I use Ona Gel and i can vouch for i being good
It's not an air freshener ...So it don't make the room or your plants smell of it... it has a nice smell but you have to sniff the pot to smell it ... It acts as a neutralizer .
If your room is tight and your filter is working it's pointless putting it in your grow room ... the filter will scrub the air on the way out ... It's more effective at the end of your extraction run .
You can connect it inline to your extraction ( before or after your fan) if you use a T-Pipe like this
air passed over it will be neutralized befor it get out of the pipe .
You can also spill some out into smaller containers to place around your room / house ...it has the same effects
Hope that helps
Peace