Special hazards (white)
The white section at the bottom of the NFPA 704 fire diamond. It is blank, or holds a symbol for a hazard the numbers don't show: W with a line through it for unusual reactivity with water, OX for an oxidizer, SA for a simple asphyxiant gas.
How to read it
It sits at the six o'clock position of the NFPA 704 fire diamond and carries no number. NFPA's FAQ names W, OX and SA as the only authorized symbols, kept few so the sign stays easy to read in an emergency. the Department of Homeland Security's Center for Domestic Preparedness describes a blank white section as no special hazard. A product can carry two symbols: the same course shows W and OX together for a product that reacts violently with water and is an oxidizer.
Also searched as: nfpa special hazards, nfpa white, white diamond nfpa.
These explain what a rating on the diamond means. For handling, storage and first aid, refer to the product’s label and safety data sheet.
The three symbols
| Symbol | Meaning |
|---|---|
| W with a line through it | Unusual reactivity with water |
| OX | An oxidizer |
| SA | A simple asphyxiant gas, such as nitrogen, helium or argon |
Other letters on real signs
Signs in use carry other markings as well: COR, ACID and ALK for corrosives, acids and alkalis, RAD or the radiation trefoil for radioactive materials, BIO or the biohazard symbol, and CRYO for cryogenic liquids. Sources disagree on their status. NFPA's FAQ, which refers to the 2012 edition, allows only W, OX and SA, and explains that corrosives are already counted in the blue health number. Riverside County calls COR, ACID and ALK non-standard symbols in wide use. The University of Texas at Dallas lists the others as extensions to the standard, and the Department of Homeland Security's Center for Domestic Preparedness, citing the 2007 edition, gives ACID, ALK and COR among seven authorized symbols.
Look-alikes
HMIS labels also end in a white bar, but it holds a letter from A to K, or X, naming personal protective equipment (SUNY Geneseo). On the diamond the white section names a hazard, not equipment.
More NFPA 704 fire diamond
Browse symbols drawn with diamonds or letters and numbers.
Sources
- Frequently Asked Questions on NFPA 704, National Fire Protection Association, published by the Cambridge Fire Department (Massachusetts), Question 5
- NFPA 704 Guidance Document: Frequently Asked Questions (FAQ), EPO-372 (Rev 04/21), Riverside County Department of Environmental Health, Hazardous Materials Management Branch, Page 2
- Hazardous Materials Facility Markings, AWR-358 course, Center for Domestic Preparedness, U.S. Department of Homeland Security
- NFPA 704 Symbols, University of Texas at Dallas, Institutional Risk & Safety
- Hazard Labeling System, SUNY Geneseo, Chemistry Stockroom, Section 2
Last reviewed September 30, 2026 by Rory Hansen. How we research