowance. B2, also bulk, excludes MC 300, 301, 302, 303, 305 and 306 and DOT 406 cargo tanks for Packing Group II. A7 is an A code, so it applies only to transportation by aircraft: steel packagings must be corrosion-resistant or protected against corrosion.

IP5 requires IBCs to have a venting device whose inlet sits in the vapor space under maximum filling, and TP24 allows the portable tank to carry a device preventing build-up of excess pressure from slow decomposition. Both reflect that hypochlorite solutions can generate gas in the container.

Special provision 148 on the Packing Group II row

The Packing Group II row lists special provision 148. The text of 148 in 172.102 as read on November 2, 2026 says that for domestic transportation the entry directs to 173.66 for standards on transporting bulk hazardous material for blasting by cargo tank motor vehicles. That does not obviously relate to hypochlorite, so this page reports the table as published and flags the point for review rather than interpreting it. Shippers who see 148 on their paperwork should confirm its meaning with the PHMSA Hazardous Materials Information Center.

Limited quantities and vessel stowage

Section 173.154 lets limited quantities of Class 8 Packing Group II and III be excepted from labeling and from specification packaging when packed in combination packagings with inner packagings of not over 1.0 L (Packing Group II) or 5.0 L (Packing Group III) for liquids, in a package of not over 30 kg (66 pounds) gross weight. Limited quantity shipments are not subject to the placarding subpart. For vessels, column 10B shows stowage code 26, "Stow away from acids", and Packing Group III adds 53 (separated from alkaline compounds) and 58 (separated from cyanides).

ERG 2024 Guide 154: Substances - Toxic and/or Corrosive (Non-Combustible)

The ERG 2024 numerical index lists UN1791 against Guide 154. The guide appears on pages 237 to 238 of the 2024 guidebook. The guidebook is meant for first responders during the initial phase of an incident, and it says to call 911 and then the emergency response telephone number on the shipping paper.

• Health first: "TOXIC and/or CORROSIVE; inhalation, ingestion or skin contact with material may cause severe injury or death", and the guide says to avoid any skin contact.
• Fire or explosion: the substance itself does not burn but may decompose on heating to give corrosive or toxic fumes; some are oxidizers that may ignite combustibles such as wood, paper, oil and clothing; corrosives in contact with metals may evolve flammable hydrogen gas.
• Evacuation: isolate a spill or leak area for at least 50 meters (150 feet) for liquids and 25 meters (75 feet) for solids in all directions; for a tank, rail tank car or highway tank in a fire, isolate for 800 meters (1/2 mile).
• Response: small fire, dry chemical, CO2 or water spray; do not get water inside containers; absorb or cover a spill with dry earth, sand or other non-combustible material.

The guide is a starting point until the material is identified. Read the full guide in the current ERG, and use the shipping paper emergency number for product-specific advice.

Placards, quantity and vessel stowage

8 is a Table 2 category in 172.504(e), so the placard is CORROSIVE. On a highway vehicle with less than 454 kg (1,001 pounds) aggregate gross weight of Table 2 materials in non-bulk packages, no placard is required, but bulk packagings and materials subject to 172.505 are not eligible for that exception (172.504(c)).

Vessel stowage is the category in column 10A (B), which the table sets for this entry, plus the column 10B codes. Hazmat shipped as a limited quantity is allocated stowage category A and is not subject to the column 10B stowage codes (176.63(a)).

• 26: Stow "away from" acids.
• 53: Stow "separated from" alkaline compounds.
• 58: Stow "separated from" cyanides.

Worked example

A pool supply distributor ships a Packing Group III hypochlorite solution in 4 L jugs, four to a case. Each case holds 16 L net. By passenger aircraft the net limit per package is 5 L, so 16 L is over the limit; by cargo aircraft the limit is 60 L, so it is within. By highway with 600 pounds gross of Class 8 on the truck and no bulk packaging, the vehicle is under the 1,001 pound threshold in 172.504(c), so no CORROSIVE placard is required, although the package marks and shipping papers rules still apply unless the limited quantity exceptions are used.

Limits

This page reads the 172.101 table, the 172.102 special provisions, 172.504 and the section titles named above, plus ERG 2024. It does not classify your material, choose a proper shipping name, or build shipping papers, marks, labels or training requirements. The checker compares your net quantity to the printed column 9A and 9B limits and applies the 1,001 pound rule to the class on the row; it does not model subsidiary hazard placards (172.505), mixed loads, state rules or carrier restrictions. Special provisions are shown in summary; read the full text in 172.102 before relying on one. Hazmat shipping needs trained hazmat employees (49 CFR part 172, subpart H).

Sources

Sources opened and read November 2, 2026.

• eCFR: 49 CFR 172.101, Hazardous Materials Table (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 172.102, special provisions (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 172.504, general placarding requirements (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 173.154, Exceptions for Class 8 (corrosive materials) (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 173.202, Non-bulk packagings for liquid hazardous materials in Packing Group II (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 173.242, Bulk packagings for certain medium hazard liquids and solids, including solids with dual hazards (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 173.203, Non-bulk packagings for liquid hazardous materials in Packing Group III (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 173.241, Bulk packagings for certain low hazard liquid and solid materials (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 176.84, other requirements for stowage, cargo handling and segregation (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR 176.63, stowage locations (current through October 29, 2026) (read November 2, 2026)
• PHMSA: Emergency Response Guidebook (ERG) landing page (read November 2, 2026)
• PHMSA: ERG 2024 PDF, numerical index and guide pages (the phmsa.dot.gov host refused automated requests; the Internet Archive copy of this file was read) (read November 2, 2026)