Why Ethanol has the blue health hazard rating of 2 in NFPA 704 where as both Acetone and Methanol which are far more toxic than Ethanol have a rating of only 1? (Click on each link to see the NFPA diamond)

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    $\begingroup$ it's the "fire diamond", F in NFPA states for fire hazard. Anyway, the health info (blue) difference is strange. $\endgroup$
    – mykhal
    Apr 28, 2017 at 7:55

1 Answer 1


I believe that the rating is dependent on toxicity tests.

The acute oral toxicity LD50 value of acetone is 5800 mg/kg

The acute oral toxicity LD50 value of methanol is 5628 mg/kg

The acute oral toxicity LD50 value of ethanol is 3450 mg/kg

Low LD50 values means that only a small amount of chemical is needed to kill someone. According to these values, you would need to ingest a larger amount of acetone or methanol to die.I am not sure how valid these toxicology test are. Fun fact: fructose is deadlier than methanol according to LD50 values.

Furthermore, there appears to be some variation in the values as well. Wikipedia lists the LD50 value of ethanol as 7,060 mg/kg. Maybe this question can be addressed at Biology SE.

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    $\begingroup$ LD 50 is a rotten metric for the relative toxicity of methanol and ethanol. This might be because methanol kills you slowly and its acute toxicity isn't the one that matters. $\endgroup$
    – matt_black
    Apr 28, 2017 at 10:33

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