POST-WAR BUILDING STUDIES NO. 29
298. Dealing first with the direction of opening, it is obvious that, ideally, all doors which may be used for escape should open in the direction of exit travel, so as to avoid the possibility of a door having to be opened against the pressure of a number of people trying to force a way out. Where there is only a small number of people in a room, however, this danger does not really arise (e.g. see Factories Act, 1937, Section 36 (2)-where a door is required to open out if there are more than 10 people in a room). In practice it may also be inconvenient in some cases for a door to open in the direction of exit travel, for instance, where a door opens on to a corridor, although this particular difficulty may be overcome by forming a recess for the door. The matter of practical convenience cannot, of course, be allowed seriously to prejudice life safety, and it is recommended that in all cases where the number of persons in a room or floor area exceeds 40, the doors serving it should, regardless of other considerations, swing in the direction of exit travel or both ways. All doors should open in the direction of exit travel also in buildings containing hazardous occupancies, as the possibility of rapid fire spread in these cases may make it essential to provide for the greatest possible freedom of movement in escape. Doors swinging both ways should be glazed with a panel of clear glazing to minimize risk of collision and where provided in fire-check doors this glazing should be fire resisting. Exit doors which have to be kept shut whilst the building is occupied should be fitted with panic bolts. If external to the building the working parts of such bolts should be of non-rusting metal. An exception to the rule given above can be made in the case of doors opening to the street which are kept locked back in the fully open position during the whole time the building is occupied by persons other than any resident staff. In such cases the doors may open inwards only.
Why has it increased over the years, 50 in the blue guide and now 60 when will it be 70?