this post was submitted on 24 Apr 2025
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106
Any ideas what these signs on this building mean? (lemmy.ml)
submitted 1 day ago by dohpaz42@lemmy.world to c/asklemmy@lemmy.ml
32 comments fedilink hide all child comments
 

Aside of these signs and the address numbers, the building is completely unmarked.

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[–] mic_check_one_two@lemmy.dbzer0.com 15 points 1 hour ago* (last edited 1 hour ago)

Those are hazardous chemical markers. You commonly see them on tanker trucks as well.

The numbers range from 0 to 4, with higher numbers indicating more risk. The red top corner is flammability. The right yellow corner is instability; How likely it is to react with other things around it. The left blue corner is risk to health; Even if a chemical isn’t unstable or flammable, it can still be hazardous. The bottom white is for special markings. In this case, one of those chemicals is marked with a W, meaning it reacts to water.

So if there’s a fire at the warehouse, this tells the responding crew “hey just so you know, there’s some nasty shit in here. One presents a severe health hazard, becomes potentially explosive when heated, and reacts with water… But at least it isn’t flammable. The other is flammable and can present a moderate health risk. Because of the one on the left, it would be a bad idea to use water to fight this fire.”

[–] snugglesthefalse@sh.itjust.works 6 points 1 hour ago (1 children)

Here's my favourite warning, can you guess what it is?

[–] jet@hackertalks.com 153 points 1 day ago* (last edited 1 day ago) (1 children)

Those diamonds indicate what chemical hazards are inside the building, for fire and rescue operations.

https://en.wikipedia.org/wiki/NFPA_704

[–] dohpaz42@lemmy.world 27 points 1 day ago

Thank you!

[–] Blaster_M@lemmy.world 111 points 1 day ago (1 children)

So in that building there's a nonflammable reactant that's super dangerous to life and reacts with water, and a flammable chemical that is quite toxic.

[–] Zombiepirate@lemmy.world 46 points 23 hours ago (2 children)

So... Bring my HEV suit and crowbar?

[–] Yermaw@lemm.ee 31 points 21 hours ago (1 children)

They're waiting for you, OP, in the test. Chamberrrr.

[–] xavier666@lemm.ee 4 points 6 hours ago* (last edited 6 hours ago)

OP doesn't need to hear this. OP's a highly trained professional.

[–] essell@lemmy.world 14 points 23 hours ago

Depends, are you in the tank today?

[–] AbouBenAdhem@lemmy.world 47 points 1 day ago (1 children)

They’re NFPA 704 signs.

[–] dohpaz42@lemmy.world 13 points 1 day ago

Thank you!

[–] queermunist@lemmy.ml 20 points 1 day ago (4 children)

As others have said, these are NFPA signs.

What I want to know is why there are two different ones. What the hell does that mean?

[–] mic_check_one_two@lemmy.dbzer0.com 3 points 55 minutes ago (1 children)

It means there are two separate chemicals inside of the building. Each chemical would have their individual labels on their containers, but these external signs are for first responders who haven’t entered the building yet.

Let’s say there’s a fire. The red diamond tells them how likely it is that the chemicals are the cause of the fire, and where they should direct their efforts. The blue corner tells them what kind of PPE they need to use if they enter. The yellow tells them what kind of potential explosive risks the chemicals have. And the white one is especially important, because the W means the chemical reacts with water; If there’s a fire at the facility, they can’t simply use fire hoses to fight it.

The reason for listing them separately is because each individual chemical has its own ratings. You can’t simply take the highest of each and combine them into a single sign. For instance, in this case one chemical isn’t flammable but is explosive when heated. The other chemical is flammable but not explosive. So if you see a chemical on fire, you know it’s the second chemical and isn’t explosive. But if you see something that isn’t burning in a room full of fire, you know it’s a potential powder keg waiting to explode.

[–] queermunist@lemmy.ml 0 points 42 minutes ago

The reason for listing them separately is because each individual chemical has its own ratings. You can’t simply take the highest of each and combine them into a single sign. For instance, in this case one chemical isn’t flammable but is explosive when heated. The other chemical is flammable but not explosive. So if you see a chemical on fire, you know it’s the second chemical and isn’t explosive. But if you see something that isn’t burning in a room full of fire, you know it’s a potential powder keg waiting to explode.

Okay, so the two signs on the building have a weird combination.

The sign on the left indicates something that isn't flammable, but reacts with water. The sign on the right indicates something that is flammable, but there's no risk of reacting to water. If the building caught fire then a first responder on the scene has to read both signs at the same time. They can't spray the building with water because the non-flammable substance would react with the water.

So why aren't the signs combined? They have to be treated the same anyway.

[–] wolfpack86@lemmy.world 13 points 20 hours ago (1 children)

Section 4.2.3.3 of NFPA 704 guides how to handle multiple chemicals.

You can combine the worst of each category into a composite, list each individually, or do a hybrid option.

The posts saying there are two chemicals are true but likely incomplete... There are probably several different chemicals and they decided to go with the hybrid method.

My guess is that they combined the worst rating of everything that doesn't need special handling, and have a stand alone for the chemical that is incompatible with water (or even combined for several chemicals that are incompatible with water).

[–] queermunist@lemmy.ml 1 points 40 minutes ago* (last edited 18 minutes ago)

That makes sense, but it's still strange because it means in the case of a fire the entire building has to be treated the same anyway because there is something in the building that reacts with water even if its separate.

I guess it is helpful to indicate that there are multiple substances that have different reaction profiles, but it still seems strange to me.

[–] Devadander@lemmy.world 32 points 1 day ago (1 children)

Two different chemicals to be aware of

[–] queermunist@lemmy.ml 5 points 23 hours ago (3 children)

But it's just slapped on the side of the building with no indication of which chemicals the labels are for, I don't think that's how it's supposed to be done. It'd be like mixing two chemicals into a bottle and then putting two labels on it.

I think there should just be one label that combines the warning levels of both i.e. 3-2-2-W

[–] Devadander@lemmy.world 12 points 23 hours ago (1 children)

Why are you assuming the chemicals are mixed together inside the building? Two separate chemicals, two distinct risks.

[–] queermunist@lemmy.ml 3 points 21 hours ago (2 children)

But the building, as a whole, pesents the combined risk of both chemicals.

[–] brygphilomena@lemmy.dbzer0.com 15 points 21 hours ago

First responders need to know that there are two chemicals inside so that they don't stop taking precautions when they encounter the first one.

[–] Cort@lemmy.world 5 points 21 hours ago

They're required to be individually labeled/categorized. And supposed to be on 2 exterior walls, and any doors, and on the containers themselves

[–] Yermaw@lemm.ee 5 points 21 hours ago (1 children)

I'm sure they'll be labelled inside too.

[–] queermunist@lemmy.ml 1 points 21 hours ago* (last edited 21 hours ago) (1 children)

Sure, but I don't think the building should have two labels. I think it should have one label that reflects a warning for everything in the building.

Imagine you have a crate with two different chemicals. The chemicals are in different bottles so they aren't mixed, and each bottle has its own label.

Should the crate have two unidentified labels like this, or one? There's no indication what those labels refer to on the building.

[–] desktop_user@lemmy.blahaj.zone 0 points 5 hours ago

if the chemicals are extremely different in hazard it could be useful to know that it's not a mixture, like a superacid and a strong base.

[–] Horse@lemmygrad.ml 5 points 23 hours ago (1 children)

i would hope that there would be labels inside the building that would indicate which is which, but who fucking knows with the us lol

[–] NakariLexfortaine@lemm.ee 4 points 23 hours ago

They generally have them on the containment units, and if they're used elsewhere, on the pipes/machines carrying/using the chemicals.

Now, if they've been properly replaced since installation is a completely different question. I've seen far too many faded/shredded diamonds on the sides of things.

[–] spizzat2@lemm.ee 12 points 23 hours ago (1 children)

I'm no expert, so I can't tell for sure, but my guess is that they're storing two different chemicals. The left one looks like it's a non-flammable, extremely hazardous material that shouldn't be exposed to water (maybe an alkali metal, like lithium or sodium). The right one is a hazardous material that is a fire hazard above 93°C (200°F), but otherwise stable (maybe some kind of diesel?)

So... If I had to take a wild guess, diesel and lithium batteries?

[–] GreyEyedGhost@lemmy.ca 5 points 14 hours ago

Reading this made me wonder how metallic lithium is stored and, guess what, it's stored in oil. So, which label do you use for a container holding lithium and oil? I'm guessing you need two, one for the lithium and one for the oil. And here we are.

No, I don't think this building is filled with lithium and covered in oil, but I suspect there is more than one container containing metallic lithium covered in oil.

[–] ShellMonkey@lemmy.socdojo.com 14 points 1 day ago

Similar to the markings used on trucks hauling hazardous materials. Might be for the fire dept if the place goes up in flames.

[–] originalucifer@moist.catsweat.com 11 points 1 day ago (1 children)

https://risk-safety.utdallas.edu/fire-prevention-and-protection-programs/nfpa-704-symbols/

[–] dohpaz42@lemmy.world 5 points 1 day ago

Thank you!