29 CFR 1910.1200 · 49 CFR 173.120

Flammable liquid classifier by flash point

One flash point, three labels, before the SDS goes out.

Enter the closed cup flash point and initial boiling point from SDS Section 9 to get the OSHA/GHS category, the DOT packing group and the NFPA 30 class side by side.

Last updated 2026-09-28. Math runs in your browser, no data leaves your computer.

Take both numbers from SDS Section 9 or the test report. The three rule sets draw their lines at slightly different temperatures, so a liquid close to a boundary can land in different bands on the SDS, the shipping paper and the storage plan.

Units

Use a closed cup result, because 49 CFR 173.120(c) and NFPA 30 both classify on closed cup figures and an open cup number usually reads higher.

Enter the initial boiling point, not the end of the range, since it decides category 1 against 2 and packing group I against II.

Before the booking, screen the name on the invoice. Shipment pre-check is on the paid plans, from USD 59 a month.

General guidance only. Verify against the cited primary sources before you commit to a shipment, declaration, or contract.

Where the three sets of cut points come from

The OSHA and GHS category comes from Table B.6.1 in 29 CFR 1910.1200 Appendix B, which is repeated in words in 29 CFR 1910.106(a)(19) for storage. A liquid with a flash point above 93 °C (199.4 °F) is not a flammable liquid under that table.

The DOT answer follows 49 CFR 173.120 for Class 3 and combustible liquids and the packing group table in 173.121(a)(1). When the 172.101 Table lists a single packing group for your UN entry, that entry wins over the flash point table, and the tool reminds you of that in the result.

The NFPA 30 class uses the table NFPA published on 17 April 2024, which works in whole Fahrenheit degrees: 73 °F, 100 °F, 140 °F and 200 °F. The tool compares your flash point with those Fahrenheit lines, which is why the class can differ from the OSHA category right at 23 °C.

Conversions use °F = °C × 1.8 + 32, and each result shows both scales. Mixtures of liquids with different volatility need the evaporation test in 173.120(c)(2) before the flash point is final, and this tool takes the number you give it as final.

Worked example. A solvent blend shipped as combustible

The booking. A cleaning solvent blend has a closed cup flash point of 41 °C (105.8 °F) and an initial boiling point of 150 °C. The distributor plans to send it by truck in drums as a combustible liquid, to skip the Class 3 placards, which looks fine on paper.

The failure. At 41 °C the blend is Class 3, packing group III, under 49 CFR 173.121, because its flash point is not more than 60 °C. The reclass to combustible in 173.120(b)(2) is allowed at or above 38 °C, but only for domestic transport, not by vessel. The same drums are also booked on a coastal barge leg. The choice is plain: ship them as Class 3 on that leg, or change the route.

The fix. The shipper keeps the drums as Class 3, PG III, for the barge leg and uses the combustible reclass only on the all road consignments. The SDS shows OSHA category 3 and the warehouse files it as NFPA Class II, since 105.8 °F sits between 100 °F and 140 °F.

Need the GHS pictogram and hazard statements for the label once the category is known? The GHS label maker builds the label from the category.

Frequently asked

What are category 1, 2, 3 and 4 flammable liquids?

They are the four GHS bands in OSHA HCS Appendix B.6. Category 1 has a flash point below 23 °C (73.4 °F) and an initial boiling point at or below 35 °C (95 °F). Category 2 has the same flash point with a boiling point above 35 °C, category 3 runs from 23 °C to 60 °C (140 °F), and category 4 runs above 60 °C up to 93 °C (199.4 °F).

What is the difference between a flammable and a combustible liquid for DOT?

Under 49 CFR 173.120 a flammable liquid (Class 3) has a flash point of not more than 60 °C (140 °F). A combustible liquid has a flash point above 60 °C and below 93 °C (200 °F), and a Class 3 liquid with a flash point at or above 38 °C (100 °F) may be reclassed as combustible for domestic transport, but not by vessel or aircraft unless other means are impracticable.

How does NFPA 30 classify flammable and combustible liquids?

By closed cup flash point, with boiling point used only to split Class IA from IB. The NFPA table sets IA below 73 °F with a boiling point below 100 °F, IB below 73 °F with a boiling point at or above 100 °F, IC from 73 °F to below 100 °F, II from 100 °F to below 140 °F, IIIA from 140 °F to below 200 °F and IIIB at or above 200 °F.

What is a Class 1 flammable liquid?

In NFPA 30 terms, Class I covers liquids with a closed cup flash point below 100 °F (37.8 °C), split into IA, IB and IC. The OSHA HCS and the DOT rules do not use that label. OSHA uses categories 1 to 4 and DOT uses Class 3 with packing groups I to III, so the same liquid carries three different labels on the SDS, the shipping paper and the storage plan.

Does Australia use the same flammable liquid categories?

Safe Work Australia requires manufacturers and importers to classify chemicals to GHS 7 under the model WHS Regulations. OSHA's Appendix B.6 points to GHS Revision 7 chapter 2.6 for its methods, so the category cut points are expected to match, but confirm against GHS 7 chapter 2.6 before you finalise an Australian SDS. Road and rail transport in Australia follows the ADG Code, which this tool does not apply.

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Sourzi shows what official files say. It is not customs or legal advice. For a binding answer, ask a licensed customs broker, a CBP ruling or an Australian Border Force Tariff Advice.

File dates and links are on Data sources.