If your masks are beginning to feel as old as this pandemic, it’s probably time to get yourself some new ones.

The Centers for Disease Control and Prevention advises using masks that have at least two layers of tightly woven, washable, breathable fabric, such as cotton. When you wash your masks regularly, which you’re supposed to do, the fabric, as well as the fit, can begin to deteriorate. As this happens, your masks become less effective.

“A newer, fresher mask is likely to have tighter fibers, and so it’s likely better at keeping out other particles and keeping your particles in,” says Krys Johnson, an epidemiologist and assistant professor at Temple University.

The exact timeline of when you need to replace a mask depends on the makeup of the mask, along with other factors like how much you’re washing it and how often you’re taking it on and off.

But as a general rule of thumb: “Think about masks like seasonal attire. Update every season,” says Johnson.

Here’s how else to know if you should replace a mask.

It's time to replace your mask if it's loose.
Cynthia Greer
It's time to replace your mask if it's loose.

1. If it’s loose

A snug fit is key. If the elastic of your ear loops starts to loosen, it’s time to reach for something tighter.

It's time to replace your mask if you can see through the fabric.
Cynthia Greer
It's time to replace your mask if you can see through the fabric.

2. If you can see through the fabric when you hold your mask up to the light

That’s a bad sign, says Johnson, and may indicate that the fabric is deteriorating or was too thin from the start.

It's time to replace your mask if you have to keep adjusting it.
Cynthia Greer
It's time to replace your mask if you have to keep adjusting it.

3. If you have to keep adjusting it

A mask needs to cover your nose and mouth in order to work. If one of the straps falls off and you have to keep touching your mask to keep it in place, this defeats its purpose.

It's time to replace your mask if there are any holes or tears.
Cynthia Greer
It's time to replace your mask if there are any holes or tears.

4. If it’s ripped (even a little)

This is perhaps the most obvious sign of all. If your mask is ripped, it needs to go. It doesn’t matter how small or large the hole is.

It might be time to replace your masks so you have more backups for the winter.
Cynthia Greer
It might be time to replace your masks so you have more backups for the winter.

5. If you only have one mask for the winter

Experts strongly recommend owning more than one mask. And in the winter, you’ll want to carry a backup. Moving from chilly outdoor environments into cozy indoor settings makes it easy to sweat through your mask, as does wearing multiple layers. You’re advised to always swap a wet mask for a dry one. A wet mask can make it harder to breathe. And of course it’s uncomfortable, especially if you’re walking back outside into cold temps.

When in doubt, replace it, says Johnson. We want to eliminate risk as much as possible right now, and proper mask wearing is part of that.

It's time to replace your mask if it's disposable.
Cynthia Greer
It's time to replace your mask if it's disposable.

6. If it’s disposable.

If you have a disposable mask, the CDC advises throwing it away after you’ve worn it once.