I wouldn't draw air from outside you have a good chance of getting pests/ mold and temp fluctuations.
As for dispersing, if smell is an issue I would recommend a carbon filter. No need to vent outside if you do that.
You wont need a very strong vent fan if you are running LEDs, i would just make...
sup guys,
1. grind up your stems
2. put a pot on with about 2 cups of water and get it to a rolling boil
3. put your ground up stems in and turn the heat to LOW, put a cover on it- we'll check up in 5 minutes.
4. after your 5 has gone by, i suggest throwing a tea bag of your favourite tea.. i...