DMC is a numerical rating of the average moisture content of loosely compacted organic layers of moderate depth. The code indicates the depth that fire will burn in moderate duff layers and medium size woody material. Duff layers take longer than surface fuels to dry out but weather conditions over the past couple of weeks will significantly affect the DMC. The system applies a time lag of 12 days to calculate the DMC. A DMC rating of more than 30 is dry, and above 40 indicates that intensive burning will occur in the duff and medium fuels. Burning off operations should not be carried out when the DMC rating is above 40.