Abstract: A fluid stream sampler enables variable flow rate controlled air sampling, as an attachment to a vacuum source, typically a household vacuum cleaner. The fluid stream sampler includes a housing body having a vacuum outlet opening and a sampling port inlet. A volumetric flow rate indicator is disposed in the flowpath between the vacuum outlet opening and the sampling port inlet. An adjustable damper panel interposed in the flowpath regulates the vacuum pressure within the housing body. In operation, a vacuum imparted by the vacuum source directs a fluid stream along the flowpath between the vacuum outlet opening and the sampling port inlet such that, upon moving the damper panel to a desired position within the flowpath, a desired volumetric flow rate is achieved as measured by the indicator. The desired volumetric flow rate corresponds to a preferred flow rate specified for a fluid constituent sampling medium interposed in the flowpath at the sampling port inlet.