Desiccant (a moisture absorbing compound), can be a good thing to use if your PCB is at risk for condensation.
Desiccant can be re-used, just by drying it in the oven.
Put in on an oven tray.
Set the temperature to 125°C.
Set the timer to 5 hours.
Be warned though, some packs of desiccant can't handle the heat from re-drying! The packs which exploded/melted in the picture below where all the same brand, and the desiccant packet felt plastically rather than the other that felt more like paper.