Abstract: A virtual impactor that can remove essentially all of the particles from an airstream is disclosed. Disclosed are a method of separating particles from the airstream using this virtual impactor, a method of concentrating the particulate matter in an airstream, and the concentrated airstream.

Abstract: A nonwoven fiber and fabric and process for production are provided which have comparable strength characteristics to conventional fibers and fabrics and are of a finer diameter. This is accomplished through a process of producing a nonwoven fabric made from at least one polymer which has a melt temperature between about 410.degree. and 470.degree. F. (210.degree. and 243.degree. C.), xylene solubles between about 3.5 and 7.0%, a melt flow rate between about 30 and 45, and an isotacticity of at least about 94%, extruding the polymer through fine openings, drawing the polymer to produce fibers of a denier of 1.4 or less, and then depositing the fiberized polymer on a collecting surface to form a web of disbursed fibers.The nonwoven fabric of this invention may be used in products such as, for example, diapers, feminine hygiene products, adult incontinence products, wound dressings, bandages, sterilization wraps, surgical drapes and wipers.

Abstract: A virtual impactor that can remove essentially all of the particles from an airstream is disclosed. Also disclosed are a method of separating particles from the airstream using this virtual impactor, a method of concentrating the particulate matter in an airstream, and the concentrated airstream.

Abstract: A volumetric flow controller is used in connection with a virtual impactor classifier to control two separate flows in separate lines from an air pump. Each line has a flow control valve controlled in response to flow signals that are obtained from a pressure transducer that provides an electrical signal proportional to pressure. Pressure changes are sensed and the provided electrical signal is compared with a reference and will actuate a damper motor and move a flow control butterfly valve in the flow line for adjusting the flow when the pressure signal is different from the reference. The circuitry used provides for a dead band, so that changes in the butterfly valve setting will not occur unless the flow varies a selected amount, and also a timer control is used so that the motor operating the damper will be operated only at selected time intervals to prevent "hunting" or continuous operation of the valves. Further, temperature compensation signals can be provided as desired.