As a part of hosting, I take it upon myself to do a quick walk-through every couple days. I've been doing this since day one. First, I check that they're not home (car isn't in garage or driveway), and then I knock on the door, and then I let myself in when I verify that they're not present.
I take a quick look around, make sure the trash can isn't full, tissues are stocked, and then inspect to verify that towels are in their proper locations (the bathroom, and not hanging in the bedroom), food is not being stored or disposed of in the rooms, and that they are taking good care of my personal property. (Those are all things that they agreed to in the rules.)
I just had a long term guest leave a week early. She requested a refund of her unused days via the resolution center. Her reason was listed as "uncomfortable" with the host entering the room without permission.
Airbnb reached out to me, and I confirmed that yes, I access my guests rooms without their consent or even notice. Their response said:
"I do truly understand that you would just like to protect your home from damages, and I get that with guests in the past, this has become your primary goal. However, like I said, this is absolutely not something you are allowed to do on our platform. If a guest books your listing as a "private room" they are not expected to share their living quarters, which means this is only for the guest that had booked. By going into this guests listing without her permission, this makes for an uncomfortable and potentially inappropriate situation between you and your guest, and this is something we always would like to avoid."
"With that being said, per our Terms of Service, Section 9 paragraph 5 & 6, I will be proceeding with refunding your guest for the nights she did not stay in your listing. This will amount to a total of $[xxx]. At this time, because you have already received this payout you will be seeing an adjustment to your account for this total. This adjustment will be due to come out of your future payouts."
Nowhere in my reading of the Terms of Service does it say that a Private Room is not accessible to the Host. I've challenged the Manager, but haven't gotten a response back yet.