Houstonians are calling 911 and asking the same question: what are those large spitting and squealing chemical tanks on street corners and could they blow up?
Those canisters are full of nitrogen and are usually set up in the open. Sometimes, they make noises and spew what looks like smoke. The tall tanks on 43rd Street in northwest Houston are a stone's throw from Oak Forest Elementary.
"I think it's dangerous for the kids," an expecting mother said as she was pulling her toddler in a wagon right by the tanks. "I don't think they're safe there."
"It's completely safe," Houston Fire Department Capt. Ruy Lozano said.
Those tanks belong to AT&T. The nitrogen is released underground to keep the phone lines free of moisture.
"The important thing to note is it's an inert, non-flammable material, so it does not pose a threat to the community," Lozano said.
He can understand why Houstonians are calling 911 about them.
"You got to understand: whenever you have one of these bright silver tanks on your local corner and you see a cloud coming off, it's going to be unnerving," he said. "We've done our investigations. We've never had problems with these in the past."
The air we breathe is made up of mostly nitrogen. What most of us know about liquid nitrogen is from middle school. Remember the demonstration in science class when the flower and the hot dog were frozen solid in seconds? That explains one of the warning labels on the tanks: "can cause severe frost bite."
"But that would have to be at a point where maybe you were a technician working with it," Lozano said. "That's why technicians wear gloves."
Many residents are concerned the tanks are too close to the street.
"You know it's on the corner," one concerned citizen said. "Sometimes there are accidents. That can break that thing in pieces."
Lozano said there's no need for concern.
"The tanks are extremely durable stainless steel, but it's actually a tank within a tank," he said. "If a car hits it, it's very difficult to pierce."
If by some chance the tank ends up leaking, he said nitrogen expands so quickly, it goes from a liquid to a gas to completely disappearing in a matter of seconds. There's also a label on the tank warning of "rapid suffocation." That is only a risk in an enclosed area.
By the way, that steam or smoke that sometimes spews from the tank is just a valve releasing perfectly harmless pressure, he said. Here's a statement from AT&T:
"We believe the tanks in questions pose no danger as they contain a non-flammable inert gas (nitrogen) that is used to keep moisture out of underground telephone cables. This is a common, industry-wide practice used for maintaining underground cables. The nitrogen from the tanks keeps moisture out of the underground telephone cables and the telephone lines operating properly".