A parking garage at San Francisco International Airport. While thefts of catalytic converters have become an all-too-common experience, it’s perhaps unexpectedly uncommon at SFO parking garages, where millions of cars sit idle across the course of a year.

After a vacation full of unexpected calamities — a family member’s heart attack, multiple COVID-19 infections and an isolation period that derailed travel plans — Kelly Connolly and her two young children looked forward to touching down at San Francisco International Airport, retrieving their car from the long-term parking structure and driving home to Milpitas.

But apparently, “the vacation from hell,” as Connolly’s husband put it, was not yet over.

Once the family loaded up their luggage, Connolly attempted to start the car, and it let out a loud screech.

“I knew right away what had happened,” Connolly, 42, said.

Connolly recognized the sound because she had heard it before. In January, someone swiped a catalytic converter from the family’s 2008 Toyota Prius, which was parked in front of their house.

Catalytic converter thefts are common in the Bay Area.

“I was disgusted,” she said. “I was upset, too, thinking about how I’d have to deal with this again. I just wanted to go home.”

Her story may come as a jolt to millions of travelers seeking to stow their cars in airport garages each year, at a time when catalytic converter theft is rising on Bay Area streets and parking lots.

To some degree, SFO has managed to shield itself from the surge.

Data compiled by airport officials shows these thefts are still uncommon at SFO, affecting a small fraction of the 1.54 million vehicles parked in the short-term and long-term structures between January and July. About one in every 13,000 vehicles that sat in the lots during this period was linked to a theft call of any type, according to San Francisco Police Department records shared by the airport’s public information officer, Doug Yakel.

Reports of catalytic converter theft were more scarce, affecting fewer than one in every 77,000 motorists who paid for parking.

Security personnel are on duty around the clock at every parking garage at SFO, where they perform regular patrols of the garages looking for any “suspicious activity or vehicles,” said Yakel, who added that the airport is doubling its security staffing from two officers per shift to four by the end of this month.

In 2022, the airport received 112 calls related to theft in its garages, and 18% of them — 20 calls — were related to catalytic converters. SFPD’s airport division didn’t start breaking out catalytic converters as a separate category until the end of 2021, but in December, 32%, or eight out of 25 calls, were related to catalytic converter thefts at its garages.

Other thefts calls include any car break-ins, theft of the car or any part of it, or theft of contents in the car, according to Yakel.

A vehicle is in place for catalytic converter installation at Johnny Franklin Muffler in Santa Rosa.

Elsewhere in the Bay Area, the issue is much more prevalent. Catalytic converter thefts have skyrocketed across the region and the nation throughout the pandemic,

with some mechanics even calling the crime pattern “the other epidemic.”

Deft thieves have zeroed in on the devices, which are a part of a car’s exhaust system located on its underside that can be sold for up to $300 at a scrap yard or to a recycler.

Precious metals like palladium, platinum and rhodium inside the converters are worth thousands of dollars per ounce, and the relative ease of stealing one has become a major driver of catalytic converter crime. If a thief is well-prepared, a converter can be removed in less than two minutes with only a saw or a wrench.

Hybrid models, like Toyota Priuses made from 2004 to 2009, are prime targets for catalytic converter thefts because the devices are comparatively easy to access. And since hybrids consume less gasoline, the precious metals within the converters are less likely to be corroded. SUVs and trucks that sit higher off the ground also offer more convenient access for thieves and have also become popular targets.

The booming theft and fence operations have made it more costly and time-consuming to replace stolen catalytic converters. Some auto body shops have run out of the product and had to back-order more, due to high demand. As the trend persists, nervous motorists have opted to take a more proactive approach: bolting an aluminum plate over the catalytic converter to cover it, which can cost around $450.

Connolly also considered this expensive, precautionary measure.

On the night of her SFO ordeal, Connolly spent hours dealing with claims and paperwork, then hitched a ride home from a friend, only to return to the airport the next morning to tow the car. In the end, she managed to get her catalytic converter replaced. A parking refund from the airport was on the way, Connolly said.

Still, with two thefts in less than a year, Connolly said she and her husband were pondering whether to splurge on the plate, or try something more drastic: get rid of the car altogether.

“It’s such an old car, and who would have ever thought,” said Connolly, referring to how it’s been targeted for theft over the past year. “In the past, we left our Prius parked in our driveway when we were on vacation. We would never dream of doing that now.”

Annie Vainshtein (she/her) is a San Francisco Chronicle staff writer. Email: avainshtein@sfchronicle.com Twitter: @annievain

Annie is a reporter for The San Francisco Chronicle. She previously was a digital producer for The Chronicle's Datebook section. She graduated from Cal Poly, San Luis Obispo in 2017 with a degree in journalism. During her time there, she spearheaded a culture column, produced radio pieces for NPR-affiliate station KCBX, and was a DJ and writer for KCPR, the campus radio station. Before joining the Chronicle, she was an associate producer at SFGATE and interned at VICE and Flood Magazine. She's particularly interested in communities and scenes that are often misunderstood.