Standard Orientation <water mist nozzles>
in the case of nozzles with symmetrical heat-responsive elements supported by frame arms, standard orientation is with the air flow perpendicular to both the axis of the nozzle’s inlet and the plane of the frame arms. In the case of non-symmetrical heat-responsive elements, standard orientation is with the air flow perpendicular to both the inlet axis and the plane of the frame arms which produces the shortest response time.
Source: Resolution A.800(19), Revised Guidelines for Approval of Sprinkler Systems Equivalent to that Referred to in SOLAS Regulation 11-2/12, 23 November 1995, International Maritime Organization. Regulatory Guidance