Why Do Car Seats Expire?

CARS.COM — If a baby is on the way, the prospect of shelling out cash — in some cases hundreds of dollars — for a new car seat can be daunting, and a free hand-me-down might sound appealing. But watch out: That seat could have a checkered past, or it could be expired.

Related: Which Cars Fit Three Car Seats?

Why do car seats have expiration dates? How safe are hand-me-downs, and when should you get a new one? We reached out to a range of experts. Here's what we found.

Why Do Car Seats Expire? Is It Just to Help Manufacturers Sell More Seats?

No, it's for good reason. Older seats could have missing parts or owner's manuals. They might also fail to meet current government safety standards, the National Highway Traffic Safety Administration warned in an email to Cars.com.

Lorrie Walker, a technical advisor and training manager at Safe Kids Worldwide, notes that car seats are getting safer all the time through materials and design. Get a used seat, and you'll miss out on that.

"The technology changes over time, especially in this field — we have such great computer models now, and people learn new things about car seats every day," Walker said. "They've done so much more work on the product, and they know that they now have a stronger plastic or a stronger titanium."

Technical standards can change, too. Joseph Colella, owner of Maryland-based Traffic Safety Projects, called that the primary reason for expiration dates.

"The discussion began, for instance, when rear-facing kids were being killed by airbags and the long-required warning label was new," Colella wrote in an email. "By adding expiration dates, manufacturers were preparing for future changes."

Even if you don't care about the latest and greatest safety advancements, a used car seat has been through a lot. Merely normal usage can add wear and tear that can degrade safety. NHTSA cited possible deteriorations in the seat's plastic shell, among other parts. And Sarah Tilton, a child safety advocacy manager at Britax, warned that degradation is especially possible in extreme temperatures.

But I Store My Seat Inside. The Temperature Isn't That Extreme.

Sure, but consider the temperature variations when the seat was in your car. Cars.com Assistant Managing Editor Jennifer Geiger, a certified child safety seat technician, warned that a vehicle interior can "weather years of both hot and cold temperatures, and this constant stress can break down a car seat's plastic shell and degrade other components over time."

What's more, temperature swings are just one aspect of car-seat aging, Walker said. Over the course of six or eight years, sheer momentum can take its toll.

"You may have stopped suddenly 50 times over the course of that eight years," Walker said. "Each time you do that, the webbing stretches a little bit. And is it going to break? Probably not. ... But would you really want to take that chance?"

Added Geiger: "Car seats are also subjected to the forces of everyday use. Each time it's used, the car seat's harness and the Latch connector webbing straps are tugged and have to manage the strain of that constant force."

How Long Is It Before Car Seats Expire?

Experts called six years a typical span, though some seats have a shelf life of up to 10 years. Tilton warned that the clock starts the day they were built, not the day you bought them, so be sure to check the date of manufacture label on the side or bottom of the seat.

"When the process began, virtually all [manufacturers] claimed a shelf life of five to seven years," Colella wrote. "Participating manufacturers agreed that six years was a reasonable timeframe for that, while NHTSA had previously recommended not using a seat that was more than 10 years old. In very recent years, we have watched expiration dates get longer and longer."

Who Sets These Expiration Dates?

Car-seat manufacturers set expiration dates. Lawmakers regulate safety standards for car seats but not expiration dates.

If the Seat Hasn't Been in an Accident or Expired, Are There Risks for Accepting a Hand-Me-Down?

Russ Rader, a spokesman for the Insurance Institute for Highway Safety, warned that used seats could have lurking recalls or a crash history you don't know about. Tilton, meanwhile, advised that you ensure the seat is from someone you trust who can give an honest account of its history and any possible damage.

"Many used car seats are still safe — and can be sold or loaned out safely," she wrote. And avoid any seat that lacks parts or paperwork or that has ever been in an accident, expired or been recalled.

You can check for car-seat recalls online through NHTSA, but Rader cautioned that manufacturers can still recall seats because of failures in the transportation of kids to and from the car, like a faulty handle on an infant seat. You can check for those recalls through the U.S. Consumer Product Safety Commission, Rader wrote.

"It's always best to purchase a new seat," Rader wrote. "If you must use a preowned seat, make sure it has a manufacturer label so you can check for recalls. Don't use a seat with cracked plastic or missing parts."

NHTSA advises that it's OK to accept a used car seat if it follows its safety checklist: the seat has all its parts, labels and instruction manuals, and it hasn't been recalled or in a moderate-to-severe crash.

"If you know and trust the family giving you the car seat, then the risks are low because they can confirm the crash-free history of the seat," Geiger wrote. "If you don't know the family very well or are purchasing the car seat second hand from a thrift store or garage sale, the risks are higher because there are more unknown factors."

It's important to re-register your seat with NHTSA if you get it secondhand, she added. Otherwise you may not hear about subsequent recalls.

If You're in an Accident, When Should You Get a New Car Seat?

Britax's Tilton recommends that you get a new seat if the old one has been in a moderate or severe crash. "Even if the seat looks undamaged, crash forces could have stressed the components in ways that aren't visible, thereby reducing its ability to protect a child in the future," she wrote in an email. "Continuing to use a seat after a minor crash should be fine, as long as you check thoroughly to determine that the seat did not sustain any damage."

Still, Rader noted there's often no reason to replace a car seat after even a moderate crash unless a careful inspection reveals damage — cracked plastic, bent metal parts or stretched harnesses. Fraying straps are another warning sign, Geiger cautioned.

IIHS subjected car seats to successive high-speed crashes and "most of the restraints kept their structural integrity despite minor damage," Rader noted, pointing to a test in 1999 where the Insurance Corporation of British Columbia subjected a range of car seats — including some that were up to 5 years old — to 50 consecutive low-speed crash tests. The seats showed no damage even after an X-ray analysis, and ICBC even found most car seats "unlikely to be damaged in impacts at 30 mph or even subsequent crashes at 40 mph," IIHS said in 2000.

NHTSA added that you don't need to replace seats after a minor crash if the car remained drivable, the door nearest the car seat was undamaged, no passengers were injured, no airbags deployed and no visible damage occurred to the seat itself. If even one of those conditions aren't met, however, NHTSA says you may have to replace the seat.

Replacement seats need not be expensive. Some car seats cost less than $100, and seats sold in the U.S. must meet minimum safety requirements regardless of price. Walker said she's seen no evidence to suggest cheaper seats are unsafe.

"Sometimes you can get a car seat for $60 — a nice one, a good one," she said. "Sometimes the more expensive seats are prettier or they have additional safety built into them, but we don't see an increasing number of children who die in cheap seats versus expensive seats. We don't see any correlation."

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