I've searched on a lot of websites if elemental mercury (Hg) has an NFPA classification but I can't find any.

Does mercury have an NFPA classification?


2 Answers 2


According to Sigma-Aldrich

Some symbols:

  • GHS06: Acute toxicity (oral, dermal, inhalation), categories 1,2,3

  • GHS08: Respiratory sensitization, category 1; Germ cell mutagenicity, categories 1A,1B,2; Carcinogenicity, categories 1A,1B,2; Reproductive toxicity, categories 1A,1B,2; Specific Target Organ Toxicity – Single exposure, categories 1,2; Specific Target Organ Toxicity – Repeated exposure, categories 1,2; Aspiration Hazard, category 1

  • GHS09: Hazardous to the aquatic environment; Acute hazard, category1; Chronic hazard, categories 1,2

And according to ScienceLab:

  • Health: 3
  • Fire: 0
  • Reactivity: 0

I believe the ScienceLab information is the 'NFPA 704 classification'.


An email exchange between NIST and myself asking for clarifiation:

My Email (Pre-filled form on the website, I don't have the original):

Something along the lines of "Hello, I see NIST and a few other manufactures
of have different NFPA classifications (I provided links to the SDS's), 
could you explain the difference between your ratings and theirs?"

Their response:

Good afternoon,
Our NFPA rating Health = 2 Fire = 0 Reactivity = 0 matches other manufacturers.
You can check Aldrich website for 99.99 Mercury

Thank you,
Office of Reference Materials

Other manufacturers (Note, plural) apparently now equals 1 example

  • $\begingroup$ But see the link in my comment to the OP. Both NIST and NIOSH have values that disagree with the ScienceLab value, and Sigma-Aldrich gives a value of 4 on one of their MSDS's and a value of 2 on one of their SDS's. Is there a good reason to believe any of these, or the ScienceLab value you give, above another? $\endgroup$
    – airhuff
    May 19, 2017 at 21:41
  • $\begingroup$ @airhuff Yes, I saw. I actually just sent an email to NIST with the links asking if they could explain their rationale on their rating vs. the others, I'll update my answer and comment there if they respond with anything relevant. I figure they're probably the most unbiased and knowledgable on the matter. $\endgroup$ May 19, 2017 at 21:44
  • $\begingroup$ Awesome idea. I hope you get a response and look forward to seeing a good reason for this disparity. Thx for your response to my comment. $\endgroup$
    – airhuff
    May 19, 2017 at 21:49
  • $\begingroup$ @airhuff They responded, but their response doesn't help at all, and the tone makes me think that they think I'm stupid for asking such a question. The email in full is in the answer above. $\endgroup$ May 22, 2017 at 17:54
  • $\begingroup$ Well, nice try. I didn't read that they were condescending, just incompetent in their answer. No explanation of why the disagreement in the links you sent? Pretty weak effort on their part. $\endgroup$
    – airhuff
    May 22, 2017 at 18:31

according the Federal Final Rule of hazard Communication Mercury has a NFPA rating of 0 because it does not burn.

  • 1
    $\begingroup$ NFPA has four ratings for everything... $\endgroup$
    – MaxW
    Feb 18, 2017 at 19:04
  • $\begingroup$ Yeah according to Wikipedia NFPA has 4 ratings : Health, Stability, Flammability, and special $\endgroup$
    – creekorful
    Feb 18, 2017 at 19:23
  • 3
    $\begingroup$ my apologies, there are 4 ratings (flammability, health, reactivity, and special notice) there is no special notice so it rates as follows: health hazard: 3, fire hazard: 0, and reactivity hazard: 0. Mercury was given these ratings because as you may be aware it is a stable metal, does not burn, and is a serious health risk if in contact with or if ingested. $\endgroup$ Feb 18, 2017 at 20:40
  • $\begingroup$ Thank for the information but MaxW answer show that Mg have a level 4 for the health risks. Don't know why but all the informations aren't the same $\endgroup$
    – creekorful
    Feb 18, 2017 at 21:45

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