There is provided a particle detection apparatus (30) comprising: a channel (32) including an inlet and at least one channel wall, the inlet permitting light to be introduced into the channel (32), the or each channel wall being arranged to define a channel path through which light may propagate; a light source (34) configured to introduce light into the channel (32) via the inlet, the channel (32) being shaped to guide the light to propagate along the channel path for illuminating a particle or a plurality of particles located in the channel path; and a monitoring device (36) configured to detect scattered light that is created by the illumination of the or each particle by the guided light and that leaves the channel (32) by passing through the or each channel wall.