Locking your doors won’t help when it comes to the latest item that thieves want from your car or truck.

Across the country and into Canada, the trend is to steal catalytic converters by cutting them out from beneath vehicles.

On the scrap market, each converter is worth anywhere from $5 to $100, according to Pat Murphy of Maine Metal Recycling Inc. of Auburn.

“It’s been all over the country,” Murphy said. “Converters are probably one of the single fastest ways to make money right now.”

Just this month, at least 10 have been stolen from vehicles in the Bangor area, including two from trucks in an Eastern Maine Medical Center parking lot.

“They’re not reusing them,” Mike Silver, owner of Silver’s Auto Parts in Orono, said Tuesday. “There’s only certain places that buy these.”

What makes catalytic converters so valuable?

The parts contain a trio of metals – platinum, rhodium, and palladium – that have a relatively high scrap value.

The year, make, and model of the vehicle determine the value of the converter, which is graded as an individual unit.

The majority of the converters that are stolen usually end up being sold from the back of a truck for cash, eventually making their way out of state.

“Those people aren’t selling to people like myself, I would say, most of the time,” Murphy said.

The targets are mostly trucks and sport utility vehicles that are high enough off the ground that the thieves don’t have to jack up the vehicle to get at the part. Foreign models are worth more than domestic.

The parts are made of a stainless steel or ceramic container installed in the exhaust line of a vehicle. Converters have a honeycomb structure consisting of hundreds of channels that are coated with a combination of platinum, rhodium and palladium-based catalysts.

As a vehicle’s exhaust passes through a converter, it changes hydrocarbons, carbon monoxide and nitrogen oxides into water, nitrogen and carbon dioxide, reducing harmful emissions.

Catalytic converters have been required by law on every motor vehicle operated in the United States since 1975.

Unless you catch a thief with ankles sticking out from under your bumper, you might notice a loud rumble when starting a vehicle if the catalytic converter is missing. Replacing the part can cost anywhere from a couple of hundred dollars to a couple of thousand dollars.

“When someone removes it, it would sound like your car has no muffler,” Murphy said.

Unlike a CD player or loose change, a car’s catalytic converter isn’t something you can lock up.

“It’s like someone stealing your tire off your car,” Murphy said.

Although a car alarm probably would be set off by someone trying to remove the part, it’s not a sure thing.

“You could get one off a car in under a minute,” Murphy said. “If you had a person that knew what they were doing and had the right tools, in a night, if they were uninterrupted and hit a used-car lot, in a night they could get thousands of dollars’ [worth of converters].”

A handful of companies in the country recycle converters by crushing, then melting them, or simply melting and separating the different metals the parts contain.

“Most converters are not bought at recycling places,” Murphy said. “Most converter business is done out of the back of pickup trucks. The problem with the converter business is that anyone can do it.”

Plenty of legitimate businesses, such as junkyards and small-engine shops that get the parts when cars are scrapped, handle catalytic converters.

“A lot of catalytic converters aren’t stolen,” Murphy said.

The thefts also are known as primarily a pickup truck business because the majority of licensed recycling and scrap facilities in the state require anyone wanting to do business with them to have an account, which means leaving a documented trail: name, address and phone number.

“Anyone who does business with us has their name in our database,” Murphy said. “Any big scrap guys are going to have that. We operate computers, not a bag of cash in the front seat of a pickup.”

It’s also illegal in Maine to reuse or resell a converter. They have to be recycled.

The largest source of platinum is from recycled converters. The metal then can be turned into a variety of items such as rings and computer parts. It also is used in the medical field.

As with all metals, the demand and scrap value have increased in the last year, boosting the motive to steal.

“What’s good for us is to get these people out of the system,” Murphy said. A family-owned business, Maine Metal Recycling has worked with the Lewiston and Auburn police departments in nabbing area thieves.

“Until there’s some process to control them – that they have to go through licensed dealers – we’re going to have this problem,” Murphy said.