As in is it possible to have a hidden grow box in my room with no smell? Or outside in a place thats hidden but close to people will they smell it?
There pretty smelly, You will want to get a carbon filter indoor. Outdoor's I would imagine you just need to let it do it's thing. and it probably will smell just be more dispensed into the air. I have not done outdoor yet though.
its possible to have a hidden grow box though you would need either a carbon filter or a ona bucket. both require a fan and then you need to think about sound produced from that. its really hard making a 100% secret grow box.