In some ships on a very few doors or hatches which would normally be governed by a watertight control marking but which must be open for recirculation of air.
Kwezinye iinqanawe kwiminyango embalwa okanye izivuli ezinokulawulwa ngempawuzolawulo elungangenisi manzi kodwa ekufuneka zivulelwe ukujikeleze komoya.