Abstract: An in-line filter rack includes a chamber for housing at least one filter, an inlet opening providing access to the chamber and configured to be coupled to an upstream portion of a return air duct, and an outlet opening providing access to the chamber and configured to be coupled to a downstream portion of the return air duct.

Abstract: The present invention relates to a method of assessing the condition of a duct along which a gas is flowing. The method comprises producing one or more sensor carrying elements, wherein the elements are formed to have selected parameters; introducing the sensor carrying elements into the flowing gas; and selecting the parameters of the sensor carrying elements such that the elements are transported along the duct by saltation. The present invention also relates to a method of reducing leakage through a leak in the duct.

Abstract: An apparatus includes one or more sealing elements to be transported along a duct by the flow of fluid therein at an internal pressure and to be drawn to a leak by the pressure differential resulting from a reduced pressure associated with the locality of that leak. Each sealing element has a body formed from an elastic material to have one or more impermeable bubbles filled with gas so that the sealing element has a volume which varies resiliently according to the change in volume of the bubble(s) in response to externally applied pressure. The product of the volume of the bubble(s) and the pressure of the gas therein is selected to provide a sealing element having a transport volume at the internal pressure which is appropriate to enter a leak and which, in response to the reduced pressure associated with the locality of that leak, is capable of increasing in volume from the transport volume sufficiently to seal that leak.

Abstract: A method for estimating a location of a leak (x) in a pipe (1). A liquid of a known density is fed into the pipe at a first inlet pressure (P1). When the liquid achieves a substantially steady flow rate, the flow rate passing into the pipeline is recorded. This step is repeated at a second, different, inlet pressure (P2). Using this data, an estimate of the leak location (x) and the area of the leak is calculated by simultaneously solving an expression which is based on relating the frictional energy losses of the liquid travelling through the pipeline (1) to the pressure in the pipeline at the leak (Pleak) and the flow rate of liquid from the leak.