odours

Hi all
after all the recent discussion on this delicate matter & the obvious problems people have plus finding out from bt that we can't install a new vacuflush type in our soon to be 20 footer (not enough room 21 minimum ) we were pleasantly suprised to find a SOG ventilation system at the sydney caravan show on the week end they are distributed by aussie traveller & cost $297 there are several different models including one for tethford they can be retrofitted they are basically a fan that vents via a hose through a charcoal filter ( no odour) & operates went you open the vent on the loo the claims is that with the increased air flow the natural digestion & break down are taken care of hence no need for chemicals by turning on the fan before you open the lid you releave the pressure ( chuckle) to the outside so no gush out of the tank into the ensuite the demo model had the vent in the tethford door but a new installation could be anywhere including through the roof
has anybody had any experience with these certainly our experience with holding tanks on boats was that provided you keep the charcoal dry & replace it every 18 months or so the vented odour was not detectable
cheers