does carbon filter push out or pull in?

hello i just got my new 400 watt setup and everything. i was wondering if the carbon filter pushes air out or it sucks in the air to clean it out. thanks.

My understanding is the filter (when attached closely to a fan/ducting can work either way but it's better when air is pulled through it.

have the fan suck the smelly air thats going to be exhausted from the grow area through the filter.

Have the fan suck air through the filter... if sucking air through it creates a negative air pressure and is much less stressful on your fan then pushing air through the filter creating positive pressure on your fan, making it work harder... sucking through the filter also keeps the dust and garbage out of your fan