Wash. Rev. Code § 70.136.050
An incident command agency in the good faith performance of its duties, is not liable for civil damages resulting from any act or omission in the performance of its duties, other than acts or omissions constituting gross negligence or wilful or wanton misconduct.
Any person or public agency whose assistance has been requested by an incident command agency, who has entered into a written hazardous materials assistance agreement before or at the scene of the incident pursuant to RCW 70.136.060 and 70.136.070, and who, in good faith, renders emergency care, assistance, or advice with respect to a hazardous materials incident, is not liable for civil damages resulting from any act or omission in the rendering of such care, assistance, or advice, other than acts or omissions constituting gross negligence or wilful or wanton misconduct.
RCW 70.136.050