Members of the Atlantis crew work in the space station's Unity docking node. Photos: NASA

Work to improve air circulation aboard the international space station has apparently paid off with low carbon dioxide readings and no reports of any adverse health effects from the crew of space shuttle Atlantis. During the most recent previous space station visit in May 1999, astronauts reported stale air in parts of the station and symptoms of high carbon dioxide concentrations. This time around, the Atlantis astronauts employed a different ducting scheme to more thoroughly scrub the station's air through the shuttle's filtration system and to ensure good mixing back in the station.

The space station currently is made up of two large modules: The Russian Zarya propulsion module and NASA's Unity node, a multi-hatch module that will serve as a gateway to future station components. The two modules are connected by a short tunnel called a pressurized mating adapter, or PMA. Another such PMA connects the shuttle to the node. The goal was to ensure that air in the Zarya module, which is farthest from the shuttle, is forced into the orbiter's filtration system.

"We did make some changes to how we routed some of the ducting so that we improved air exchange between the FGB (Russian Zarya module) and the node and the orbiter where all the air scrubbing is done," said station flight director Paul Hill. "We've done a lot of work to make sure we have improved what air scrubbing, or air exchange, we're doing with the station to make sure we don't have any stale air back there. We've also provided a number of portable fans the crew can set up at whatever work site their in. (But) we have had no reports (of bad air quality)."

Shuttle flight director Phil Engelauf agreed, saying "we haven't seen any indications of adverse effects or poor air quality and with the conditions we think we've created with these ducting mods, we're optimistic we'll keep the air as good as we can possibly make it in the station."

When the astronauts entered the space station shortly after 8 p.m. Monday, temperatures in the Zarya module were around 75 degrees. It was a much warmer 86 degrees in the Unity node, hot enough to prompt astronaut Jeffrey Williams to doff his shirt. But Hill said that was an expected, short-term effect and no problem for the crew.

A high-resolution view of Jim Voss during Sunday night's spacewalk outside the station. Photo: NASA

"It was a little bit warm in the node, the crew was getting a little bit hot," he said. "That's not necessarily unexpected. We hadn't established ventilation or air exchange with either the shuttle or the FGB right away (and) we spent several days warming up the shell to prevent condensation.

"So it did start out a little warm in there," he said. "The node is already cooling down to a more comfortable temperature level. Now that we're inside and we know we have the shell warmed up, we've also dropped some of our heater power to make sure we keep it at a more comfortable level for them. From every other perspective, the station looked good inside."

By 3:15 a.m., the astronauts had changed out one of Zarya's ailing batteries and were wrapping up replacement of a second. They also replaced two charge-discharge units and one battery controller. The work went much faster than expected with no problems of any significance.

"The day started off very well," Engelauf said. "The crew was aggressive and got a little bit of a head start on the ingress activities this morning. We worked our way through the PMA and into the node and all the way on into the FGB well ahead of the timeline for the day and the crew was able to get through all the ducting reconfigurations, take all the air samples and go ahead and get started on the electrical power system component changeouts well ahead of the schedule.

"We made up roughly about an hour on the timeline," he said. "Everything went perfectly today. All the scheduled activities were completed, there were no particular problems. ... The crew's well ahead of schedule and we're making good progress."

Said Hill: "Everything's going as planned, it couldn't be going better for us."

You can follow the flight of Atlantis in Spaceflight Now's Mission Status Center. We will provide continuous play-by-play reports throughout the entire 10-day shuttle flight.