intake question?

Yo what's up guys right now I have two seedlings that just started 4 days ago and I'm running only an intake fan which is just a regular 6 inch house fan since air is able to escape the closet since I didn't completely seal the closet up yet since I don't have my inline fan running. My exhaust is a 4 inch inline fan attached to my carbon filter which ill be running in flower. Right now I only leave the fan on when my lights are on. Once my plants start flower I'm going to completely seal the room closed. My question is I don't like running my intake fan all day because its just a regular house fan and not an inline fan or duct fan so I don't want to ware it out quickly by running it 24 hours so I was thinking, would it be fine to run that fan for when the lights are on and have it turn off when the lights are off but still have my filter running 24 hours? Would the filter still kill the smell and would this become passive intake since air will be able to pass through the fan still? Also the intake fan is the same fan that blows air on to my plants I only have a small grow box that is a 12/12 from start grow. If it helps the fan is a Honeywell turbo fan 6 inch house fan.

Passive intake is fine. You don't need an fan for intake. So long as exhaust goes through the filter, it will get the smell once you have some.

With seedlings, you need not worry about any of it. You do want air circulating/lightly blowing on the plants so the stems get strong.