Fire Diamond

Multi-colored fire diamonds, a common fixture on tanks and buildings, are a way of communicating risks quickly to firefighters, and other first responders. They can help determine a number of things like what precautions to take, procedures to follow, and equipment to use.

The fire diamond is part of the Standard System for the Identification of the Hazards of Materials for Emergency Response (NFPA 704). In this type of standard, hazardous chemicals are classified into three principle categories: health, flammability, and instability. Each category is then rated on a scale of zero (least severe hazard) to four (extremely dangerous) and printed in one of four color-coded squares within the diamond:

Blue Square/Health Hazard: Indicates the capability of a material, under emergency circumstances. For example, injury due to skin contact, eye contact, inhalation, or ingestion.

0 – Not hazardous.


1 – Slightly hazardous and can cause significant irritation.

2 – Toxic; can cause temporary incapacitation or residual injury.

3 – Extremely hazardous/highly toxic; can cause serious or permanent injury.

4 – Lethal/deadly

Red Square/Fire Hazard: Represents how susceptive the material is to ignition or burning.

0 – Does not burn

1 – Flash point above 200°F; materials that must be preheated before it can be ignited.

2 – Flash point above 100°F but doesn’t exceed 200°F; materials that must be moderately heated or exposed before ignition can occur.

3 – Flash point below 100°F; materials that can be ignited under almost all ambient temperatures.

4 – Flash point below 73°F; materials that burn readily and can ignite spontaneously.

Yellow Square/Reactivity & Stability Hazard: Represents the degree of hazard based on reaction with air and light.

0 – Stable/non-reactive; substance is not considered explosive

1 – If heated material becomes unstable; substance is considered explosive.

2 – Violent chemical change possible at elevated pressures and temps; substance is considered explosive.

3 –If substantial shock or heat applied, material may detonate; substance is considered explosive.

4 – May detonate; substance is considered very explosive and is readily capable of detonation at normal temperatures.

White Square/Special Hazards: Materials with water reactivity and oxidizing properties cause special problems and typically require special firefighting measures. Typically left blank, but when necessary, the following chemical symbols and acronyms can be used:

ALK – Alkaline

COR-OX – Corrosive Oxidizer

CRY - Cryogenic

OXY – This is the same as OX, it stands for Oxidizer

W (NFPA Approved) – Do not use with water

RAD - Radioactive

Acid – Acid

COR – Corrosive

COR-OXY – Corrosive Oxidizer

OX (NFPA Approved) – Oxidizer

SA (NFPA Approved) - Simple asphyxiant gas

W+OX – Do not use with water, oxidizer


Employers can find the information they need to create fire diamonds in the chemical’s safety data sheet. In addition to NFPA labels, employers will need to comply with OSHA’s Hazard Communication Standard and provide GHS labels and access to Safety Data Sheets (SDS).

OSHA Safety Signs Guide
OSHA Label and Sign Color Chart
HazCom Guide
Other FREE Resources:

Helpful Resources