Hazmat is not one rule but nine hazard classes, each with its own answer, and the slice that a consumer can actually ship is small. Postal rules define hazardous materials as articles or substances the Department of Transportation designates as capable of posing unreasonable risks to health, safety or property during transportation, then set mailability class by class. Almost everything a household ships that qualifies at all moves as a limited quantity surface material, which means ground services and nothing faster.
The first question is never how to pack it. The first question is which class the contents fall into.
The definition is broad, the treatment is specific, and the pattern across the nine classes is easier to see side by side than in prose.
| Class | Covers | By air | By surface |
|---|---|---|---|
| 1 Explosives | Fireworks, ammunition, primers, powder, fuses | Prohibited | Generally prohibited, with narrow approved exceptions for toy propellant devices and safety fuses |
| 2 Gases | Aerosols, butane, compressed and toxic gases | Flammable and toxic gases prohibited; nonflammable gases only as air-eligible consumer commodities | Toxic gases prohibited; flammable and nonflammable gases permitted as limited quantity surface materials |
| 3 Flammable liquids | Fragrance, polish, solvents, fuels | Flammable liquids prohibited | Flashpoint of 20 degrees F or below prohibited; the rest as limited quantity surface materials |
| 4 Flammable solids | Matches, metallic sodium, nitrocellulose | Prohibited | Permitted where they qualify as limited quantity surface materials; safety matches by surface only |
| 5 Oxidizers and organic peroxides | Hydrogen peroxide solutions, pool chemicals | Permitted only as qualifying limited quantity air materials | Permitted as qualifying limited quantity surface materials |
| 6 Toxic and infectious substances | Poisons, irritants, diagnostic specimens | Toxic substances only as limited quantity consumer commodities | Same limited quantity route, with authorized-party rules for certain poisons |
| 7 Radioactive materials | Instruments and sources bearing radioactive labels | Prohibited | Prohibited where a White-I, Yellow-II, Yellow-III or Fissile label is required; low-activity exceptions have their own UN numbers |
| 8 Corrosives | Acids, alkalis, wet-cell batteries | Only as qualifying limited quantity air materials | Liquid mixtures of 1 pint or less at 15 percent or less corrosive content; solids 10 lb or less at 10 percent or less |
| 9 Miscellaneous | Lithium batteries, dry ice, magnets, air bags, asbestos | Only air-eligible consumer commodity material qualifies | Only lithium batteries, dry ice, magnetized material and qualifying consumer commodities are mailable at all |
Read down the air column and the shape of the whole subject appears: aircraft are where hazmat rules bite hardest, because pressure changes and a sealed hold turn a small leak into a serious event. Trucks tolerate what planes cannot, which is why so many consumer goods end up ground-only rather than banned.
Nearly every hazmat shipment a small seller can legally make travels under this heading, so it is worth understanding before anything is packed.
Publication 52 section 336 describes limited quantity surface material as covering goods whose form, quantity and packaging keep the hazard small, and says in as many words that the category absorbed everything once designated ORM-D. Our marking reference quotes that sentence in full alongside the federal rule that retired the old designation.
The same section adds two constraints people trip over. Limited quantity surface materials are prohibited in Priority Mail Express and Priority Mail, and putting surface markings on either product to dodge air transport is itself against the rules. The material generally has to qualify as a consumer commodity as well, meaning it is packaged and sold in a form intended for personal or household use.
Section 332 sets the entry test: a material qualifies for the limited quantity provision only when the hazardous materials table shows an exception for it, and the mailer carries the burden of knowing the correct hazard class before mailing. Publication 52 points shippers to the postal Pricing and Classification Service Center when the answer is not obvious, and that is the right address for an unusual product rather than a forum.
We run a dangerous goods model at quote time rather than at the counter, so the answer arrives before you pay rather than after.
| Carrier | Service | Price | Transit window returned |
|---|---|---|---|
| UPS | Ground Saver | $16.47 | Not returned for this row |
| USPS | Ground Advantage | $16.97 | 7-8 business days |
| UPS | Ground | $17.00 | 6-7 business days |
| FedEx | Ground Economy | $17.52 | 6-7 business days |
| UPS | 2nd Day Air | $28.29 | 2-3 business days |
Publication 52 defines it as hazardous material packaged and distributed in a quantity and form suitable for retail sale and personal or household use. A retail can of hairspray fits. The same chemistry in a five gallon drum does not, whatever the label says.
Postal text is explicit that knowing the correct hazard class before mailing is the shipper responsibility, not the counter clerk. That is worth remembering before describing a product loosely and hoping the system sorts it out.
Across the hazmat chapters the same instruction repeats: labels and text markings belong on the address side of the mailpiece. A mark on the bottom of a carton is a mark nobody handling the parcel will see.
Anything the Department of Transportation designates as capable of posing unreasonable risks to health, safety or property in transport. That includes aerosols, flammable liquids, lithium batteries, magnets, dry ice, corrosives and explosives, spread across nine hazard classes.
Rarely. Explosives, flammable solids, radioactive materials, flammable gases and flammable liquids are all prohibited from air transportation in the mail, and the exceptions that do fly must qualify as air-eligible consumer commodity material.
Limited quantity surface materials. That postal category absorbed the old designation and carries a restriction of its own, since goods in it cannot travel by Priority Mail Express or Priority Mail.
Only for the consumer limited quantity items our model recognizes, such as fragrance and retail aerosols, and only on ground services with an acknowledgement at review. Fuels, pesticides, corrosives, explosives and damaged batteries are declined.