Quick Answer
Liquid skincare is hazmat when its flash point says so, not because it is a toner or a mist. A finished product with a flash point at or below 60°C (140°F) is a Class 3 flammable liquid under 49 CFR 173.120. USPS bars it from air and international mail. Get the finished-product SDS with a measured flash point from your Korean ODM, then check the exceptions in 49 CFR 173.150 before your first parcel ships.
Picture the first restock of an alcohol-forward toner mist. Your fulfillment partner asks one question before it lists the SKU: is this hazmat? If nobody on your side can answer, the cartons sit.
The answer comes from three facts, not the product type: the flash point of the finished liquid, its alcohol content, and the size of each container. Here is where each fact comes from and how it maps to US parcel and mail rules.
On any formula with alcohol high on the ingredient list, I ask the lab for one line before anything else: the measured flash point of the finished product. Not the ethanol supplier’s sheet. The bottle’s.
Key Takeaways
- Flash point decides the class. At or below 60°C (140°F) is a flammable liquid; above 60°C and below 93°C (200°F) is a combustible liquid.
- USPS prohibits flammable liquids in air and international mail and accepts them by ground only under Limited Quantity rules.
- Two exceptions in 49 CFR 173.150 matter most for skincare: watery solutions with low alcohol, and retail cosmetics with ethyl alcohol in small containers.
- Ask your Korean ODM for an English SDS for the finished product, the flash point test method, the alcohol content and the fill size.
- Aerosols and pressurized mists follow the separate gas rules (Hazard Class 2).
What Makes Liquid Skincare Hazmat in the US?
A skincare liquid becomes a hazardous material for shipping when its flash point falls inside the Class 3 limits. A flammable liquid is a liquid with a flash point of not more than 60°C (140°F). A combustible liquid is a liquid with a flash point above 60°C (140°F) and below 93°C (200°F), as long as it meets no other hazard class (49 CFR 173.120).
Flash point is the lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near its surface. In most skincare, ethanol (often listed as alcohol denat.) is what pulls that number down. Fragrance oils and some solvents can do it too.
USPS applies these classes through Publication 52, section 343. Its bands decide where a parcel can travel.
| Finished-product flash point | Class | USPS mail rule (Pub 52, section 343) |
|---|---|---|
| 20°F (-7°C) or below | Flammable liquid | Not mailable. |
| Above 20°F (-7°C) up to 140°F (60°C) | Flammable liquid | Domestic ground only, as a Limited Quantity surface material, packed under Packaging Instruction 3A or 3B. No air, no international mail. |
| Above 140°F (60°C) up to 200°F (93°C) | Combustible liquid | Domestic ground as a Limited Quantity consumer commodity, or domestic air if it qualifies as an ID8000 material, under Packaging Instruction 3B. No international mail. |
| Above 200°F (93°C) | Not regulated as hazmat | Mailable under the general packaging rules, if no other hazard class applies. |
Packaging Instruction 3A adds the packing details. The outer box needs the DOT Limited Quantity surface mark, and each bottle needs a secure screw cap. When the flash point is 73°F (23°C) or lower, a nonmetal bottle may hold no more than 1 pint (USPS Packaging Instruction 3A).
Leak-proof packing for every liquid is covered in the parcel drop and leak test guide. This post stays on the hazmat call.
Who Asks the Hazmat Question Along Your Supply Chain
Every handoff after the filling line asks the same question, and each one relies on the SDS your Korean ODM writes. The rules differ by leg, so the same toner can pass on one route and be refused on another.
- Korean ODM. Classifies the finished product and writes the SDS. Everyone downstream copies from it.
- International leg. Air cargo from Korea follows dangerous goods rules for aircraft, covered in the air vs ocean freight guide. This post stays on US domestic parcels.
- US fulfillment. A 3PL or marketplace warehouse decides which SKUs it can store and ship, as the fulfillment comparison explains. Marketplaces also run their own hazmat review of listings, so treat it as a separate check.
- Carriers. UPS and FedEx ship under the federal Hazardous Materials Regulations in 49 CFR, and each sets its own terms for hazmat accounts. Confirm what your account allows before you print a label.
- USPS. Anything you mail follows Publication 52, which sets its own limits on top of the federal classes.
The SDS is one of the delivery documents your ODM should hand over at ship-out. The next step is reading the shipping lines inside it.
How Do You Read an SDS Before You Ship?
Start with section 9, which lists the flash point, then check sections 2 and 14. Section 9 gives you the number. Section 14 should give the UN number and transport class, but a US-format SDS can leave it blank.
The reason sits in OSHA’s rules. Appendix D to 29 CFR 1910.1200 lists flash point under section 9 and marks sections 12 through 15, including transport information, as non-mandatory. A blank section 14 is not proof that a product is unregulated.
Read the flash point line closely. A value written as “not applicable” needs the test behind it. The federal definition names closed-cup methods such as ASTM D56, ASTM D3278 and ASTM D93. For a mixture, it says to test the material in the form in which it ships. That means the finished formula, not a raw ingredient.
What to request from your Korean ODM
- An English SDS for the finished product, not the ingredient suppliers’ SDSs.
- The flash point result and the test method behind it, for example ASTM D93 closed cup.
- Alcohol content by volume for the finished formula, and the type of alcohol.
- Fill volume and container material (glass or plastic) for each SKU.
- Whether the pack is pressurized, such as an aerosol or bag-on-valve mist.
“I’m Liz, I run altameet from Manhattan, NYC. The hazmat question is cheapest to answer before the formula is locked, because the alcohol level and the bottle size are still open. If you want a quick gut-check on whether your Korean ODM brief is ready, I’ll give you 15 minutes free.”
Three Exceptions That Can Take a Formula Out of the Rules
Section 173.150 of the federal hazmat rules sets three exceptions that fit skincare: low-alcohol watery solutions, combustible liquids in non-bulk packaging, and retail cosmetics with ethyl alcohol in small containers. Each one has conditions, and each applies only when the hazmat table entry for the material points to section 173.150.
| Exception | Condition | What it means for a toner or mist |
|---|---|---|
| Aqueous alcohol solution, 173.150(e) | 24 percent or less alcohol by volume, no other hazardous material, and no less than 50 percent water | Not subject to the hazmat rules. With 24 percent or less alcohol but less water, it may be reclassed as a combustible liquid. |
| Combustible liquid, 173.150(f) | Classed as a combustible liquid, in non-bulk packaging, and not a hazardous substance, hazardous waste or marine pollutant | Not subject to the hazmat rules. A flammable liquid with a flash point at or above 38°C (100°F) can be reclassed as combustible, but not for air or vessel transport. |
| Retail products with ethyl alcohol, 173.150(g) | Cosmetics sold as retail products with not more than 70 percent ethyl alcohol by volume, in non-glass containers up to 0.47 liters or glass up to 0.23 liters, with no more than 5.6 liters of liquid per outer box | Excepted from the hazmat rules. Larger containers, up to set limits, need the company name and the words “Contains Ethyl Alcohol” on the package. By air, no inner container may exceed 0.47 liters. |
The 24, 50 and 70 percent lines and the marking limits come from 49 CFR 173.150. These are federal carrier rules. USPS sets mailability in Publication 52, which has its own packaging instruction for ethanol-based liquids (3D). Read it before you mail a product that rests on one of these exceptions.
If a toner only needs alcohol for feel or a fast dry-down, ask the lab whether a lower level keeps the formula inside the 173.150(e) exception. That conversation belongs in the brief, before stability testing starts.
What Goes Wrong When the Class Is Wrong?
A wrong class fails in two directions. Declare too little and a flammable parcel rides in a network that bans it. Declare too much and you pay for hazmat handling that the product never needed.
The first failure is the serious one. USPS prohibits flammable liquids in air and international mail outright, and federal hazmat law sets civil penalties for violations (49 U.S.C. 5123). The second failure costs margin quietly, because a hazmat flag narrows your carrier and warehouse options.
Two quieter traps catch growing brands: a reformulation that raises alcohol after the first SDS, and a new fill size that crosses a 173.150(g) container limit. Both need a fresh check.
Five Checks Before Your First Parcel Ships
Run these five checks in order for every liquid SKU, and repeat them when the formula or fill size changes. Stop at the first step that gives a clear answer.
| Step | Check | Rule | Result |
|---|---|---|---|
| 1 | Read SDS section 9 for the flash point and section 14 for transport data. | 29 CFR 1910.1200, Appendix D | No flash point listed? Ask the ODM to test the finished product. |
| 2 | Place the flash point: 60°C (140°F) or below is flammable, above 60°C and below 93°C (200°F) is combustible, above 93°C is outside the hazmat rules. | 49 CFR 173.120; Pub 52, section 343.1 | Above 93°C with no other hazard: ship as a regular liquid. |
| 3 | Is it a water-based solution with 24 percent alcohol or less, at least half water, and no other hazardous material? | 49 CFR 173.150(e) | Not subject to the federal hazmat rules. |
| 4 | Is it a retail cosmetic with 70 percent ethyl alcohol or less in a small container? | 49 CFR 173.150(g) | Check the glass and non-glass size limits and the air limit. |
| 5 | Is the pack an aerosol or a pressurized mist? | Pub 52, section 342 | Separate gas rules apply. Check them on their own. |
Keep the answers in one sheet per SKU, with the SDS date next to them. Your 3PL will ask for it, and so will every carrier you add. For channel planning, see the guide to selling Korean cosmetics in the US.
Flammable Liquid Shipping Checklist
Get the five checks above as a one-page sheet for every liquid SKU, straight to your inbox.
Frequently Asked Questions
Can an alcohol-free toner still be hazmat?
Yes. Alcohol is the usual cause, but fragrance oils and some solvents also lower the flash point. The measured flash point of the finished product decides, not the word alcohol-free on the label.
Can I mail a flammable toner to a US customer?
Only by ground. USPS bars flammable liquids from air transportation and international mail, so the parcel must travel by surface under the Limited Quantity rules, with the surface mark from Packaging Instruction 3A.
Who is responsible for the hazmat classification?
The party that offers the package for shipment, usually your brand or the 3PL shipping on your behalf. The ODM’s SDS is the evidence, so keep a dated copy with each SKU record.
Do I need a new SDS when the ODM changes the formula?
Yes, whenever the change can move the flash point or the alcohol content. A new fragrance, a higher alcohol level or a new solvent all count, so ask for an updated SDS and rerun the five checks.
By Liz Song, K-beauty sourcing consultant.
