You will need ventalatoin of some sort or co2 one of them will be needed though you didnt mentoin if you were in a sealed room or if they are getting fresh clean co2 from somewere as i presume they must be. plants need co2 to grow so if they arent getting much now you will need to fix it so they dont die if the 9ft squre place is a room ,is there a vent? anyway to answer you questoin yes you will need ventalatoin from some source.Be safe the postman.