NFPA 704

NFPA 704, also known as a Safety Square, is a diamond-shaped sign or picture that tells people about the hazards of a chemical compound.^[1] It was designed in 1960 by the National Fire Protection Association, as a way of quickly telling firefighters and other emergency workers what kind of dangers might be nearby.^[2]

The sign is made of four smaller diamonds: a red one on top, a yellow one on the right, a white one on the bottom, and a blue one on the left. Numbers or symbols in these boxes tell how dangerous the chemical is.

The red diamond tells how flammable the chemical compound is: how easily it catches fire. The yellow diamond tells about reactivity: how quickly the compound reacts with other materials. (For example, some chemicals, like ammonium nitrate, explode when they touch water; this is an example of reactivity.) The blue diamond tells how dangerous the chemical is to a person's health. Each of these three diamonds - red, yellow, and blue - are given a score between 0 and 4. A score of 0 means there is no danger. A score of 4 means there is the worst possible danger.^[3]

The white diamond has codes for "special hazards." For example, if a chemical like ammonium nitrate should not touch water because it will explode, a W with a line through it will be written in the white diamond.^[3]

1. ↑ "NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response". NFPA.org. National Fire Protection Association. 2016. {{cite web}}: Missing or empty |url= (help)
2. ↑ "Proposed Amendments on Revisions to the Recommended System for the Identification of The Fire Hazards of Materials / NFPA No. 704M — 1969" (PDF). Archived from the original (PDF) on 2016-03-03. Retrieved 2016-01-29.
3. ↑ ^{3.0 3.1} "Frequently Asked Questions on NFPA 704" (PDF). NFPA.org. National Fire Protection Association. Archived from the original (PDF) on July 16, 2017. Retrieved January 29, 2016.