5 things around the house and car you probably didn't know expire

PHILADELPHIA (WPVI) -- Milk, medicine, your car registration, we all know those things expire.

But a closer look around your house and car will reveal that many potentially lifesaving items also have expiration dates.

Some expiration dates are easy to spot, such as those for items in your refrigerator and medicine cabinet. But others are not. For example, smoke alarms help protect you and your family but only for about 10 years. The sensors can degrade over time, so you should look at the manufacturer or expiration date to know when to replace them.

The same goes for fire extinguishers. They last about 12 years because they can lose pressure. Also, they might have broken or missing parts and corrosion. After it expires, you can't throw an extinguisher in the trash. You should check with your local fire department, recycling center, or hazardous-waste disposal facility for guidance.

You may be tempted to reuse a car seat or buy one used, but keep in mind they're only good for six to 10 years to ensure that seats on the market are current with the latest safety features and standards.

The materials they're made of degrade over time, which could make them less safe. And if yours is expired, check online for trade-in programs or see if your local recycling center will accept it.

Just like car seats, the components that makeup bike helmets can degrade over time. CR's experts recommend that you replace your bike helmet every five years. And CR reminds us that any bike helmet that's in a crash should be replaced and that any car seat that's in a moderate or severe crash also needs to be replaced. You can check NHTSA.gov for details.

If you like to stock up on sunscreenwhen it's on sale, you've got about three years to use it. After that, sunscreen starts to lose its sun protection powers. But the good news is that an open bottle of sunscreen doesn't expire any faster than one that is unopened.