IAQ considers many factors, such as particle levels, humidity levels, VOCs (volatile organic compounds), and other airborne gases and microorganisms. Many of these factors can contribute to various health and comfort problems. For example, high humidity may cause the feeling of muggy air, which to many is uncomfortable. Not only will it be uncomfortable, but it can also inhibit the growth of unhealthy microorganisms. Furthermore, high particle levels, VOC levels, and other gases can irritate the lungs and throat when breathing, which is not an ideal, comfortable living condition.