I have bought some damp traps. When it comes to refilling them, what substance would soak up the most moisture? Googling, dishwasher salt and cat litter have been suggested, but nobody seems to be able to say exactly what would, in principle, absorb the most moisture.

  • 2
    I neither know nor care what they put in those things, but in a long-term cost-effectiveness sense you want a material you can regenerate (dry, generally with oven heat), not discard - or you want a dehumidifier (refrigeration/electrical type) - those things are a cash cow for the makers of the filling no matter what you put in them. Your sources are dubious if they think that cat litter pulls water from the air.
    – Ecnerwal
    Jan 19, 2018 at 16:40

2 Answers 2


Calcium Chloride.

They sell it as driveway ice-melt by the 5 or 10 pound bag so it is cheap. It is even used in pickling to make vegetables crisp.

It makes a great desiccant.

  • Yes, calcium chloride is the answer. The Safety Data Sheet for the DampRid refill says that's what is mostly in there too: Calcium chloride 60.0 -100.0 %, Sodium chloride 1.0 -5.0 %, Potassium chloride 1.0 -5.0 %
    – Dotes
    Jan 19, 2018 at 22:05

I'd wager that the granules they sell to refill the damp traps are going to absorb the most moisture of any commercially available product. If there was something that worked better, they would fill the damp traps with that instead.

Example: DampRid Refill

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