NFPA 704 vs GHS
NFPA 704 and GHS both describe chemical hazards, but they are different systems for different audiences. The biggest trap is the scale direction: in NFPA 704 a 4 is the most severe rating, while in GHS Category 1 is the most severe and Category 4 is among the least severe.
Left: NFPA 704 diamond. Right: GHS pictograms for a flammable liquid with a minor health hazard.
Side by side
| Topic | NFPA 704 | GHS |
|---|---|---|
| Who it is for | Emergency responders (fire fighters and others) responding to an incident at a facility or storage area. | Workers, handlers, transporters and consumers who use the chemical day to day. |
| Where it appears | A diamond on buildings, rooms, tanks and storage areas; sometimes copied onto container labels. | On the supplier label of every shipped hazardous chemical, and in Section 2 of the SDS. |
| Scale direction | 0 to 4, where 4 is the most severe. | Category numbers, where Category 1 is the most severe within a hazard class (higher numbers are less severe). |
| Type of hazard covered | Acute health effects of short exposure, flammability, instability, and three special symbols. | A long list of physical, health and environmental hazard classes, including chronic effects such as cancer and aquatic toxicity. |
| Chronic health effects | Not covered by the health number. | Covered (carcinogenicity, mutagenicity, reproductive toxicity, target organ toxicity). |
| Environmental hazards | Not covered. | Covered by the aquatic hazard classes (non-mandatory under OSHA HazCom). |
| Who assigns it | The facility or a qualified person using the standard's criteria; some suppliers publish suggested ratings. | The manufacturer or importer classifies according to the harmonized criteria and must put the result on the label and SDS. |
| Legal status in the US | A consensus standard, adopted through fire codes and local rules. | Required by OSHA HazCom (29 CFR 1910.1200) for labels and SDSs. |
Scale direction
A health rating of 4 on the diamond means a very short exposure could cause death or major lasting injury. A GHS acute toxicity Category 4 means harmful, with an oral LD50 above 300 and up to 2000 mg/kg, which is much less severe than Category 1 (5 mg/kg or less). Reading a GHS Category 4 as if it were an NFPA 4 would overstate the hazard, and reading an NFPA 1 as if it were a GHS Category 1 would understate it.
Example: flammable liquids
Both systems use flash point and boiling point, but the cut-offs are different. The table shows how they overlap. It is approximate, not a conversion.
| GHS category | GHS criteria | Typical NFPA flammability |
|---|---|---|
| GHS Category 1 | Flash point below 23 °C and initial boiling point of 35 °C or below | Usually flammability 4 (when the boiling point is below 38 °C) |
| GHS Category 2 | Flash point below 23 °C and initial boiling point above 35 °C | Usually flammability 3 (flash point below 23 °C, boiling point at or above 38 °C), but a liquid boiling between 35 and 38 °C can fall in NFPA 4 |
| GHS Category 3 | Flash point from 23 °C up to and including 60 °C | Flammability 3 if the flash point is below 38 °C, otherwise 2 |
| GHS Category 4 | Flash point above 60 °C up to and including 93 °C | Flammability 2 |
See the NFPA flammability rating and GHS flammable liquids pages for each system's full criteria.
When you see each one
- GHS: on every supplier label and in SDS Section 2. It is what OSHA HazCom requires.
- NFPA 704: on buildings, rooms, tanks and storage areas, and in the optional fields of SDS Section 16.
- HMIS: on in-plant containers in many US workplaces, often in paint, coatings and cleaning products.
What to do with both
Use the GHS label and SDS to decide how to handle, store and protect yourself when working with a chemical. Use NFPA 704 to understand what responders will expect to see and to plan storage areas. If the two seem to disagree, the SDS data (flash point, toxicity, reactivity) is the tiebreaker, and your safety manager should assign the rating on the diamond. For definitions, see NFPA 704, GHS and hazard category.
Frequently asked questions
Is NFPA 704 the same as GHS?
No. NFPA 704 is a 0 to 4 diamond for emergency responders. GHS is a worldwide system for classifying chemicals and communicating hazards on labels and safety data sheets with pictograms, signal words and hazard statements. They are used for different purposes and assigned under different rules.
Is NFPA 4 or GHS Category 1 worse?
Both are the most severe in their own system. On the NFPA diamond, 4 is the worst rating. In GHS, Category 1 is the most severe category, and higher numbers are less severe.
Can I convert GHS categories to NFPA ratings?
Not reliably. The systems measure different things and use different cut-offs, so there is no official conversion. A facility can use the SDS data (flash point, toxicity, reactivity) and the NFPA 704 criteria to assign a rating.
Does OSHA accept NFPA labels instead of GHS labels?
No, not on shipped containers. OSHA HazCom requires GHS-format labels from the supplier. In the workplace, an employer may use alternative systems such as NFPA 704 or HMIS on in-plant containers only if the information is consistent with HazCom and the employee training covers it.