A decent surge protector is an important piece of equipment in any office or entertainment centre. They don't last forever, though, so make sure to purge your surge every few years to keep your electronics protected.
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Surge protectors work by absorbing excess voltage into a metal oxide varistor (MOV) so your electronics don't take the hit. The protective MOV degrades based on how much it's absorbed over time, and when it's completely degraded, there's no more protection being provided. As Chris Hoffman at How-To Geek explains, the lifespan for surge protectors is measured in joules:
Every power surge your surge protector absorbs decreases the amount of future joules it absorbs. If that 1000 joule surge protector takes an 1000 joule hit, it's done for. But it's also done for if it takes ten 100 joule hits -- or if it takes a thousand one joule hits. It's all cumulative... It's all about how many joules your surge protector has absorbed. But, the older your surge protector is, the more it's likely degraded.
So how do you know when your surge protector has turned into an unprotected powerboard? Unfortunately, you can't know for sure. Some surge protectors have lights that may warn you when there is no protection, but it can still be risky if it's an old unit even if the light's on.
If it's really old -- like you don't remember when you bought it -- it's probably not protecting you and you should toss it. If you're aware of your surge protector taking a big hit, you should probably toss it too. Otherwise, a good rule of thumb is to replace your surge protectors every two years. To read more, check out the link below.
Why (and When) You Need to Replace Your Surge Protector [How-To Geek]