If you see smoke Friday night coming from the under construction Capitol Hill Station, you can probably relax. Sound Transit says contractors will be conducting tests of the station’s “airflow” —

Friday, May 22, from 4:30 p.m. – 10 p.m. Sound Transit’s contractors at both the Capitol Hill and University of Washington Stations will perform airflow tests in the University Link tunnels. Nearby residents and passersby may notice artificial smoke (a dense vapor produced by a fog machine) exiting vent shafts at the station sites. Additional airflow tests will also be performed on May 30-31 and June 6-7 during daytime hours.

If this were an actual emergency, never fear — Capitol Hill’s Fire Station 25 is home to Seattle’s only special tunnel firefighting machine.

The work is part of preparations through the rest of 2015 to open Capitol Hill Station and the U-Link light rail extension connecting downtown to Montlake by way of Broadway.

You can get a sneak peek here of the UW station and a look here at what it’s like inside the 3.1 mile tunnels. Riders will descend around 90 feet via escalators and elevators to reach the Capitol Hill Station platform, according to Sound Transit diagrams. In addition to the main entrance near Broadway and John, the station will also be accessed by an entrance near Denny on the west side of Broadway and a third entrance on the south end of the site. By 2030, about 14,000 Capitol Hill riders are expected to board the light rail trains each day.

Above ground, the process to develop the sites around the Broadway light rail site with a mix of affordable and market-rate apartments, a community plaza, and commercial space — including a home being planned for a new grocery store — is underway and planners are adjusting bus routes in anticipation of the new transit service coming online. Meanwhile, the surface level streetcar has begun testing on Broadway with hopes of opening the service to riders later this summer.