What Is "Fireproof"?

» The deadly fires in the LaSalle, Congress, and General Clark Hotels in Chicago have prompted city dwellers grimly to scrutinize the true meaning of the word “fireproof.”

by MAURICE WEBSTER

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FIREPROOF is a very reassuring term when you don’t know what it means. To say that a hotel is of fireproof construction means that it has been so designed as to eliminate the possibility of more than a minimum and predictable fire loss. Fireproof construction is the child of fire insurance and any safety to occupants is merely a by-product.

Had you been on the nineteenth floor of the LaSalle Hotel on the night of its great fire last June, you could have taken comfort in knowing that the fire could rage up to a temperature of 2000° F. over a period of four hours before there could be any danger of failure in the supporting columns. That no one could have survived such an ordeal is beside the point.

The hotel management could take comfort in knowing that with the replacement of superficial decorative surfaces, the hotel would again be ready for business. In the words of a consultant of the Underwriters’ Laboratories, “Such a building should be designed like a good stove, capable of containing an intense fire for a considerable length of time without danger of structural failure.”

The story of those hotel fires in which many lives are lost follows a pattern which is so repetitious that certain conclusions seem inevitable. This is the general pattern: An area in the ground floor — dining room, bar, lobby, or connecting store — bursts into flame so rapidly that fire-fighting equipment cannot prevent the first nearly explosive combustion. The enormous expansion of flaming gases creates its own draft, carrying smoke and fire up open stairways and elevator shafts. Each well or shaft is like a chimney except that the outlet at the top is safely sealed, while holes in its sides lead into bedroom corridors.

Temperature and atmospheric pressure in bedroom corridors rise rapidly, forcing smoke, carbon monoxide, and fire through transoms into bedrooms. Where windows leading to fire escapes are open the pressure carries smoke and flame across these exits, making them deadly. No fresh air can come in any window, for the pressure is always outward, except at the very base of the fire.

Panic conditions are created in corridors. Illumination and exit lights are completely blacked out by thick rolling clouds of smoke which blanket the ceilings. Guests cannot find exits through these dangerous corridors. The result is death from suffocation or burns. The post-mortem shows carbon monoxide.

For the safety of occupants these are the factors of prime importance: first, of course, to prevent fire; second, to extinguish fires in their incipient stages; third, to prevent the spread of fire; and fourth, so to channel the fire and fumes of combustion as to prevent their spreading in upper portions of the building and killing by asphyxiation. A great deal has been said on the first three subjects, but the proper venting of fire and gas is not very well understood, as the contradictory laws written into our building codes show. It is this subject that I should like to emphasize.

An understanding of the behavior of gases in combustion is necessary in the design of proper venting. When air is heated from 70° F. to 1500° F., — which is the temperature at the center of substantial construction fires, — the air expands to about four times its original volume. Added to this expansion is the expansion through combustion of any solid matter consumed, such as woodwork, furniture, or paint, which expands to between 100 and 150 times its original volume. This combination of heated air and gas is very light and its expansion causes great pressure when confined. It will break out adjacent windows or expand horizontally, spreading the fire into other rooms, when it cannot rise. In most of our worst fires, open stair wells or elevator shafts have carried the suffocating gases into bedroom corridors, where the greatest loss of life has occurred.

The enclosure of elevator shafts and stair wells is a very important safety measure, but even this has failed when not combined with proper venting. Automatic door closers — which close at a temperature of 155° F. — are standard equipment, but they are not infallible. The trouble is that people arc constantly blocking open the doors to these enclosures, for the convenience of guests or to obtain natural ventilation in corridors. Any safety measure which depends on vigilant and constant supervision will fail at times.

No stair well or elevator shaft is safe unless surmounted by a large vent which will open when fire or excessive pressures have entered. The first reaction of most unobservant people is that this vent is very dangerous, as it will make a draft and increase combustion.

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IN evaluating the merits of this device it is necessary to consider: (1) what will happen when fire and smoke have entered a shaft which is sealed at the top; (2) what will happen when it is wide open at the top.

In the first case, when fire or smoke has entered the shaft it is no longer of any use as a safe means of escape. The fire and dangerous gas, being blocked at the top, will travel horizontally wherever there is an opening, usually carrying fire into other portions of the building. Where a corridor door is open, all occupants of that floor are endangered by carbon monoxide and fire. All exits on that floor and those above have been made hazardous.

An open vent may stimulate combustion in the fire below, but it is futile to try to smother the flames except by some types of extinguishers. There will always be enough oxygen to support combustion, and if the intensely heated gas is not vented, it will either blow out a window and flame up the outside of the building or will spread into other rooms.

If the stair well or elevator shaft is so vented as to leave it wide open at the top when fire has entered, the fire will rush up and out as in a chimney. Then it will make little difference whether or not some corridor doors are open, because suction will always be into the shaft. Little fire or smoke will enter the corridor. For the scientifically inclined, a reference to Bernoulli’s Theorem (explained in any high school physics book) will be found to be pertinent. The fire below will be led towards this shaft, intense heat and inflammable gas will be drained off, and the danger of horizontal spread of fire will be reduced.

The LaSalle Hotel fire gave an instructive demonstration of these facts. The fire broke out and spread with extraordinary rapidity. The cocktail lounge was completely enveloped in flame within two minutes of the discovery of the fire. It swept into the lobby with great pressure before it blew the plate-glass windows out of the cocktail lounge. Less than two minutes later the whole lobby was ablaze and fire roared up the open stairways.

Occupants testified that within five minutes of the discovery of the fire, corridors as high as the seventeenth floor were so blanketed with smoke as to make lighted 60-watt bulbs completely invisible.

There was a small ventilator leading out of the cocktail lounge into an elevator shaft. This was much too small to have any appreciable effect on the pressures blowing the fire into the lobby. Flames shot into the shaft and rose twenty-two stories, being drawn by three 24-inch ventilators at the top. When the temperature of air going through these ventilators rose to 155° F., the ventilators snapped shut as required by a misguided ordinance. This instantly forced all rising gas out through elevator openings into corridors on all floors. Flames broke very quickly into the elevator shaft at the first floor.

So far the fire had followed the typical pattern. Many people had already been exposed to carbon monoxide, and flames were licking corridors from the mezzanine to the seventh floor.

By this time windows leading into the court were breaking out from the stair wells and elevator shaft. All windows in the elevator shaft from the second to the twenty-second floor, and in the stair wells from the second to the sixth, were avenues of fire: these openings formed vents which began to draw the flame and gases out. The fire department arrived. Firemen testified that there were not the usual pressures at entrances from expanding gas. As guests groped their way to fire escapes through blackened corridors, the dangerous pressures had subsided, and when windows leading to fire escapes were opened, no smoke blew out to rise in a column and endanger those above. Nearly a thousand people were safely evacuated by fire escape, since all normal public exits led through the lobby.

A study of the building after the fire showed white paths of clean floor leading out from under bedroom doors, all pointing in the direction of the elevator shaft. At other places the white marble was black as slate. This indicated clearly that once the windows had broken out in the shaft a positive suction had been established toward the shaft.

It is possible to carry out this principle to such an extent that no fire will develop a higher pressure in a corridor than exists in the bedrooms. Under these circumstances a bedroom in a fireproof building would be nearly 100 per cent safe from fires originating outside the room itself.

Most national advisory codes support the principle of venting by recommending skylights of plain glass or clerestory windows having an area of not less than 75 per cent of the cross-sectional area of the stair well or elevator shaft. This glass will break out under intense heat and the fire will vent itself. Fire-fighting authorities with whom I have talked have preferred a fusible link or some other more positive and rapid means of opening. It is the practice of firemen to get on the roof and break these skylights when they have not broken of themselves.

Many municipal codes and some state codes require solid concrete slabs over stair wells and shafts and, as in the LaSalle Hotel, require any ventilation to be self-closing when fire has entered the shaft. These codes are in direct conflict with one another and with common sense.

Automatic venting is required almost universally over fly galleries in theaters and in motion picture projection booths. Industries handling explosives, volatile oils, and paints have made wide use of this safety measure.

Safety to occupants of buildings is written into our building codes. The writers of these dull and infuriating documents seem to have fallen under the spell of the beautiful word “fireproof,” for they often relax their requirements for exits, enclosures, and other prime safety measures when considering the “fireproof building.”

Codes often permit 100 per cent of public exits to be channeled through lobbies without requiring rigid limits to combustible material or the protection of sprinklers. Minor stupidities in codes are frequent — such as a code requiring exit lights to be at ceilings, when, under conditions that make it urgent to find an exit, lights at ceilings are invariably obscured by smoke. Glass transoms over bedroom doors are fire hazards frequently overlooked by codes. Yet we know that transoms break out and permit the spread of fire, as in the recent Congress Hotel fire.

Spread of fire is conditioned by surfaces. Old “mill construction” permitted no paint or varnish other than cold-water paint because it was found that oil-bonded paints spread fires very rapidly and gave off a dense black smoke. This was rediscovered by the Navy after a disastrous transport fire in mid-Atlantic. The Navy and the Bureau of Standards have done considerable research in this direction and have developed some very good paints.

If you doubt the hazards produced by many coats of paint, take a piece of tin one foot square having fifteen coats of oil-bonded paint thereon, and place it over a lighted burner on the kitchen stove. Then note how the eyes sting; note the black smoke on the ceiling and the anguished cries of the housewife. Multiply this effect several thousand times and you will have a reasonable facsimile of a hotel corridor in a bad fire.

It is suggested that the use of oil-bonded paints be discouraged in stair wells and at least, on ceilings of corridors, lobbies, and cocktail lounges. Ceilings are critical because heat always stratifies and hugs the top of any enclosure, looking for a way up and out.

We are rapidly covering the ceilings of our corridors and principal rooms with acoustic materials. So far as I know, no study of the relative flamespreading characteristics of these varied materials has been made. Such a study seems imperative.

We must not permit our codes to multiply construction costs by more and more restrictions and requirements. By overdoing it we can make their enforcement impossible and turn them into instruments of extortion. A study of codes to eliminate present unnecessary exorbitant requirements and to plug up dangerous omissions — this, combined with education, will encourage voluntary compliance where it is most urgently needed.

These are my conclusions drawn f.om a study of many dangerous hotel fires: first, that these fires generally originate in ground floors or basements; that most deaths occur on the bedroom floors; and that most of these deaths are due to suffocation or entrapment.

Thus it follows that for safety we must give close attention to: —

1. Hidden spaces and closets, where fires are born.

2. The amount of combustible material and the flammability of surfaces in lobbies and connecting areas. Sprinkler systems should be installed where conditions permit.

3. Proper protection between lobbies and sleeping areas.

4. Proper venting to keep gas and combustion pressures out of bedroom corridors.

In my opinion, and in the opinion of several other members of the investigating juries, all of the fourteen lives lost in the General Clark Hotel fire could have been saved by the expenditure of about $2000 for self-closing doors into corridors and by substituting plain glass for wire glass in the skylights. And in the LaSalle Hotel all but the employees who remained in the lobby cashiers’ cages too long, and possibly the telephone operator, might have been saved by the same changes. At a considerably greater expense the installation of automatic sprinklers would probably have saved all sixty-two lives lost in the LaSalle Hotel.

Finally, let me add one very human footnote. If you are really interested in safety, you will be most careful about smoking in bed. This practice contains more individual hazard than that of inhabiting a fireproof hotel. Some day a practical flame-proofing will be developed for bedding. In the meantime some communities have made it illegal to smoke in bed. Does enforcement seem impracticable? Well, a stiff fine and the fear of an irate landlord might have an inhibiting effect. Otherwise we shall have to continue to rely on fire.