I installed a cpu fan and some dryer vent hose to exhaust the catbox air to the outside. That worked pretty well except in summer green bottle flies would climb

I installed a cpu fan and some dryer vent hose to exhaust the catbox air to the outside. That worked pretty well except in summer green bottle flies would climb up the vent to get at the poos. Later a fox ate the cat. I think this was unrelated to the venting system, but it did eliminate the smell issue.