Washington D.C: The International Space Station (ISS) crew members have narrowed down the search zone for an air leak that was recently isolated to the Russian part of the station.

They have isolated the leak location to the transfer chamber in the Zvezda Service Module, according to latest information from Russian space agency Roscosmos.

Additional leak detection operations are being carried out using an ultrasonic leak detector. Roscosmos said that the situation poses no danger to crew’s life and health.

The Zvezda Service Module, the first fully Russian contribution to the ISS, served as the early cornerstone for the first human habitation of the station.

In terms of design, it consists of four sections, three of them pressurised (transfer compartment, working compartment and transfer chamber), as well as the unpressurised assembly compartment housing the integrated propulsion unit.

“The leak, which has been investigated for several weeks, poses no immediate danger to the crew at the current leak rate and only a slight deviation to the crew’s schedule,” NASA said in a blog post on Wednesday.

The space station is actually not designed to be airtight. The orbiting laboratory’s atmosphere is maintained at pressure comfortable for the crew members, and a tiny bit of that air leaks over time, requiring routine repressurisation from nitrogen tanks delivered on cargo resupply missions.

In September last year, NASA and its international partners first saw indications of a slight increase above the standard cabin air leak rate. Due to routine station operations like spacewalks and spacecraft arrivals and departures, it took time to gather enough data to characterise those measurements.

Late Monday night, the Expedition 63 crew was awakened by flight controllers to continue troubleshooting the air leak on the space station that appeared to grow in size.

Meanwhile, the crew was preparing for Sunday’s scheduled space delivery of over 3,600 kgs of supplies and gear aboard Northrop Grumman’s Cygnus space freighter.