A safe sequence of operations is enabled through transfer of keys that are either trapped or released in a predetermined order. For example, a key is used to isolate a power source (circuit breaker or supply valve), this key is then released and can then be used to gain access through a gate or door to a high risk area by inserting it into an access lock. The key will then remain trapped until the gate or door is closed. A personnel or safety key can be released from the access lock, this ensures that the gate or door can not be closed and the initial key released until this personnel or safety key is returned (assuming that no duplicate keys are available).