By Brett Smith, Updated Aug 30, 2022

In the United States, chemical warning symbols are primarily governed by two organizations: the Occupational Safety and Health Administration (OSHA) and the non‑profit National Fire Protection Association (NFPA). Both aim to provide clear, visual cues about the nature of chemical hazards, but they use distinct systems.

OSHA Pictograms

OSHA employs a series of wordless pictograms, each consisting of a black symbol on a white background bordered by a red diamond. These icons convey the core danger posed by a chemical. For example:

• Flame: Indicates the substance may be flammable, self‑heating, self‑reactive, an organic peroxide, or ignitable on air contact.
• Exclamation mark: Signals potential irritant, skin sensitizer, toxic, narcotic, or ozone‑layer‑harmful properties.

NFPA Diamond System

The NFPA uses a single, multi‑colored diamond divided into four smaller triangles, each representing a different hazard category:

• Red (top): Flammability (0–4 scale).
• Blue (left): Acute toxicity (0–4 scale).
• Yellow (right): Reactivity (0–4 scale).
• White (bottom): Special hazards (e.g., strong oxidizer, water reactive).

These symbols serve as quick visual references for safety professionals, ensuring that the risks associated with chemicals are communicated effectively and consistently across industries.