A toilet including: a toilet pan having an interior and a flushing outlet; a toilet cistern having an interior; a cistern overflow pipe in communication with the toilet-pan interior; a collar for connecting the flushing outlet to a sewer discharge pipe, the collar having a passage through it with exterior and interior ends; a fan within the cistern interior and having a fan inlet and a fan outlet; and a duct for gas communication from the fan outlet to the passage exterior end, the fan adapted to draw gas from within the toilet-pan interior through the overflow pipe and then propel it into the duct, through the passage and into the sewer discharge pipe.