Sure, I use a Coway Airmega AP-1512HH set to low permanently. It doesn't move a ton of air on the low setting, but it is very quiet and the size fits pretty wel

Sure, I use a Coway Airmega AP-1512HH set to low permanently. It doesn't move a ton of air on the low setting, but it is very quiet and the size fits pretty well next to the robot. I think getting something quiet is key as to not spook your cats, as one of mine hates the sound of loud white-noise-ish sounds. I will say I think this one works well, but you could likely find something cheaper because you don't need to much air circulation for a litter box. I just happened to already have this one.