Washington State offers several programs for emergency volunteers:
Temporary Emergency Workers, and Registered Emergency Workers. These are covered in Chapter 118-04 WAC. Fortunately for all of us, Michael and Catherine Cochrane dug into this issue and spotted a number of issues - which have since been rectified - and they will hopefully provide a summary of the requirements and resources of interest to REWs here in the future.
Liability issues are also covered in RCW 38.52.198.