Any suspicious sound coming from a vehicle is usually enough to cause drivers concern. So if you turn the key and are greeted with a loud growling roar, you'll know right away that something is wrong.

This unsettling din may indicate that your catalytic converter has been stolen. According to the National Insurance Crime Bureau, the number of catalytic converters reported stolen each year grew from 3,246 in 2008 to 3,986 in 2015. Between 2008 and 2015, at least 25,394 of these components were removed from vehicles; the number is likely much higher, since the figure only reflects insured losses.

The theft of a catalytic converter not only increases the chances of engine damage, but can also be expensive to replace. To avoid this hassle, you can take steps to better secure your vehicle and this component.

Why they're targeted

The catalytic converter is part of your vehicle's exhaust system. According to the Automobile Association, an English organization, catalytic converters use chemical reactions to reduce the severity of the emissions generated by the engine. The device can oxidize materials to produce carbon dioxide and water rather than more harmful substances such as carbon monoxide, while also removing oxygen from some substances such as nitrogen oxides.

To achieve this process, catalytic converters use certain precious metals such as palladium, platinum, or rhodium. The NICB says these metals can garner hundreds of dollars per component when turned in at a recycling center or scrapyard.

Thieves can also remove a catalytic converter from a vehicle within a minute, allowing them to collect several in the course of a day. SUVs and other vehicles with more clearance are targeted more often, since it is easier for a thief to access the undercarriage. Catalytic converters are also frequently stolen from vehicle dealerships, commuter lots, and other areas with a high concentration of vehicles.

The costs involved in a catalytic converter theft may not be limited to replacing the component. Tom Moor, writing for Angie's List, says thieves may not make the neatest cuts when removing the component. In the process, they may damage an oxygen sensor or other parts of your vehicle, leading to higher repair costs.

Catalytic converter theft is fairly rare in this area. According to the NICB, 268 of the components were stolen between 2008 and 2015. In Rhode Island, 46 thefts were reported during this period. By contrast, California had the most catalytic converter thefts at 8,072, with Texas a distant second at 1,705.

Still, common sense steps will help guard your catalytic converter against theft. Some of these actions will also reduce the risk of other malfeasance, such as vehicle break-ins.

Theft prevention

Keep your vehicle in a safe place. The Automobile Association recommends storing it in a garage whenever possible, and parking on a well-lit street or in an area with plenty of foot traffic.

Josh Max, writing for Autoblog, says you can also install a home surveillance system that will record anyone approaching your vehicle. Following the local news will let you know if a rash of catalytic converter thefts has been reported in your neighborhood.

Once a catalytic converter has been stolen, it can be difficult if not impossible to track down. One way to combat this issue is to have your license plate number or vehicle identification number etched onto the component's heat shield. The NICB says dealerships and other local businesses often offer this service, which serves as a deterrent to thieves and can help police track down missing components.

Some vehicle owners decide to attach their catalytic converter to the vehicle more securely. Moor says a mechanic might weld it to the vehicle frame or attach a protective enclosure, such as steel plates or a cage. However, Max says this step can lead to added expense if a mechanic needs to remove the catalytic converter at a later point.

Some aftermarket devices have been marketed to protect catalytic converters, including reinforced straps and alarm systems. Before investing in these devices, make sure they have been tested and that their effectiveness has been confirmed. The NICB says you should also make sure that any modifications intended to protect the catalytic converter will not void your warranty.

Moor says that if you find that your catalytic converter has been stolen, you should report the theft and take the vehicle in for repairs as soon as possible. While you can drive to the shop without the component, you should not forgo the repair and start driving regularly without part of your exhaust system. Doing so can increase the chance of engine damage, particularly if the thief damaged other components, and will also increase the amount of toxic emissions you are putting into the atmosphere.