Studied biochem long ago, haven't worked at that field. I understand some but no expert.. feel free to correct/challange me:)
(1) Exposure to air looks fine, you've seen that thread:
https://sanctioned-suicide.net/threads/testing-sn-would-require-exposing-it-to-air.28664/
* All reactions described in literature are for 300C, or under pressure, or with other reactants (with sulfur bacteria etc). Lack of any other well described reaction time -- indicates degradation in room temperature is slow (weeks if not months).
(2) Also some moisture and air is ok:
https://sanctioned-suicide.net/thre...-hard-and-clumpy-should-i-still-use-it.26451/
* Clumps are normal. Research says "rate of oxidation related to surface", that is don't 'spread it around'. Actually clumps may be good (less surface to interact with air).
(3) Sodium nitrite is produced by reduction of nitr
ate salts - exposure to heat, light, etc. That is, heating nitr
ate results in SN+oxygen. Safe to assume that's the rather stable result. We know it can be further be reduced to other harmful substances, if conditions are right, I don't think just O2 at room temperature and pressure would do that in few hours.
NaNO3 -> NaNO2 + O2
As for the specific question, air tight container after exposure should be fine, I agree with what you wrote -
- - - - - - - -
I think we may overthink the entire thing, and worry about every iota of SN (while 10g in intestines is enough). I understand why, we're anxious and wary.