The first guide is from 1960.
240
NFPA 704 for cyclohexane: 1-3-0
0-0-0
The NFPA 704 diamond is a ring of smaller diamonds that are blue, red, yellow and white. A number or symbol in each section indicates the relative danger.
Potential dangers.
The number 4 on the NFPA 704 placard indicates the highest hazard in any of the three categories (health, fire, reactivity).
Health (blue) 2 Fire (red) 0 Reactivity (yellow) 0
Fire Hazard: 2, Red square Special Information: 4 Health hazard: 1 Reactivity hazard: 3
It is the yellow section.
The highest degree of hazard - severe hazard that a very short exposure could cause serious injury or death.
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A "4" in the blue quadrant of NFPA 704 indicates that the substance is known to be highly hazardous to an individual's health. The scale runs from 0 to 4 with 0 being essentially harmless and 4 being extremely harmful or potentially fatal. The number 4 means it is too dangerous to enter the liquid or vapor, as compared with number 3, which means you can work with it if you are fully protected.