GHS, NFPA 704, DOT and the fire code, decoded.
Pick a hazard statement from a safety data sheet, a pictogram from a label, a number from an NFPA 704 diamond or a DOT hazard class, and see what it means in each of the other three systems: where they line up, where the answer turns on the flash point or the LD50, and where they do not map at all. Every statement, class and line is read from OSHA, the UN GHS, DOT's regulations and NOAA, never retyped. Free from FireInspection360, the fire prevention platform built by fire inspectors.
What does it mean in the other three systems?
The same number means different things in each system, and some hazards have no counterpart at all. Start from whatever is in front of you.
49 CFR 173.120
- DOT What you picked
- GHS It depends
- NFPA 704 Its own scale
- IFC It depends
DOT (transport)
What you pickedClass 3: Flammable and combustible liquid
Defined in 49 CFR 173.120.
"For the purpose of this subchapter, a flammable liquid (Class 3) means a liquid having a flash point of not more than 60 °C (140 °F), or any material in a liquid phase with a flash point at or above 37.8 °C (100 °F) that is intentionally heated and offered for transportation or transported at or above its flash point in a bulk packaging …"
49 CFR 173.120(a)
"Packing group (PG) is the degree of danger: I is great danger, II medium, III minor (49 CFR 171.8)."
49 CFR 171.8
GHS (OSHA Hazard Communication)
It dependsCategory 1, 2 or 3, flammable liquids
- Category 1 Packing Group I: when its flash point is below 73.4°F (23°C)
- Category 3 Packing Group I: when its flash point is 73.4°F (23°C) to 140°F (60°C)
- Category 2 Packing Group II: every liquid in it
- Category 3 Packing Group III: every liquid in it
- H206 Fire, blast or projection hazard; increased risk of explosion if desensitizing agent is reduced the GHS also sends Desensitized explosives, Category 1 under Class 3 or Division 4.1
- H208 Fire hazard; increased risk of explosion if desensitizing agent is reduced the GHS also sends Desensitized explosives, Category 4 under Class 3 or Division 4.1
- H207 Fire or projection hazard; increased risk of explosion if desensitizing agent is reduced the GHS also sends Desensitized explosives, Category 2 and Desensitized explosives, Category 3 under Class 3 or Division 4.1
"1-most severe hazard 4-least severe hazard"
OSHA QuickCard 3678-08 2013
NFPA 704 (the diamond)
Its own scaleThe red and yellow quadrants, by NFPA 704's own criteria
The red (flammability) quadrant rates how readily the material burns.
The yellow (instability) quadrant rates how readily the material detonates, decomposes or reacts violently on its own.
"The hazard category numbers found in section 2 of the HC2012 compliant SDSs are NOT to be used to fill in the NFPA 704 diamond."
OSHA QuickCard 3678-08 2013
"Section 2 on an SDS requires hazard category numbers that may look similar to NFPA values, but they are not the same. In fact, the HCS uses a hazard numbering system that is the reverse of the NFPA system; in the HCS system a 1 is the most hazardous number and a 4 is the least hazardous."
NOAA CAMEO Chemicals
IFC (the fire code)
It dependsClass IA, IB, IC or II
The IFC draws its flash point lines in Fahrenheit, at 73°F, 100°F, 140°F and 200°F, and splits Class IA from IB at a boiling point of 100°F. The GHS and DOT draw theirs in Celsius.
- Flammable liquid, Class IA Packing Group I: when its flash point is below 73°F What one control area may hold of it
- Flammable liquid, Class IC Packing Group I: when its flash point is 73°F to below 100°F What one control area may hold of it
- Flammable liquid, Class IA Packing Group II: when its flash point is below 73°F and its boiling point is above 95°F (35°C) and below 100°F What one control area may hold of it
- Flammable liquid, Class IB Packing Group II: when its flash point is below 73°F and its boiling point is at or above 100°F What one control area may hold of it
- Flammable liquid, Class IC Packing Group II: when its flash point is 73°F to below 73.4°F (23°C) (the two lines are less than a degree apart) What one control area may hold of it
- Flammable liquid, Class IC Packing Group III: when its flash point is 73.4°F (23°C) to below 100°F What one control area may hold of it
- Combustible liquid, Class II Packing Group III: when its flash point is 100°F to below 140°F (60°C) What one control area may hold of it
- Combustible liquid, Class IIIA Packing Group III: when its flash point is exactly 140°F What one control area may hold of it
Flash point (°F)
- Category 1: boiling point at or below 95°F (35°C)
- Category 2: boiling point above 95°F (35°C)
- Class 3, Packing Group I: boiling point at or below 95°F (35°C)
- Class 3, Packing Group II: boiling point above 95°F (35°C)
- Class 3, Packing Group III: boiling point above 95°F (35°C)
- Flammable liquid, Class IA: boiling point below 100°F
- Flammable liquid, Class IB: boiling point at or above 100°F
- Combustible liquid, Class IIIB (flash point at or above 200°F) has no GHS category and no DOT class.
- NFPA 704 rates flammability by the criteria of its own Table 6.2 (OSHA QuickCard 3678), which no public source prints, so it has no row here.
From OSHA, 29 CFR 1910.1200 Appendix C (label elements); OSHA, Appendix B (physical hazard criteria) and Appendix A (health hazard criteria); The UN GHS, Rev. 11, 2025, as PubChem summarizes it (H-codes, transport classes, pictograms); eCFR, 49 CFR 173.2, 173.120, 173.121 and 173.133, as of 2026-09-24; NOAA CAMEO Chemicals, NFPA Diamond; OSHA QuickCard, Comparison of NFPA 704 and HazCom 2012 Labels (OSHA 3678-08 2013). The code, the standard and the regulations your jurisdiction has adopted govern.
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Four systems describe the same chemical for four different readers, and their numbers run in different directions.
The GHS, as OSHA's Hazard Communication Standard adopts it, labels a chemical for the people who work with it: "Informs workers about the hazards of chemicals in workplace under normal conditions of use and foreseeable emergencies." NFPA 704 marks a building for the people who respond to it: "Provides basic information for emergency personnel responding to a fire or spill and those planning for emergency response." (OSHA QuickCard 3678-08 2013). DOT's hazard classes decide how a material is packaged, labelled and placarded for transport. The International Fire Code's hazard categories decide how much of it a building may hold and what it takes to keep it there.
The numbers are the trap. In the GHS a category runs "1-most severe hazard 4-least severe hazard"; in NFPA 704 "0-least hazardous 4-most hazardous" (OSHA QuickCard 3678-08 2013). NOAA puts it this way: "Section 2 on an SDS requires hazard category numbers that may look similar to NFPA values, but they are not the same. In fact, the HCS uses a hazard numbering system that is the reverse of the NFPA system; in the HCS system a 1 is the most hazardous number and a 4 is the least hazardous." A DOT class number names the kind of hazard, never its degree; the degree is the packing group ("Packing group (PG) is the degree of danger: I is great danger, II medium, III minor (49 CFR 171.8)."). And the fire code's classes carry their own numbers again.
So this page never converts one number into another. Where two systems draw lines on the same measurement, the flash point and boiling point of a liquid or the LD50 of a poison, it lays their lines side by side and says exactly where a category of one lands in the other, down to the tenth of a degree where a line drawn in Celsius meets one drawn in Fahrenheit. A liquid always flashes below the temperature it boils at, so a combination that would need the reverse is left out. Everywhere else the GHS's own allocation table names the transport class that goes with a category, and FireInspection360's fire code classifier, the same one its SDS reader runs, says what the fire code makes of a statement, a class or a rating on its own.
NFPA 704's criteria are NFPA's own ("Within the blue, red, and yellow quadrants a number from 0 to 4 indicates the degree of risk associated with the chemical. The higher the number, the higher the risk.", NOAA), and no public source prints them, so the page says which quadrant would rate a hazard of a given kind and never which number it would get. "The hazard category numbers found in section 2 of the HC2012 compliant SDSs are NOT to be used to fill in the NFPA 704 diamond." (OSHA QuickCard 3678-08 2013)
Chemicals in FireInspection360
FireInspection360 reads a safety data sheet into the IFC hazard categories, keeps each chemical on the property it is stored at, adds a control area up against its maximum allowable quantities and draws the building's combined NFPA 704 diamond from what is on site.
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