Easy! Besides air freshner, scented candles & fan forced charcoal air cleaners; totally close off & lock the room your grow is in (stuffing towels & whatever under the door), then LIE YOUR FUCKING ASS OFF! Yep, that right, I'm advising you to LIE to mom & dad! Go ahead & make yourself sound like a total pig! Its your storage & all your dirty laundry, smells like old gym socks, sorry guys, I'd be too embarrassed to let you go in there! Etc, etc, etc. Use your imagination, its your lie, tell it like you want to. That's my story & I'm stickin' to it!
(That's why god gave us big mouths, so we can lie our way out of shit!!!!)