A method of detecting fluorescence from bacteria suitable for determining the presence of faeces. The method comprises illuminating a target with excitation light and then monitoring the emission of fluorescence light from the target. The emission wavelength is longer than the excitation wavelength. The excitation wavelength can be 420 to 645 nm. The emission wavelength can be 650 nm or larger. The excitation wavelength can comprise a plurality of wavelengths corresponding to one or more porphyrin Q-bands. The target can be a container (e.g. diaper, nappy or incontinence pad). The light intensity can be modulated. The fluorescence lifetime can be detected. An optical fibre (30, fig 3) can be used. The method can comprise comparing the light emission to a predetermined threshold. The method can comprise a signal to notify the user to the presence of bacteria (faeces). A further aspect of the invention is a detection system for detecting faeces. The system comprises a light source (66, fig 6A), a detector (68, fig 6A), a source optical fibre, and a receiver optical fibre. The light source is coupled to the source optical fibre and the detector is coupled to the receiver optical fibre.
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