A system for converting propelling thrust to produce a continuous flow is provided. The system can be integrated and/or retrofitted to the body of an aircraft. The system includes a pressure-lowering device and a sample chamber. The pressure-lowering device is used produce a low-pressure, continuous flow from a high-velocity propelling thrust source. Moreover, the pressure-lowering device is a passive flow generator that does not require a power source in order to produce a continuous flow from a propelling thrust. The design of the pressure-lowering device produces a flow rate that is independent of the aircraft motion. The sample chamber is used to measure and analyze ambient gases which are pulled through the sample chamber by the pressure-lowering device, as a result of the high-velocity air stream produced by the propelling thrust source.