HOUSTON -- Picture returning home after a long day at work. At the door, your significant other hands you earplugs, an electric fan and carbon dioxide sensors. Oh, and be on guard, the smoke detectors and fire extinguishers may not work.

Working overtime seems a lot more attractive now.

Luckily for us earthbound types this isn't a reality, but it may be for astronauts living and working in the International Space Station (ISS) as NASA tries to correct hazards pointed out in a recent General Accounting Office (GAO) report.

"I'm comfortable we'll resolve those issues satisfactorily or they're already resolved," said ISS project manager Tommy Holloway.

As the crew of Atlantis works in and outside of the ISS, they'll take precautions and make several quick fixes designed to correct some of the problems.

The GAO took issue with several hazards present in the currently orbiting Zarya module, as well as the Zvezda service module to be launched this summer after more than two years of delays.

The congressional watchdog noted both modules' failings:

• Inadequate shielding from orbital debris on the Zvezda
• Inability of either Russian-built module to operate if cabin pressure is lost
• Lack of verification of window design and service life on Zvezda
• Excessive noise levels in Zvezda and the U.S.-built Unity module

Holloway said ISS managers are reviewing the problems and working on solutions to them.

Also highlighted in the report were the strange symptoms reported by the first shuttle supply flight crew to the ISS last spring. Some of the astronauts suffered from headaches, flushed faces and nausea while working in the Zarya module. Crew members attributed the symptoms to poor ventilation and high carbon dioxide levels, but the cause remains a mystery.

"We've studied and analyzed the situation," Holloway said. "We don't have a definitive cause for those particular events."

Shuttle Endeavour docking with the International Space Station

He added engineers doubt the symptoms came from carbon dioxide, but possibly the Russian module being warmer than the U.S. module. Air samples taken on entry and exit of the station showed normal readings - no higher than normal levels of carbon dioxide and contaminants.

Small amounts of carbon dioxide can cause nausea and headaches, while high levels can be fatal. During the ill-fated Apollo 13's aborted flight to the moon in 1970, oxygen supplies weren't an issue, but excessive amounts of carbon dioxide. The three astronauts had to jury-rig lithium hydroxide canisters to scrub the gas from the spacecraft. Similar systems are still used today.

The space agency isn't sure what caused the astronauts' maladies on the first visit to the station and declines to identify which of the seven-person crew got sick, citing medical privacy concerns.

Despite this, the crew of Atlantis seems to be well prepared to ventilate and test for contaminants aboard the two modules of the station already aloft.

Atlantis crew member and future station occupant Susan Helms and others have speculated a reason might be carbon dioxide bubbles that formed near the faces of astronauts.

"In space we don't have the gravity to take the heavier air and pull it down and have lighter air rise to the surface," she said. "I think that some of the theories were that crew members experienced a bubble of carbon dioxide around their faces because, perhaps, they didn't have their head somewhere where they were getting this continual artificial ventilation."

Discovery crew members Rick D. Husband, pilot (left); Tamara Jernigan, mission specialist and Commander Kent V. Rominger in Zarya

As one solution, the astronauts will carry portable fans and place them where the airflow will stir up the currents near their faces.

Before astronauts enter the station, the hatch will be opened and the docked orbiter's environmental system will circulate the air and clean it of any contaminants. The astronauts will also carry portable monitors to warn them of any airborne contamination.

Also on the list of astronaut chores is to improve ducting in the modules to improve airflow, numerous samplings of air quality and constant reporting of conditions to flight surgeons at Johnson Space Center's Mission Control, which the last crew was hesitant to do.

"We want to handle this in an open discussion on what we're feeling and what our instruments are telling us and communicate this to the flight director and flight control team" said mission commander Jim Halsell. "If there are issues, then they can apply all of the engineering skills we have at Johnson Space Center to solve those problems in real time."

Science teachers love to point out the inaccuracy of some science-fiction films where in the deadly silent vacuum of space you hear rocket engines, lasers (as if lasers made noise) and explosions. Inside a spacecraft is another matter entirely.

The void of space may be soundless, but to the occupants of a spacecraft it's a cacophony of pumps, gurgling cooling lines, fans, ventilation ducts and electronic devices to name a few.

The GAO found the Zarya module to be noisier than expected, and the Unity module also isn't a quiet place. When the Russians launch the Zvezda service module this summer, it'll be noisy too.

Cosmonaut Valery I. Tokarev prepares a camera on shuttle Discovery's 1999 mission to the ISS

Specifications call for noise levels not to exceed an average of 55 decibels in a 24-hour period. That falls between the noise of a typical house and a conversation. Currently, the GAO reports noise levels in the 62- to 64-decibel range, a decrease from 65 to 74 decibels before modifications were made on Zarya.

Long-term exposure to noise can cause hearing loss and fatigue -- two things that can be an added hazard in an already precise and dangerous occupation.

U.S. astronauts aboard the Russian space station Mir complained about the noise levels, and at least one suffered a temporary hearing loss. A study conducted of Mir cosmonauts showed some had suffered permanent hearing loss and were disqualified from further space flights.

The soon-to-be launched Russian service module is a close kin to the base block module aboard Mir, but NASA hopes to make some improvements.

"We've got plans to decrease the noise levels in the service module," said Bob Cabana, ISS international operations manager. "We'll see how well design changes reduce the noise level and, in the meantime, we'll provide hearing protection."

The interim solutions considered include noise-canceling headsets, earplugs and turning off unnecessary equipment.

Noise levels vary throughout the station, so astronauts might be able to find a quieter spot, Cabana said.

Fire remains a major hazard inside a spacecraft. You can run from a burning house, but there's nowhere to go in space other than to abandon ship. Aboard the ISS, Atlantis' crew can escape aboard the shuttle. When a permanent crew arrives in the fall, they'll leave via the docked Soyuz and, by 2006, the X 38 Crew Return Vehicle will be available as a lifeboat.

Apollo 1 astronauts Virgil "Gus" Grissom, Edward White and Roger Chaffee died in 1967 during a countdown test when a fire fueled by the pure oxygen atmosphere raged through the capsule. More recently, aboard Mir in 1997, cosmonauts battled a fire in a defective oxygen generator.

While on their 11-day mission, the crew of Atlantis will replace fire extinguishers that have passed their expiration date and replace more than a half dozen smoke detectors that may be defective.

Cabana said engineers weren't sure if the smoke detectors were defective, but were replacing them to be safe.