How fresh must the air be for indoor grow?

I am just wondering cause I am making a setup soon
Is it obligatory to have ventilation that brings the fresh air from outside ..
or are the inside fans and tent vent sufficient?

If the room your tent is in has ac or some type of air system similar then you should be fine. You would just need to have a exhaust fan exhausting air out of the tent, this will create a passive intake where the air is naturally pulled into the tent because of the vacuum you have created.
Check out subcools post about venting your grow room.

https://www.rollitup.org/subcools-old-school-organics/50791-venting-grow-room-efficiency-get.html

depens on plant size, if you growing huge fat buds you want lots of air movement. doesn't have to all be fresh though, you could leave a window open a tad or ac on like thekoc said

fo88hrabrim said:

I am just wondering cause I am making a setup soon
Is it obligatory to have ventilation that brings the fresh air from outside ..
or are the inside fans and tent vent sufficient?

Click to expand...

when the plants are small you can probly get by with just opening the tent a couple times a day. but once they start growing and filling up the room, you will want to have an exhaust fan sucking out the air and fresh air coming in or you need to be completely sealed and add co2.

you still want a circ fan for air movement along with ventilation for fresh air.