A process for locating a porosity-causing gas leak during manufacturing of a composite part, the process comprising: engaging the composite part with a gas impermeable membrane so as to contain the composite part within the membrane and define a flexible non-compartmentalized single volume between the composite part and the membrane, fluidly connecting at least one gas conduit to the membrane for flow of gas through the membrane, mounting in co-operation with the membrane a plurality of sensors, wherein said plurality of sensors are mounted in a spaced apart array relative to said part and in fluid communication with at least said single volume evacuating said single volume through the at least one gas conduit, using the plurality of sensors for detecting and measuring at least one characteristic of gas flow, at least during said evacuating, and at least in the single volume, and generating gas flow data corresponding to said detecting and measuring of said at least one characteristic of gas flow, characterised in that the process further comprises the step of computing gas leak information from said generated gas flow data by: determining combinations of pairs of sensors by employing a geometry of the composite part and locations of the plurality of sensors relative to the composite part; for each pair of sensors determining apex sets for all triangles formed from each pair of sensors, each said triangle having a base leg that extends to and between the pair of sensors and an apex defined at an intersection of remaining two legs of said triangle, wherein the remaining two legs have first and second lengths, respectively in proportion to corresponding first and second gas flow rates at the pair of sensors, respectively; for each pair of said apex sets determining: a) a point of intersection between said apex sets, or b) where there is no said point of intersection, a mid-point of a line joining points closest to one another between all of said apexes to provide possible leak locations. engaging the composite part with a gas impermeable membrane so as to contain the composite part within the membrane and define a flexible non-compartmentalized single volume between the composite part and the membrane, fluidly connecting at least one gas conduit to the membrane for flow of gas through the membrane, mounting in co-operation with the membrane a plurality of sensors, wherein said plurality of sensors are mounted in a spaced apart array relative to said part and in fluid communication with at least said single volume evacuating said single volume through the at least one gas conduit, using the plurality of sensors for detecting and measuring at least one characteristic of gas flow, at least during said evacuating, and at least in the single volume, and generating gas flow data corresponding to said detecting and measuring of said at least one characteristic of gas flow, determining combinations of pairs of sensors by employing a geometry of the composite part and locations of the plurality of sensors relative to the composite part; for each pair of sensors determining apex sets for all triangles formed from each pair of sensors, each said triangle having a base leg that extends to and between the pair of sensors and an apex defined at an intersection of remaining two legs of said triangle, wherein the remaining two legs have first and second lengths, respectively in proportion to corresponding first and second gas flow rates at the pair of sensors, respectively; for each pair of said apex sets determining: a) a point of intersection between said apex sets, or b) where there is no said point of intersection, a mid-point of a line joining points closest to one another between all of said apexes to provide possible leak locations. a) a point of intersection between said apex sets, or b) where there is no said point of intersection, a mid-point of a line joining points closest to one another between all of said apexes to provide possible leak locations.