Back before I switched to paper towels for substrate (so much easier to clean), I would use aspen shavings. One day my BP ingested a good amount during a less the routine feeding. Fortunately for me nothing in his behavior or health changed.

I had him checked out by a vet about a month later (regular check up), and everything seemed fine.

I think what saved me was that aspen shavings are relatively thin, and he pooped it out like usual. Fir bark though, I'm not sure how thick it is.

If you have a vet with experience in herps, I'd call him / her and see what they reccomend.