Metro trains will be single-tracking on the Red Line between Dupont Circle and Van Ness stations starting Saturday through Aug. 29. Crews will be working on the tunnel ventilation system on the stretch in Northwest D.C., which will help filter out smoke in the event of a fire.

Carol Glover died from smoke inhalation and dozens were sickened during a 2015 smoke incident at L’Enfant Plaza where fans didn’t work properly. The National Transportation Safety Board mandated that Metro upgrade tunnel ventilation systems after the event. The Red Line ventilation shafts and fans were installed prior to modern fire-safety standards for transit systems.

This summer, crews will prepare the areas next to Woodley Park and Cleveland Park stations for new, more powerful ventilation fans. Installation of the fans, testing, and commissioning will follow, and Metro says the new systems will be online by next year.

Trains will single-track between Dupont Circle and Van Ness stations which means trains will only come every 18 minutes along the entire Red Line. Trains will operate more frequently on the east side of the Red Line, coming every 9 minutes until 7 p.m. between Glenmont and Farragut North.

Both stations will be closed on two upcoming weekends — Aug. 7-8 and Aug. 28-29. Free shuttle buses will replace trains. Riders can also use the L2 bus along Connecticut Avenue between Chevy Chase Circle and Farragut Square as an alternative.

The work comes as more workers return to the office, though many are expected to return after Labor Day when the work is complete, according to surveys of larger employers.

But more work is also scheduled for other portions of the Red Line after Labor Day. Starting in September, the Red Line will end at Twinbrook as Metro works on replacing the platform and canopy at the Rockville station. WMATA says the original concrete beam structures, built in the early 1980s, are deteriorating and need to be replaced.

The project will run from Sept. 11 to Dec. 4 and require closing the Rockville and Shady Grove stations. Free shuttle bus service will run among the closed stations to Twinbrook. MARC and Amtrak services at Rockville won’t be disrupted.

Metro will use the closure to make upgrades made at a dozen other stations so far: new lighting, passenger information screens, upgraded speaker systems for announcements, and more.