I would clarify that emergency zone is not a measure of response, but it's necessary really only when the presence of ships or persons might impede the intervention. There may be a very grave and imminent danger, but it may be in a remote area, a place where non-navigation or other traffic is present, and an emergency zone wouldn't need to be declared automatically to address the situation and intervene.
On February 26th, 2018. See this statement in context.