Freshly sawn timber contains between 30 and over 100 percent moisture content depending on species and must be dried before use. Natural air drying outdoors takes months to years, whereas technical kiln drying is completed within a few weeks. In kiln drying, temperature, humidity, and air circulation are precisely controlled to avoid drying defects such as cracks or warping. Target moisture levels for structural timber in construction are typically 12–18 percent, while interior finishing elements require 8–12 percent. Wood that is too moist will shrink after installation and can cause structural defects. Moisture content is monitored using electronic resistance meters or dielectric measuring devices.