For small hotels with fixed glass windows(permanently closed window) how do you get rid of the odor before the next guest checks in in a few hours?

Noticed that some guests who live in a room for couple of days end up leaving a weird odor which is extremely noticeable for anyone else who goes in that room. Having a permanently closed windows means you can't get the fresh air in.

Using a room freshner would only mix with the odor but not really remove it.

How do you ensure that the odor is completely gone before the next guest checks in in a few hours?