Burning metals like sodium should not be extinguished with standard fire extinguishers, but they require either sand or a special class D fire extinguisher.

Now, if there is a fire in the lab and the closest fire extinguisher is one of those class D extinguishers meant for metal fires, can those be used for other types of fires?

The main case where there might not be enough time to get specific equipment is probably when people are on fire. Can a class D extinguisher be used in this case, if it's the closest available one?

  • $\begingroup$ Tricky question. There's an important distinction between extinguishers that are safe and effective on non-prescribed fire classes, and extinguishers that are safe to use on living human beings. Many of the Class D formulations sound like they could be highly irritating if they were to come into contact with eyes or mucous membranes (powdered graphite, copper, salts). $\endgroup$ Jun 25, 2012 at 8:59
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    $\begingroup$ That said, getting sprayed with powdered salt is probably preferable to being on fire (unless you're a slug or snail), however that sort of compromise is indicative of a lab safety failure. $\endgroup$ Jun 25, 2012 at 9:15
  • $\begingroup$ If a person is on fire, you should use the safety shower in your lab to extinguish the flames. That is a basic safety rule that should be covered in any lab safety class. $\endgroup$ Jun 25, 2012 at 15:03
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    $\begingroup$ @scientifics Safety showers aren't the only equipment in a lab that can be used to extinguish people on fire, fire blankets and fire extinguishers can be used as well. I would usually choose the shower if I have a choice, my question was more targeted towards situations where that isn't possible for some reason. $\endgroup$ Jun 25, 2012 at 18:43
  • $\begingroup$ @scientifics I would definitely not go into the safety shower to extinguish fire on me if one of the following was true: 1) the safety shower is more than 10 feet away, 2) there are significant obstacles between me and it (stools, litter, people, boxes, etc.), or 3) the fire was stared by a pyrophoric or water reactive substance. In those cases, smothering by the good-old stop-drop-roll method is superior. $\endgroup$
    – Ben Norris
    Jun 28, 2012 at 11:50

1 Answer 1


Unfortunately, as far as I can tell, specific class D fire extinguishers aren't even suitable for all types of class D fire, much less other types of fire.

The copper powder variety in particular has limited effectiveness against fires that aren't lithium-based, and the thermoplastic additives in the sodium chloride-based extinguishers may also catch fire.

Dry sodium carbonate-based class D extinguishers should be generally effective but suboptimal against many types of fire, but I'd say in general, even if you have to go a little further, you should go for the proper sort of extinguisher to minimise accidental horrible disasters.

  • $\begingroup$ This answer is the most dangerous nonsense I have until this day read on SE. The most important consideration in fire fighting is SPEED! Empty the slightly less suitable extintuisher on the fire (they usually last 15 seconds!), THEN fetch something else to make sure the fire doesn't start and spread again. The ONLY extinguisher that really doesn't work is an ABC type against a metal fire. $\endgroup$
    – Karl
    Sep 30, 2018 at 16:33
  • $\begingroup$ @Karl please consider writing that an answer, so that it can be voted upon as well - if you explain what you think is wrong with the accepted answer then it might help convince people, too. Your comment already serves as a warning and generally we don't remove answers simply for being wrong, we downvote them. $\endgroup$ Oct 4, 2018 at 10:40

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