Hi Freyashamsters. You will need to block that off so that air won't be going through. I noticed that my hammies immediately go to an opening, like the water bottle opening, if it isn't blocked.I think they might feel a draft from there and go to check it out.
Hamsters most definitely can chew at heavy plastic and once they start it's a pain to get them to stop. They remember and will try to move things out of the way just to get back at that spot. So, you want to address the problem before hammy has decided it's a favorite place to be.
We have had quite a lot of hammies chew holes in their homes and escape. The stories are in lots of threads. Some hammies are such determined little chewers that they wind up only being able to be house in tanks. Kyrilliondaemon's Eggbiscuit (Nicknamed Chainsaw Jaws), especially comes to my mind. That hammy was the Olympian of chewers!
When that little ham went on to the Rainbow Bridge, Krill posted a memorial that described her to a T. Be prepared!
Boo Bumbleham and Eggbiscuit Screecha