Detector inlet and sampling method

A method of detecting a substance of interest in a sample of vapour obtained from a flow of fluid carrying particulates, the method comprising:

• directing the flow of fluid carrying particulates past a sampling inlet;
• varying the shape of a distribution of particulates, transverse to the direction of flow, relative to the shape of said distribution upstream of the sampling inlet, so that the particulates carried by the flow are inhibited from flowing through a sampling volume around the sampling inlet;
• obtaining at least one sample from the sampling volume via the sampling inlet;
• and
• providing the sample to an analytical apparatus configured to detect the substance of interest.

A detector comprising:

• an analytical apparatus for detecting a substance of interest, and a detector inlet, the detector inlet comprising:
• a flow passage for carrying a flow of fluid, the flow passage comprising a sampling volume;
• a sampling inlet adapted to collect samples of the fluid from the sampling volume as the fluid flows past the sampling inlet, and to provide the samples to the analytical apparatus, wherein the flow of fluid carries particulates;
• and
• a flow director arranged to vary a spatial distribution of the particulates carried by the fluid to increase a relative proportion of the particulates carried past the sampling inlet along the flow passage without entering the sampling volume, wherein the flow director at least one of:
• a) protrudes into the flow passage from a wall of the flow passage;
• b) is tapered so that it is narrower towards an upstream end than it is towards a downstream end;
• c) comprises a recess in a wall of the flow passage, wherein the sampling inlet is arranged in an upstream wall of the recess;
• or
• d) comprises a series of foils.