If it is a building with large volume and large space such as a stadium or exhibition hall, when it is necessary to set a super-scale aluminium casement doors, a regular size attached door can be added to the big door fan, so that people can pass when the door does not need to be opened.  

Nowadays, there are many inspection doors in all kinds of equipment tube Wells in the building.

It is not often through the place, so the general frame height is equal to or lower than the ordinary door, and the threshold with the same height as the skirting line is left below. The net height does not need to be limited to 2m, 1.5m or so.  Hotel room, door clearance height ≥2.1m.