OX (oxidizer)
On an NFPA 704 fire diamond, OX in the white section at the bottom marks an oxidizer: a material that can supply oxygen, so that other materials burn.
Easily confused with
How to read it
It is one of the three special hazard symbols of the NFPA 704 fire diamond. CAMEO Chemicals defines it as materials that possess oxidizing properties. the Department of Homeland Security's Center for Domestic Preparedness puts it as a material that, by providing oxygen, can cause other materials to burn, and the University of Texas at Dallas says it allows other chemicals to burn without an air supply. Riverside County gives potassium perchlorate, ammonium nitrate and hydrogen peroxide as examples, and CAMEO Chemicals rates chlorine 4 for health, 0 for flammability and 0 for instability, with OX. Some signs write it OXY. The details are on the product's safety data sheet.
Also searched as: nfpa ox, ox symbol.
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.
Look-alikes
On GHS container labels the oxidizer pictogram is the flame over a circle, which Britain's Health and Safety Executive names Oxidising. The flame alone, named Flammable, is a different hazard. On the diamond an oxidizer's own flammability number can be 0, as chlorine's is; the OX says that it feeds a fire.
More NFPA 704 fire diamond
Browse symbols drawn with letters and numbers.
Sources
- NFPA Diamond (CAMEO Chemicals help), NOAA Office of Response and Restoration
- CHLORINE (CAMEO Chemicals datasheet), NOAA Office of Response and Restoration, Chemical Identifiers: NFPA 704
- 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
- NFPA 704 Guidance Document: Frequently Asked Questions (FAQ), EPO-372 (Rev 04/21), Riverside County Department of Environmental Health, Hazardous Materials Management Branch, Page 1
- Frequently Asked Questions on NFPA 704, National Fire Protection Association, published by the Cambridge Fire Department (Massachusetts), Question 5
- Hazard pictograms (symbols), GB CLP, Health and Safety Executive (Great Britain)
- Comparison of NFPA 704 and HazCom 2012 Labels (Quick Card), National Fire Protection Association and U.S. Occupational Safety and Health Administration
Last reviewed September 30, 2026 by Rory Hansen. How we research