When CHS saw this mysterious machine speeding down 12th Ave on Tuesday, CHS thought, “Oh crap, something serious must be happening.” CHS was right. Capitol Hill’s Fire House 25 is home to the city’s only mobile ventilation unit, MVU 1 — a joint purchase between Sound Transit and SFD to bolster Seattle’s tunnel firefighting capabilities. On Tuesday, it was put to good use.

A south Seattle warehouse filled with so much smoke when a food trailer located inside the building caught fire that emergency crews couldn’t clear the building using their standard ventilation equipment, according to Seattle Fire Department spokesperson Dana Vander Houwen. MVU 1 rolled from Fire House 25 to ventilate smoke from the east end of the large warehouse to an opening on the west end.

The unit is a relatively new addition to the city’s emergency arsenal. Sound Transit put a federal grant to use pay for the actual MVU fan unit which prices somewhere between $130,000 and $195,000 depending on features while SFD put its grant money to use to buy the $50,000 truck that carries the unit. SFD is also responsible for maintenance and training but, as we’ll write more about soon, the department has received funds from Sound Transit to train its personnel for tunnel fires and emergencies.

Though MVU 1 is headquartered on Capitol Hill, it was not purchased only for the University Link section of light rail tunneling that will pass under us. The original driver for the unit’s 2006 acquisition was Sound Transit’s plan to begin train service north of Seattle via the Great Northern tunnel which passes below the city. MVU 1 has been periodically deployed but its first big moment in Great Northern usage came and went last month when the tunnel filled with smoke as a commuter train passed through. It turns out, the smoke came from another train’s diesel exhaust, not fire, so MVU 1 never left Pike/Pine.

You can learn more about the technology involved in the MVU 1 from this Federal Emergency Management Agency page and watch one in action here as it clears a recycling plant of smoke during a fire in Illinois.

CHS will have more about MVU 1 and other emergency preparations Seattle has taken as it increases the mileage of underground public transit in the city.