A renifleur is someone, can be male or female, who gets sexual pleasure from smells. This can be triggered by a particular smell which is why males and females can be more sexually receptive when a certain perfume or after shave is used. In very rare cases it can be triggered by ordinary, everyday, common smells which means that the subject must be kept in a sterile, odour-free environment.
Have you smelled the stench coming off Malcolm? He's enough to make the most ardent renifleur get nose plugs!