# Nuisance Dust in fire extinguishers? **URL:** \ **Category:** Factual Questions\ **Created:** [October 31, 2001, 12:00am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628 "2001-10-31T00:00:14Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![FyreFiend](https://avatars.discourse-cdn.com/v4/letter/f/919ad9/32.png) [@FyreFiend](https://boards.straightdope.com/u/FyreFiend)\ **Post date:** [October 31, 2001, 12:00am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/1 "2001-10-31T00:00:14Z")
Hello, We had a small electrical fire in our kitchen today that I put out with a small fire extinguisher. Thankfully everyone’s alright and there was no real damage. Right now we’re cleaning up the mess left over from fire extinguisher. My mother calls the fine power mess “Nuisance Dust” and I thought it was a name she had come up with but reading the contents of the extinguisher it lists Nuisance Dust after a bunch of flame arresting chemicals. So, What is this Nuisance Dust and what’s it for? ---
**Author:** ![Cargogal](https://avatars.discourse-cdn.com/v4/letter/c/48db29/32.png) [@Cargogal](https://boards.straightdope.com/u/Cargogal)\ **Post date:** [October 31, 2001, 12:03am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/2 "2001-10-31T00:03:32Z")
I believe Nuisance Dust refers to substances that are not toxic, and whose sole danger rests in the irritation they cause upon being inspired. ---
**Author:** ![Toaster](https://avatars.discourse-cdn.com/v4/letter/t/7bcc69/32.png) [@Toaster](https://boards.straightdope.com/u/Toaster)\ **Post date:** [October 31, 2001, 12:08am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/3 "2001-10-31T00:08:34Z")
Better not show them the motivational posters then! ---
**Author:** ![Lagged2Death](https://avatars.discourse-cdn.com/v4/letter/l/ac8455/32.png) [@Lagged2Death](https://boards.straightdope.com/u/Lagged2Death)\ **Post date:** [October 31, 2001, 12:23am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/4 "2001-10-31T00:23:18Z")
> [@](#): > > \*Originally posted by FyreFiend \* > \*\*Hello, > Right now we’re cleaning up the mess left over from fire extinguisher… So, What is this Nuisance Dust and what’s it for? \*\* Probably to make a mess, to discourage people from casually expending the fire extinguisher for a joke or other horseplay. Also to leave evidence behind that such fooling about might have happened - even if the miscreant isn’t caught in the act, the mess makes it clear that the extinguisher needs to be recharged. These are only guesses, though. ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [October 31, 2001, 12:25am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/5 "2001-10-31T00:25:59Z")
The last couple of BC fire extinguishers I looked at closely had, in addition to Nuisance Dust, an ingredient identified as “Irritant.” I’m guessing that it’s a similar thing, but I’m having trouble deciding just what the difference between the two is… ---
**Author:** ![Cargogal](https://avatars.discourse-cdn.com/v4/letter/c/48db29/32.png) [@Cargogal](https://boards.straightdope.com/u/Cargogal)\ **Post date:** [October 31, 2001, 12:38am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/6 "2001-10-31T00:38:32Z")
They put my sister in a fire extinguisher?? 🙂 ---
**Author:** ![brad\_d](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@brad\_d](https://boards.straightdope.com/u/brad_d)\ **Post date:** [October 31, 2001, 1:18am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/7 "2001-10-31T01:18:20Z")
Actually, I have one right here with me. It’s a First Alert Dry Chemical Fire Extinguisher, Classification 5:B-C. The punctuation of the ingredients list is kind of strange (periods and commas are used seemingly interchangeably), so I’ll reproduce it verbatim: > [@](#): > > Filled with Plus-Fifty C[sup]®[/sup] Sodium Bicarbonate Dry Chemical Powder. HMIS 1-0-0. Talc, Magnesium Aluminum Silicate, Nuisance Dust. Irritant. ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [October 31, 2001, 2:02am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/8 "2001-10-31T02:02:28Z")
For some reason certain harmless substances like sodium bicarbonate will put out fires when they’re finely divided. I think it has something to do with being an inert substance (meaning one that won’t burn) with a lot of surface area. Anyway, if you look at material safety data sheets for all kinds of finely-divided, harmless substances, like calcium carbonate or titanium dioxide intended for use in paint, they will all say, “Nuisance dust.” That means that they’re non-toxic, but they’re so finely divided that they’ll float in the air and be irritating if you inhale them. In the case of the fire extinguisher ingredients, I **think** the phrase “nuisance dust” is intended to describe the hazard associated with the ingredients. That’s why **brad’s** ingredient list, with its notably weird punctuation, says, **Talc, Magnesium Aluminum Silicate, Nuisance Dust. Irritant.** When it says “nuisance dust” and “irritant,” those are just meant to describe the hazardous properties of finely divided talc and magnesium aluminum silicate. ---
**Author:** ![DMC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dmc/32/18049_2.png) [@DMC](https://boards.straightdope.com/u/DMC)\ **Post date:** [October 31, 2001, 3:09am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/9 "2001-10-31T03:09:52Z")
From [here](http://www.acgih.org/Products/tlvintro.htm): > [@](#): > > Particulates (Insoluble) Not Otherwise Specified (PNOS). There are many substances with TLVs and many more without TLVs for which there is no evidence of specific toxic effects. Those that are particulates have frequently been called “nuisance dusts.” Although these materials may not cause fibrosis or systemic effects, they are not biologically inert. At high concentrations, otherwise nontoxic particulates have been associated with the occasionally fatal condition known as alveolar proteinosis. At lower concentrations, they can inhibit the clearance of toxic particulates from the lung by decreasing the mobility of the alveolar macrophages. Accordingly, the Chemical Substances TLV® Committee recommends the use of the term “Particulates (Insoluble) Not Otherwise Specified (PNOS)” to emphasize that all materials are potentially toxic and to avoid the implication that these materials are harmless at all exposure concentrations. Particulates identified under the PNOS heading are those containing no asbestos and \< 1% crystalline silica. To recognize the adverse effects of exposure to otherwise nontoxic particulate matter, a TLV-TWA of 10 mg/m3 for inhalable particulate and a TLV-TWA of 3 mg/m3 for respirable particulate have been established and are included in the Adopted TLV® section. Refer to the PNOS Documentation for a complete discussion of this subject. ---
**Author:** ![Popup](https://avatars.discourse-cdn.com/v4/letter/p/94ad74/32.png) [@Popup](https://boards.straightdope.com/u/Popup)\ **Post date:** [October 31, 2001, 8:58am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/10 "2001-10-31T08:58:50Z")
> [@](#): > > \*Originally posted by Bob Scene \* > **For some reason certain harmless substances like sodium bicarbonate will put out fires when they’re finely divided. I think it has something to do with being an inert substance (meaning one that won’t burn) with a lot of surface area.** It is actually more ingenious than that! When sodium bicarbonate is heated it releases carbon dioxide. This can either be used to make a fluffy sponge cake, or to extinguish a fire. ([cite](http://www.food.us.rhodia.com/brochures/sodiumbicarb/page3.asp#Fire)) ---
**Author:** ![Bob\_Scene](https://avatars.discourse-cdn.com/v4/letter/b/e19adc/32.png) [@Bob\_Scene](https://boards.straightdope.com/u/Bob_Scene)\ **Post date:** [October 31, 2001, 11:06am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/11 "2001-10-31T11:06:32Z")
> [@](#): > > \*Originally posted by tc \* > \*\*[It is actually more ingenious than that! > When sodium bicarbonate is heated it releases carbon dioxide. This can either be used to make a fluffy sponge cake, or to extinguish a fire. ([cite](http://www.food.us.rhodia.com/brochures/sodiumbicarb/page3.asp#Fire)) \*\* That’s true, but some fire extinguishers have compounds in them that (I think) are really inert to heat, like ammonium phosphate and potassium chloride. I don’t know how they work or what makes them better than the bicarbonate ones, but I think it has something to do with interrupting the complex combustion reactions, which I think is just a property of being a fine powder. ---
**Author:** ![FyreFiend](https://avatars.discourse-cdn.com/v4/letter/f/919ad9/32.png) [@FyreFiend](https://boards.straightdope.com/u/FyreFiend)\ **Post date:** [October 31, 2001, 9:46pm UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/12 "2001-10-31T21:46:14Z")
Thanks all. Very informative. ---
**Author:** ![bradley\_s](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bradley_s/32/16145_2.png) [@bradley\_s](https://boards.straightdope.com/u/bradley_s)\ **Post date:** [February 10, 2024, 1:09am UTC](https://boards.straightdope.com/t/nuisance-dust-in-fire-extinguishers/90628/13 "2024-02-10T01:09:50Z")
> [@brad\_d](#): > > The punctuation of the ingredients list is kind of strange (periods and commas are used seemingly interchangeably), I believe the punctuation here is actually very deliberate. Commas separate the ingredients and periods are separating each ingredient from remarks. I think their intent is for it to read more like this: > Filled with: > > - Plus-Fifty C® Sodium Bicarbonate Dry Chemical Powder (HMIS 1-0-0) > - Talc (Magnesium Aluminum Silicate) > - Nuisance Dust (Irritant) Although all of the ingredients could be considered irritants, nuisance dust is added specifically to play the role of irritant. Typically it is a mixture of limestone and titanium dioxide. It seems inconsistent that they list the chemical composition of talc but not that of their nuisance dust.