At some point in the near future I'll be playing in a slightly modified Slumbering Tsar campaign. The DM has warned us about a potential danger ahead of time because: First, we will be warned about it IC before the adventure begins; and two, without proper preparation it would basically lead to a TPK.
Unfortunately, to really get advice I have to give some detail, so please read and offer advice only if you won't likely be playing in this campaign
at some future point (or, well, if you don't care and can avoid metagaming):
With that in mind, what sorts of spells\mundane items\magical items could people suggest to avoid a painful, suffocating death?
We're probably going to look into the Filter Hood, which he's already said will grant us the +2 to our saves versus the effect.
Thus far I haven't found any magical items we can really afford at our level (7th) that would immediately help. I suppose since we'll have a caster that a wand of Resilient Sphere might do it?
Taking the spell Web Shelter would do the trick, and it's only a level 2 spell that shows up on every spell list except inquisitor, magus, and paladin. Mundane wise, goggles on the eyes to stop blindness, a wet cloth over the mouth and nose does the trick (in a pinch you could just pee on a rag, if it worked against chlorine gas attacks in WW1, it will work against some pesky sand). I'd suggest the former if you can afford to wait it out, but in case you run out of spells or just get caught at a bad time, the having a back up is always good.
Web Shelter probably would not work as a solution; the event deals some amount of damage each round, and I'd guess that's probably to physical objects also; the webbing probably wouldn't survive it.
Tiny Hut would be a valid option, but the wand is a bit pricey; scrolls might be more viable. I know Rope Trick won't work, because the DM told us as much.
A simple tarp could possibly work; I'll check with the DM. Thanks for all the input so far!