In the past several weeks I have received inquiries regarding NFPA 704, 4.2.3.2 so I figured I should put it in writing so that others can understand this single clause which apparently has become a “whipping boy” for a particular hazardous material. The quick answer is YES, but apparently, there is some confusion on why NFPA 704, 4.2.3.2 permits this. This is what it says:
4.2.3.2* It shall be anticipated that different physical forms of the material or conditions of storage and use could result in different ratings being assigned to the same material.
*Due to the large number of variables, the requirements and guidance presented in this standard are general in nature and are limited to the most important and common factors. For example, although ash point is the primary criterion for assigning the flammability rating, other criteria could be of equal importance. For example, autoignition temperature, flammability limits, and susceptibility of a container to failure due to fire exposure also should be considered. For instability, the emphasis is on the ease by which an energy releasing reaction is triggered. These factors should all be considered when calling on one’s judgment during the assignment of ratings.
In reality, the same material may have different ratings based on where it is in the process. For example: