If your filament is wet (means there is humidity inside the plastic, not that it got dunked but it absorbed the air humidity). You can dry it by heating it to a temperature that is lower than the temp that would soften the plastic. You can use a filament dryer or food dehydrator. Do. Not use. Your. Oven!!! (Ovens don’t have temperature management precise enough and will melt your plastic spool)
To keep your already dried filament, you can keep it in a sealed box with desiccants.
Ha! The oven?! 😬. Hope that's not a personal learning experience!
I keep mine in bags with dessicants in a cupboard in the basement very close to a dehumidifier. Haven't had any issues but have been thinking about buying one of these for the cupboard as well: Arm & Hammer Essentials Disposable Moisture absorber https://a.co/d/3b3d4cP
Curious what people here think - is that just a waste of money (they last 60d)?
All this is good to keep an already dry filament from getting moist.
To dry a humid filament, you need heat and air flow to clear the moist air away. Only an active dehydrator can do that.