metalresearcher - 14-1-2022 at 10:34
The NFPA 704 rating of chemicals, displayed in a diamond shaped icon says about :
Blue (left): Toxicity
Red (top): Flammability
Yellow (right): Reactivity
Ratings of each of these three are 0 to 4.
Extra (bottom of 'diamond'): Oxidizing and reacts with water.
The most dangerous is tert-butyllithium, having a scary 4 4 4 rating. https://en.wikipedia.org/wiki/Tert-Butyllithium.
Water has a rating of 0 0 0 which appears to be obvious, as it is harmless to us as long as you not drown. But Water is actually a moderate aggressive
chemical as it reacts (usually slowly) with many relatively harmless substances, e.g. water is one of the worst enemies to a cellphone or other
electronics due to its reactivity of circuit boards.
Actually, water should have a 0 0 2 (2 for reactivity) rating.
Texium - 14-1-2022 at 11:32
Reactivity in the NFPA context generally refers to chemicals that are innately unstable, like explosives, or will react with common substances in a
hazardous way, like strong oxidizers. So that doesn’t apply to water. Things that react with water are labeled as water reactive. It makes more
sense to do that than to ambiguously say that water might react with some substances in a dangerous manner. The 0 0 0 rating is consistent with common
sense.
It’s an obsolete system that’s being phased out anyway, so who cares?