Sumps and CO2
injection usually don't work too well together. I have seen it done, but not often. The least amount of surface disturbance is exposure to atmosphere is usually best for keeping CO2
You are not releasing enough CO2
into the room to cause any concern, however. Even if you were to dump the entire cylinder at one time, you'd be fine... but we are talking about releasing the contents of the cylinder of weeks, if not months, depending on tank size and injection rate.