The highest degree of hazard - severe hazard that a very short exposure could cause serious injury or death.
Potential dangers.
240
NFPA 704 for cyclohexane: 1-3-0
The first guide is from 1960.
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.
Fire Hazard: 2, Red square Special Information: 4 Health hazard: 1 Reactivity hazard: 3
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.
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
NFPA codes are enacted selectively, in possibly amended forms, by each state. Similarly, different federal agencies may adopt their own standards or use NFPA standards. For example, OSHA has its own Hazard Communication System (HCS) that is completely different from NFPA 704, using pictograms, being phased in as of December 2013. USDOT also has its own standard for HAZMAT labels (e.g., orange, red, green, yellow, striped, with code numbers and code symbols).
It is the yellow section.