1. A fuel tank inerting system for an aircraft comprising:a first air source;
a second air source, wherein the second source includes air provided from an outlet of a primary heat exchanger of an environmental control system;
an air flow including a mixture of air from the first air source having a first temperature and air from the second air source, distinct from the first air source, having a second temperature, the second temperature being cooler than the first temperature; and
at least one air separating module configured to separate an inert gas from the air flow.