[ASHRAE Standard 62.2]:an indoor object, person, or activity from which indoor air contaminants are released, or a route of entry of contaminants from outdoors or sub-building soil.[ISO 16814:2008, 3.39]:persons, materials or processes (activities) from which indoor air contaminants are released.NOTE A source can also be a route of entry of contaminants from outdoor (e.g. air, soil, clothes).