# AMMONIA, ANHYDROUS — NFPA 704 fire diamond ratings by chemical

For AMMONIA, ANHYDROUS, cas number is 7664-41-7; health (blue) is 3; flammability (red) is 1; instability (yellow) is 0; what the rating means is Health | 3 | Can cause serious or permanent injury. | Flammability | 1 | Must be preheated before ignition can occur. | Instability | 0 | Normally stable, even under fire conditions. | Special | | | Note: The Refrigeration System Classification section of the International Mechanical Code requires a value of 3 for the red quadrant (flammability hazard) for indoor ammonia refrigeration equipment, verified against its source on 2026-08-06.

- **Chemical:** AMMONIA, ANHYDROUS _(verified: appears in the quote below)_
- **CAS number:** 7664-41-7 _(verified: appears in the quote below)_
- **Health (blue):** 3 _(verified: appears in the quote below)_
- **Flammability (red):** 1 _(verified: appears in the quote below)_
- **Instability (yellow):** 0 _(verified: appears in the quote below)_
- **What the rating means:** Health | 3 | Can cause serious or permanent injury. | Flammability | 1 | Must be preheated before ignition can occur. | Instability | 0 | Normally stable, even under fire conditions. | Special | | | Note: The Refrigeration System Classification section of the International Mechanical Code requires a value of 3 for the red quadrant (flammability hazard) for indoor ammonia refrigeration equipment. _(verified: appears in the quote below)_

## What the source says

> Health | 3 | Can cause serious or permanent injury. | Flammability | 1 | Must be preheated before ignition can occur. | Instability | 0 | Normally stable, even under fire conditions. | Special | | | Note: The Refrigeration System Classification section of the International Mechanical Code requires a value of 3 for the red quadrant (flammability hazard) for indoor ammonia refrigeration equipment.

## Source

- https://cameochemicals.noaa.gov/chemical/4860

Last verified: 2026-08-06. Review by: 2028-08-05.
Part of [NFPA 704 fire diamond ratings by chemical](https://referencesource.org/nfpa-704-hazard-ratings/).