Is it safe to leave toilet flange hole unplugged?

[Bienes Raices]

I put some epoxy on the flange to cover a small crack, and it's still drying, so I didn't want to stuff a rag in the hole and mess up the epoxy. I read that sewer gas can potentially cause an explosion (although this house is on septic and it was pumped out a month ago). Are there any concerns leaving the hole unplugged for one night while the epoxy dries? Thanks.

[Jon Holdman]

Originally posted by Brian Hoyt:

Additionally, there's probably a pea trap down stream that will keep the sewer gasses from the public sewer from coming up.

Below other fixtures, yes. But the toilet, not. The toilet itself contains the trap. Thats the water you see in the toilet after you flush.