It shall be prohibited:
A. 
To accumulate or store except in approved locations any highly flammable or explosive matter, such as paints, volatile oils, cleaning fluids and similar materials, or any combustible refuse, such as waste paper, boxes, rags or similar materials; and
B. 
To accumulate or store materials on fire escapes or stairs, in stairways or passageways, at doors or windows, or under public stairs or in any other location where in the event of fire such materials may obstruct egress of occupants or interfere with fire-fighting operations.
A. 
Walls and ceilings shall be maintained free from cracks and openings which would permit flame or excessive heat to enter the concealed space.
B. 
In buildings of mixed occupancy, nonresidential space shall be separated from residential space by approved fire separation which will retard the spread of fire in accordance with generally accepted standards.
Interior finish materials for acoustical correction, surface insulation and decorative treatment of the surface of walls and ceilings and interior trim shall be of materials that will not, in burning, give off excessive amounts of smoke or toxic gases.