How to explain my room

just tell people its none of their fucking business.

You could do what I am currently working on. Tape a small fan into each hole in the door then take a cardboard box and staple it to the inside of the door so it is built around the fan. Cut a hole in the box and tape or staple a small carbon filter to the box so the air gets pulled through the filter and pushed out the door so there is no smell and you wont see any light either. On the outside of the door just screw in some metal vents so it would look like its just a vent for your laundry room. No one will even think twice. My setup I'm working on will cost less than $50. The fan I ordered cost $14 and the filters I got are like $5, I got both on amazon. I don't have the metal vent yet, but you can get those fairly cheap too. If you need it explained better message me and I'll give you as much detail as you need.

put a lock on the door and tell people that it is a storage room that belongs to the landlord.

I had an invisible roommate once. He happened to never be home. Always locked his door.