I have 2x 12x16 Nova processors. 1 x 3 bath for colour and a 1 x 2 bath for the stop/fix stage of B&W. Yes they give off an odour but it is not very strong and then only for the RA4 developer. I have been using them for about 24 years now and never had a problem even without ventilation. the smell is slightly noticeable when you first go into the darkroom after they have been warming up but it is not objectionable at all.
They have a very small footprint with regards to the exposed chemicals and this I think compliments their ease of use and environmental friendliness for use in a house. I would not even think about any need for fitting a forced ventilation system.
One hint which will reduce the smell and prolong the life of the RA4 developer is to cover the whole top of the processor with cling-wrap after use and replenishment of the chemicals. If you get a good seal, and that isn't difficult, the surface of the cling wrap will show a small vacuum depression as the chemicals cool and contract. My current RA4 mix is now approaching 10 months old and with regular replenishment (100cc's per 80sq ins of paper) it should last almost indefinitely.
Even after cleaning out the tanks can be done by draining the chemicals, washing the accumulated sludge with the appropriate cleaner then THOROUGHLY washing the tanks out again before replacing the dev, stop, and bleach.