Hydraulic fittings incorporating O-rings were introduced decades ago to wage war on the battle against leaks. They have lived up to the task, but because O-rings provide such a simple solution, many designers and technicians take them for granted and may even ignore common sense when using O-ring fittings.

Consider a hydraulic fitting with a Buna-N O-ring that has been stored in a parts bin for who knows how long—probably years. As is often the case, it’s no longer sealed in its original plastic bag. Now, what if that storage bin is in an outdoor tool shed in Florida, where the average humidity in July can reach 80%?

Under the proper conditions a Buna-N O-ring has a shelf life of 15 years—again, under proper conditions. One of those conditions is the humidity must be less than 75%. You can pretty much bet the fitting in question has been exposed to frequent humidity. Pull it out of the bin, put it into service, and you may be asking for trouble—leaks, damage to equipment, or worse.

Read more: Your Connection is Only as Good as its O-ring