 For example, to preclude one workgroup welding or grinding in the vicinity of another venting explosive or flammable gases.The permit to work system is for work being performed in accordance with pre-approved procedures and that has been macro scheduled, the purpose is to prevent conflicting short term activities of different workgroups to prevent hazardous interference.Once a permit to work has been issued to a workgroup, a lock-out tag-out system is used to restrict equipment state changes such as valve operations until the work specified in the permit is complete.