To exempt certain doors from the application of Sentence 3.1.8.11.(1), which would otherwise require the door to be closed after each use, if certain conditions are met to automatically close the door under fire conditions. This is to limit the probability that fire will spread from one fire compartment to another fire compartment, which could lead to harm to persons in the other fire compartment.
To state the application of Sentences 3.1.8.12.(2), (3) and (4).