252 FIREPROOF CONSTRUCTION features; in large retail establishments safety of life and contents are both to be considered; in nearly all manufacturing establishments special hazards deserve attention — materials and processes which are more or less peculiar to the special industry. The importance of this latter factor is apparent from the attention devoted to it by fire underwriters and fire protection engineers. The isolation of danger ous features of production by confinement to separately safeguarded buildings, floors or com partments will serve to decrease loss of life, reduce the extent of material damage and elim inate consequential loss through subsequent dis turbance of work in other departments. The importance of the above considerations, though readily admitted and indeed self-evident, is often overlooked and submerged in the mass of construction details, as is evidenced by many notable fires of the past.
z. Limitation of Occupancy.—Private enter prise and public regulation necessarily go hand in hand in the repression of unnecessary fire loss. The preceding paragraph has referred to buildings designed for a particular occupancy, but through economic changes buildings are often diverted from their original purposes and the character of occupancy entirely changed. In order to guard against possible unfortunate results from such changes careful municipal regulation is necessary. While great restric tion is obviously impossible, some limitation of the number and character of tenants is abso lutely requisite to avoid at least partial nullifi cation of original designs.
3. Stairways, Elevators and Fire-escapes. Aside from provision of emergency exits such features must be considered as facilities for fire-fighting and possible avenues of fire trans mission. They furnish exceptional assistance when adequately isolated so as to be safe for firemen, while on the other hand insufficient and unsafe provision is merely a detriment and a menace to the safety of persons as well as property. The importance of all floor openings in the transmission of fire is readily perceiv able. Fire-resisting floor construction is of
little avail if unprotected vertical passages are introduced. Just as fire-resisting material in walls should be supplemented by window pro tection, so should vertical openings in other wise non-communicating floors be supplemented by protection of floor openings. In a sense the entire Baltimore conflagration is ascribable to neglect of this principle, since otherwise the fire might have been extinguished or controlled at its inception. The protective methods are more fully discussed later.
4. Exposure Hazard.— The site of the pro posed building is a governing factor in its de sign by reason of the existent surrounding hazards. At least 25 per cent of fire losses are due to exposure. Against particularly danger ous neighbors blank brick walls or at least walls with but few openings of minimum size should be provided. In this connection the character of the roof is not to be neglected.
5. Subdivision of Area.— This is an accepted fundamental feature of fire-resisting construc tion, from which has developed the analogous idea of the subdivision of city areas by °fire walls.° In the first place it localizes the fire by confining it to the unit of area of origina tion, thus definitely limiting the consequences.
Thus the entire compartment contents may be destroyed and the trimming consumed without appreciably affecting the remaining area. Even more or less inadequate partitions will prevent strong drafts and furnish barriers for fire fighting. Secondly, just as a building with non-resistive floors may become a gigantic ver tical flue so may a single undivided floor assume the function of an immense horizontal flue. The division of area prevents strong drafts from the openings nearest the exposure across the building to those opposite. Past conflagrations are testimonials of the accel erated transmission and the greater intensity of fire on undivided floors. Thirdly, a large area presents additional difficulty in fire-fight ing, augmenting the difficulty of surrounding the fire, setting out the apparatus and the cover of smoke.