Properly close the door and cover the sides with something like a towel or bedcovers. Open the window, turn on a fan, and it would be extremely difficult for anyone to smell it.
Please for the love of god do not smoke a hepa filter, that is such an insanely bad idea.
I spent about a year homeless... I've seen people turn absolutely everything into rolling paper for a rollie, spliff or joint. Newspaper, pages from a Bible, napkins....