Ventilation keeps the air pure on board
ABOARD THE USS JOHN S. McCAIN — Say “air lock,” and many people may think outer space — real “Star Wars” stuff.
But to sailors on ships like the USS John S. McCain, “air lock” could mean keeping chemical and biological weapons out of their ship’s insides — and their own lungs.
The Arleigh Burke-class destroyer, with several other classes of ships, has a built-in collection protection system, or CPS. It keeps interior spaces self-contained, using pressurization to seal them from areas contaminated by CBR — chemical, biological or radiological weapons.
Three types of air locks are involved, said Petty Officer 1st Class Christopher Langteau, a damage controlman:
• Type 1: Takes sailors from the ship’s outside portion, known as a “weather deck,” to a “total-protection” area. “Total protection,” Langteau said, means the air is filtered constantly and no CBR threats can get in.• Type 2: Directs sailors from total to limited-protection areas. These are spaces that can’t offer total CBR protection because more air may be needed for operations.• Type 3: These connect total-protection areas to conditional-protection areas, places in which a totally secure environment may be neither needed nor practical.
Langteau said CPS was designed to over-pressurize spaces on the ship, which will force out air if an air lock seal is broken. In the air lock, one can feel pressure building, similar to being in a pressurized airplane cabin.
“You can mess up people’s eardrums,” Langteau said.
Before walking into an air lock, a sailor is to make sure the other side is closed by peeking through a small window. The sailor opens the hatch on his side, walks in, closes the hatch behind him and opens the next hatch.
Lt. Stacey Yopp, the ship’s chief engineer, demonstrated what happens if two hatches are opened at once.
With the interior hatch open, he also started to unleash the one behind him. A considerable amount of air could be heard sweeping past the door.
“It’s difficult to open, but you can,” he said.
But as the second, exterior door opened, a rush of air blew through the space ahead, through the air lock and out into the exterior passageway behind Yopp. It was so strong it blew a box of earplugs off a connection box on the wall.
Yopp said this ensures that possibly contaminated air from unprotected areas is kept from clean spaces.
As soon as Yopp closed the hatch, the CPS’ fans began building the interior pressure back up.
“It’s going to try to keep up,” Langteau said, but “when it has to do that, it’s going to wear out parts quicker.”
He said the crew mostly does “a good job” of not breaking boundaries and forcing the CPS into overdrive to keep pace — “until they get in a hurry. If they have to get somewhere quick … they aren’t thinking.”
Even in port, CPS is in use: It drives about 80 percent of the ship’s ventilation. If it was turned off — if the McCain went to what Langteau called an “open ship” mode — the vessel would have very little air circulation.
One drawback to the system, Yopp said: The air locks can accommodate just a few people at a time. Trying to move large groups from one area to the next can create a logjam.
Crew members say the learning curve for dealing with CPS is pretty short. “It’s not that hard,” said Petty Officer 2nd Class Michael Reinhardt. “It’s a pretty basic system.”
“It’s easy to remember it’s there,” Langteau said, “because you always hear the air.”