If a hot and sweaty audience is a sign of a good heavy-metal show, then the bands performing at Station 4 were a little too good in the eyes of St. Paul officials.

The Lowertown rock club abruptly closed last weekend and will remain shuttered all summer, pending an upgrade to its ventilation system mandated by the city. Its owners hope to reopen right after Labor Day.

Steve Ledin, co-owner of Station 4, said the building’s owner had been in negotiations with the city for more than a year — and up until last week — hoping to keep the club open while the new ventilation was built. The upgrades proved more costly than expected, given the structure’s century-old construction — about $100,000, which required Alan Peterson, owner of the building and co-owner of the club, to refinance the property.

With a deadline set for last Friday, the city pulled the club’s certificate of occupancy. The club threw a “last-minute metal party” on Thursday night featuring Deretla Thrash, Plagued Insanity and other local bands that could have trouble finding gigs elsewhere.

“The city ran out [of] patience, apparently,” said Ledin, who did not deny that the venue could use the new air system. “When Hollywood Undead or some other band is playing here to 500 excited metal fans, yeah, it can get pretty stuffy.”

The club, on the corner of 4th and Sibley streets across from Union Depot, has been a haven for metal and punk bands going back to the 1980s and its previous incarnations as Ryan’s and the Lab. Over the past two years, Ledin said, the club saw about a $1 million decrease in revenue that he attributes mostly to light-rail construction.

Still, Station 4 soldiered on with its dedicated metal base. Among the concerts on the club’s calendar were about 10 shows by national touring artists. Those will be refunded or moved to other venues. Tuesday’s Intronaut gig quickly found a home at the Garage in Burnsville, while the Summer Slaughter Tour with Dillinger Escape Plan on Aug. 14 landed at the Cabooze.

On the upside, Ledin said the refinancing will permit other refurbishments to be made.

“It would have been nice to not have to cancel the [60-some] shows we had booked for the summer,” he said, “but we’ll get the chance to make it up to everyone once we reopen and improve on the place.”