Does solid sodium hydroxide react with carbon dioxide and air moisture?

I heard a claim in the context of soapmaking that a stray grain of sodium hydroxide will decay into soda ash, i.e. sodium carbonate, on contact with air. This reaction happens in [an aqueous solution](https://chemistry.stackexchange.com/questions/64570/would-sodium-carbonate-from-carbon-dioxide-plus-hydroxide-be-formed-in-solution), but I'm wondering how fast it would happen with only the air moisture absorbed by the hydroxide grain.


More to the point, some of the sodium hydroxide grains I have for soapmaking seems to have stuck together into a solid lump by absorbing air moisture inside the closed container. Should I assume a nontrivial fraction of that has turned into sodium carbonate by now?


