Over the years I have seen and tested a large number of gadgets designed to get rid of toilet odours, from double walled ceramic toilets that had an exhaust pipe to the outdoors, to exhaust ducts that fitted under the tank and various carbon filters situated under the seat. Finally an New Zealand device has come out that got it right.
They fit a fan with a replaceable carbon filter right inside the toilet tank, which draws its air from the overflow tube. That means that it draws from inside the toilet rim, but without trying to make a special toilet. When you are sitting down, you act as part of the system allowing the fan to efficiently draw all the odours up into the filter. The entire thing is hidden inside the bowl so it makes for no extra cleaning problems. A motion sensor taped to the wall turns it on and off -- either wireless or wired. It is really well thought through and in fact it works. It may not be so nice to say, but you no longer have to fear tailgating someone who is just leaving the toilet. If there is no moisture source like a shower in the washroom, you don't even need an exhaust fan in the room, saving a lot of trouble for that extra toilet. In the master bathroom, you trap the odours before they fill the rest of the room.
It won't fit all toilets, but works fine on most. If you have a float ball, you will need to replace it with a more compact valve system as is common on most modern toilets. Most installations require very little work. Yes I do recommend this product. For more details than you ever wanted to know about a toilet, check out www.PanFan.com.
I just looked up this entry, 5 years after writing it, because I wanted to buy some more carbon filters for the unit that my wife has in her very busy office toilet. When I realized I had first installed that unit in 2007 and that my wife still swears by it -- I thought it was time to give this unit a very big long term durability thumbs up! There are lots of gadgets that have come and gone -- but the Pan Fan is the best and most durable I have found.