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CONYERS, Ga. — A chemical cloud has been emanating from Conyers since Sunday, when a fire broke out at the facility of a company that makes pool and spa treatments and sprinkler system water reacted with chemicals on site. The city of Conyers was evacuated, the wider Rockdale County was put under shelter-in-place guidance and surrounding counties for a time reported the smell of chlorine and a haze in areas.

The chemical plume has put residents in Rockdale County into a shelter-in-place order from officials from 7 p.m. until 7 a.m. until Friday, Oct. 4.

On Tuesday, 11Alive meteorologist Melissa Nord sat down and spoke with Georgia Tech chemistry professor, Dr. Joseph Sadighee, who explained just exactly what is lingering in the air over the Conyers BioLab plant.

QandA on Conyers chemical plume

Question 1

Q: There have been a lot of people wondering about chlorine in the air over the last several days with this BioLab fire that happened on Sunday, and since then, there is still a plume of smoke that is over or chemicals that are over Conyers and surrounding areas as well. Now, for the every average day person who doesn't have any science knowledge, can you very shortly explain what chlorine is versus different chlorine compounds?

A: Yes, I'd be happy to. So chlorine is an element that is very common in everyday life. Table salt is sodium chloride, which means it's chlorine that has picked up an electron and it's in a salt lattice that makes it very, very stable. If you run an electrical current through it, you can turn it into chlorine gas, that's a molecule made up of two chlorine atoms, and it is a gas under ordinary conditions.

If we have it in a cylinder under pressure, uh at about eight atmospheres and room temperature, you have a liquid under the pressure of its own headspace like we do in, in propane gas cylinders for our grills. Chlorine gas is very poisonous in high concentrations. It was the first substance used in chemical warfare during World War I. Now, I don't want to alarm anybody that was used deliberately at very high concentrations.

At lower concentrations, it's used as a bleaching and disinfection agent. So, if you've been to a public pool, you've smelled chlorine in the air at concentrations far below what would do you any harm.

Question 2

Q: That was a really great basic way of breaking it down. Now, we know BioLab was producing a lot of different chlorine compounds for pool treatment to sanitize pools. But they didn't give a lot of specifics in the press conferences of which specific compounds were stored in that factory that caused the initial fire. But we know when the fire broke out the fire, sprinklers went off and that caused a bigger reaction. How can that happen?

A: There are a lot of chemicals that will react with water to liberate heat by themselves or to generate products that can then feed the fire. So, without knowing exactly what they had on hand, I can't. I don't want to speculate, but I will say that it's not surprising to me that that happens. There are lots of things in my lab that we have to make absolutely sure never get wet.

Question 3

Q: And in one of the lawsuits filed today, there were a couple different lawsuits filed today against BioLab, they listed a chemical that was produced at BioLab as Trichloroisocyanuric Acid.

A: Trichloroisocyanuric Acid, and that is a mouthful, but that is one of the solid chlorine precursors that are sold as pool chlorine tablets. As I said, chlorine is a gas, or you can keep it as a liquid under pressure. But those who don't want to have a cylinder of pure chlorine around, which is very dangerous. find it more convenient to have a bucket of these tablets of this chlorine compound that decomposes in water to give very slow release of active chlorine.

Question 4

Q: Now you said it's put it, it's slow releases in water. OK. What, what if it only came in contact with a small amount of water? Would that change the state that it's in?

A: It's such a great question because before speaking to you, I looked into what they might have on hand and I found this compound and I looked up the safety data sheet, which is something they keep for any chemical that's commercially available. And that safety data sheet states never allow a small amount of water to go into a large amount of material. Always add this product to a large amount of water.

Question 5

Q: Wow. Wow. In the press conference this morning at 10 o'clock, they were saying that they still had a lot of Trichloric Acid off-gassing and that will keep happening through the week until all the chemicals are removed. What is that process, off-gassing? What is that?

A: So, I'm guessing Trichloric Acid is maybe a nickname for that much more complicated name before and off-gassing is kind of a slang term for any process that's going to release a harmful gas. Maybe it's a liquid that's giving more vapor as it warms up, or maybe in this as in this case, it's a solid that's going to react with water and give off more gasses over time. So my guess is that they know they still have some product on hand and they can't be sure it's done releasing chlorine.

Question 6

Q: So that might be still going through some kind of reaction where it's going from those solid, just speculating here, the solid tablets to a vapor form. So maybe that vapor trail that we're seeing, that's kind of the off effect of that reaction happening?

A: That would be my guess.

Question 7

Q: OK. Now, if you had TCC A, this chemical that we're talking about in your lab, what would be the proper PPE -- personal protective equipment you would use when handling that?

A: Right. Great question. So, these tablets are very stabilized. The whole reason that they chose this chemical is that as long as it's stored properly and handled properly, it's fairly inert, it's not imminently dangerous. It's just under certain circumstances, it can become dangerous. So, if I were handling these tablets in the lab, just as if I were handling them for a swimming pool, I would probably wear gloves because they could irritate my skin.

I would wear goggles because I don't want to get anything in my eyes. So we always wear goggles, but there's really no harm, no hazard in dealing with these as long as they're under normal circumstances. And I think the reason they're a problem now is that we're so far out of the normal range of how they're handled. If they're exposed to a fire, if they're exposed to sprinklers, then normal bets are off.

Question 8

Q: And if a fire breaks out and you know, you have a chemical compound that doesn't wanna go with a little bit of water, um, and it creates a reaction. How do you fight or would you if that happened in a lab, what would be the process of putting out a fire like that for something that's hydrophobic, doesn't like water?

A: In my view, when you have something that can't contact water, if a fire were to happen, it's important to design your lab so that it won't contact water. In other words, if water has to be used to fight the fire, you have to ask, 'OK, how do we make sure that it doesn't contact this material?' In my lab, we have small amounts of water and reactive chemicals. We keep them apart from everything else. And if we had a fire, we would advise the fire department not to use water. That might be a luxury that we have that a large plant does not have right with that large of quantity of material that doesn't like water.

Question 9

Q: Let's go back to the basics. You said chlorine. Chlorine, in its purest form -- that's an element on the periodic table. Does chlorine by itself emit a smell? Or does that chlorine smell in the air probably because the chlorine is reacting with something else?

A: Great question. So chlorine by itself has a strong smell. It's dangerous, as I said. But from our perspective, one of the good things is that we can smell it at much lower concentrations than those that'll hurt us. So 10 parts per million is considered immediately dangerous. Two hundred parts per million would be fatal for the average person over a half an hour. We can smell it around one part per million. Some of us, even at lower concentrations.

So again, if you go to a public pool, you'll smell chlorine. You may even smell it strongly enough that it's making your eyes water, but that's its concentrations well below the kind that'll do you harm. So yes, we do smell it when it comes to these pool tablets, though. The reason we smell those is that they are coming in contact with moisture in the air. They don't have a smell themselves, but they're reacting with moisture, and they are making small amounts of chlorine, and that's what we're smelling, and that's what's irritating our eyes and our nose.