Grow tent question

Hi to all your rollitup guys. I have a question about when your light are out do you keep your exhaust running to keep down the smell.

That question depends on many factors

primarily you need to allow for a change of air in your grow room at least once every 3-5 minutes. If you are running co2 you can have higher temperatures and thus running fan less is also possible, but if your temperatures struggle even during the night cycle it is a good idea to continue exhausting air.

your plants like the most stable environment possible, if your struggling with cold air you may need to either heat the room the tent is in so you can have a steady intake of consistent air or cool during the summer.

regardless of co2 or air temps you always need to circulate the air, so short answer is yes, but you could run it on a timer on/off

Keep in mind plants essentially breathe air and co2, So without replacing the air around them they will basically suffocate. In addition you have temperature and humidity issues to be controlled via adequate ventilation.

Air exchange 2x per minute in a non seled grow is ideal.

And you best get tgat fan running at night,humidity spikes once the lights go out.