John Ripley Freeman.

On the safeguarding of life in theaters; being a study from the standpoint of an engineer online

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smoky fireplace. The roaring fire on our hearth sends ninety
or ninety-five per cent, of its heat up the chimney and gives out
no smoke into the room, if only the chimney be properly designed
and the damper open. An ordinary rule is to make the throat
of the chimney at least one-tenth the area of the fireplace open-
ing, or it may be stated that the space through the damper should
be one-eighth the area of the hearth, and when we simply provide
an adequate chimney area and a damper that will surely open, we
shall have adopted a safeguard that would have saved four-fifths
of those who perished at the Iroquois, regardless of defective
curtain, defective exits and absence of fire hose on the stage.

In a way, it has been long recognized there should be a large
ventilator o^er the stage, and one city has copied from another
the building law that in the case of New York City reads as fol-

" There shall be provided over the stage metal skylights of a com-
bined area of at least one-eighth the area of the stage, fitted with
sliding sash and glazed with double thick sheet glass . . . the whole
of which skylight shall be ,o constructed as to openjnstantly on the
cutting or burning of a hempen cord . . . Immediately underneath
the glass of said skylight there shall be wire netting. . . ." etc.

The evident purpose of the thin glass is to cover the vent
with something that will break out under heat if the mechanism
for sliding the cover off fails. The wire netting is to catch any
piece of broken glass from falling to the stage.


The building law of the London County Council reads much
the same, save that its ratio is one-tenth, and perhaps that
ordinance is where the rule began.

Some of the leading American cities make the proportion one-
tenth. In the revised Chicago ordinance, notwithstanding their
fearful lesson, they are content with ventilators of one-twentieth
the net area of the stage, because, as one of the Aldermanic Com-
mittee gravely assured me, "If the area was made too large, it
might cause a down draft." What stupidity!

The idea of a large ventilator expressed in these rules is all
right, but the execution is commonly all wrong, and needs some
good engineering to provide a design of damper with careful de-
tails that will be sure to work. Note the antiquated, good-for-
nothing suggestion of the "burning of a hempen cord," when
fusible links have been used on the fire doors in your factories
for twenty years! There is no good reason to expect the hempen
cord in this position in smoky atmosphere from which oxygen
had been largely removed would burn off until after a majority
of the people in the gallery had been suffocated.

And in one of the newest and best of the New York theaters I
found the ventilator had a broad sheet of heavy canvas laced
tightly across its opening with marline, because, as the stage
carpenter told me, l i the cracks around the ventilator let in too
much cold air. " No building inspector had objected, and the
carpenter could not be made to see any danger. "It would
burn off in any bad fire," he said. So it might, but not until
the people in the gallery were mostly dead.

The requirement of thin glass in the building law is well meant,
but it would be too slow in breaking out. Remember how quickly
unconsciousness of suffocation comes in an atmosphere of smoke.
The wire netting called for is a positive danger, as often applied.

One of the most experienced theater managers in America told
me frankly that he knew the smoke vents on the theater which
he then occupied would probably not open in winter unless a man
should first pry them loose with an iron bar; but, said he, "I
have not heretofore seen anything better," and so after the Iro-
quois he had set his stage carpenter at work to invent something.

Doubtless, there are good smoke vents here and there that
have been designed and built with skill and conscience, for
the problem is not so very difficult, but I have not yet seen one of
these vitally important pieces of apparatus in which the design



Randolph St.


had been worked out with reasonable degree of perfection of de-
tail. " Something good enough to pass the building inspector"
appears to have been the current specification, instead of the


proper specification of " a vent of ample area that will be sure
to open wide, instantly, without human intervention, and that can-
not l)e stopped ~by warping, settlement, obstruction, frost, snow,
rust, dirt, or ordinary neglect"

I do not know who first fixed this ratio of one- tenth for size of
ventilator, the same figure that appears in the old rule of the
London County Council. Its author may have built wiser than
he knew, or may have taken it from the well-proved ratio of the
common home fireplace chimney. It works out as safe when
computed mathematically on theoretic grounds from the uncer-
tain data. The material is so favorably disposed for ignition that
the rapidity of combustion is largely a question of the air supply.

I am led by computation and precedent and the need of some
factor of safety, to concur in the wisdom of the ratio of one-
eighth or one-tenth, as already specified by the building laws of
the great majority of our American cities, and I believe it wise to
base it upon the gross area of the stage floor rather than upon
proscenium opening or cubical contents of the stage.

I have seen here in New York, in a recent theater, a case where
the inspector had, perhaps temporarily, forgotten the wording
of the law and figured it on the area directly in behind the curtain,
omitting much of the floor space at the sides. This is wrong be-
cause, given a large stage, there is a well-proved tendency to per-
mit an unnecessarily large amount of combustible material upon
it, and it not infrequently happens that the scenery of next
week's new attraction may be found stored at the side and rear
during the Saturday night performance.

I was earnestly desirous of making some practical tests in the
Iroquois, for the additional flames could have caused no injury
beyond that already wrought, and the practical demonstration
which I am confident would have been given regarding the
efficiency of automatic sprinklers and proper smoke vents would
have hastened their general introduction. Of course such tests
would have been made under greatest precautions and with city
fire department at hand in force, but while many of the most
important interests readily consented a few of those owning
surrounding property objected.

The Austrian Experiments of 1885.

Following the great theater fire in Yienna, a committee of the
Austrian Society of Engineers (Yereines der Techniker, in Ober


Osterreich) built a model of the Eing Theatre on one-tenth of its
lineal scale, which thus contained only one-one-thousandth of
the cubic contents of the original, and made many tests and
experiments. .

The experiments were divided into two groups, the first com-
prising those in which no ventilators were opened over the stage,
while in each of the experiments of the second group two ventila-
tors were opened, having a combined area which according to the
scale of their drawing I find was very nearly one-tenth of the area
of the stage. In the first series of tests made by igniting sheets
of paper hung to represent the scenery, but containing proportion-
ally far less combustible material than is often hung on a theater
stage, they found that the expansion of the air caused by the heat
quickly forced the curtain outward from the proscenium arch, and
within about twenty seconds from lighting the fire, this heating
of the air produced an excess of atmospheric pressure, much
greater than that of the ordinary pressure of city gas, thereby
explaining why it was that the lights in the Eing Theater became
so quickly extinguished after the outburst of the fire.

In the second series of these Austrian experiments, their models
of the ventilating shafts were closed by sheets of paper, and as
soon as these smoke vents burned open, all excess of air pressure
disappeared from the auditorium, and indeed, the updraft drew
the proscenium curtain inward over the stage.

During these experiments an unexpected warning was given
against covering smoke vents by wire screens, for it was found
the flying bits of charred paper carried up by the draft almost
completely closed them. To show how little this warning of the
Austrian Society of Engineers has become incorporated in current
practice, I may call attention to the building law of New York
City, which requires that underneath all of these skylight open-
ings designed as smoke vents, wire netting must be stretched;
the law apparently never considering how quickly this will
become so clogged as to destroy in large part the utility of the
smoke vent. At my visit to the remodeled Iroquois, I found the
openings in their new ventilating shafts screened by wire netting
in a way that would probably within a minutes time put them
into a condition of uselessness because of the fragments of burn-
ing cloth and embers with which they would be immediately
covered under the strong updraft, all of course with approval of
architect and building inspector!


The committee of the Austrian Society of Engineers concluded
that the outburst of flame and smoke into the upper part of the
auditorium and the extinguishment of gas lights in a theater
could all be prevented l>y providing adequate smoke vents over
the stage, and places these smoke vents as the feature of first im-
port in safeguarding life in theaters, and says that without them
emergency exits and fire curtains will be of no avail; and in
this conclusion I most heartily concur, for I had independently
reached it from my investigations following the Iroquois disaster,
prior to learning of the experiments of the Austrian engineers.

Regarding the mechanical construction of these smoke vents,
the Austrian committee says, " It is necessary that these be opened
instantly upon the outbreak of the fire; mechanical contrivances of
iron to be operated by human means will certainly fail, for, ac-
cording to all experiences in theater fires thus far, fright on the
part of the employees prevents the use of such arrangements."
They warned against automatic contrivances whose action may
be interfered with in consequence of rust or expansion by heat,
and against sheet iron valves falling inward by their own weight,
which might be restrained from falling open by the excess of
pressure due to updraft, and finally recommended that these shafts
be closed by a quickly combustible tissue of hemp or jute covered
with varnish or celluloid, and with a hole about one and one-half
inches in diameter in the center to invite quicker ignition. Our
Austrian friends were unfamiliar with the American fusible- solder
link, which is certainly quicker and safer and in every way far
more practical than any such tissue of varnished hemp.*

* Austrian Experiments of 1905.

While revising the proofs of the above for publication in the yearly volume,
report comes of a second series of tests on a somewhat larger scale, made on and
about Nov. 22, 1905, in Vienna at the expense of the Austrian government,
on recommendation of the Austrian Engineers and Architects Association. From
the brief preliminary report in Eng. News of Jan. 18, 1906, the following is taken:

The model theater, constructed of reinforced concrete especially for these tests,
had a stage 24.6 ft. wide, 19.7 ft. deep, 25.3 ft. high, with a proscenium opening
11 ft. wide and 8.5 ft. high. The auditorium was 18 ft. wide, 23 ft. deep, 15.4 ft.
high, or in general had about ^ the linear dimensions of the ordinary theater, and
therefore about ^V of its cubic capacity.

The tests made by burning old scenery and sheets of paper, representing pro-
portionally the amount of combustible for two performances, showed that with
smoke vents of total area of 11 per cent, of the stage area opened, the smoke
ascended through these vents over the stage with no suggestion of danger to the
persons in the auditorium, except that near the proscenium opening the heat was
somewhat severe.




Fusible Links for Opening Smoke Vents.

These links have been in common use on automatic fire shut-
ters and fire doors in our factories for twenty years. Three
types of these links are shown in Fig. 4. Each is reliable,

On the other hand, in tests with stage vents closed and curtain down, it was
bulged out toward the audience and lifted from the floor at the bottom, and
the auditorium was soon filled with smoke.

In a later experiment with sprinklers spraying the fire, on opening a door or
ventilator in the auditorium gallery some steam and hot gases were drawn into
the auditorium, notwithstanding the stage smoke vents were open.

As a whole these tests again demonstrated the importance and the remark-
able efficiency of a smoke vent over the stage, of about 11 per cent, of its area.

It is of interest to note that these two sets of Austrian experiments have
given a complete answer to two of the puzzling questions of the fire at the Ring
Theatre. At the inquest the man was sought who was supposed to have turned
off the gas from fear of an explosion, thus leaving the house in darkness while the
audience and actors were struggling to escape; he was not found. Both series of
these experiments on the theater models show that a back pressure of air in the
auditorium more than sufficient to force the gas back in the pipes, and thus
extinguish the lights, was produced by the rapid expansion of the air over the
stage due to the heat of the fire. Indeed, this quick back pressure was found suf-
ficient to account for the bursting open of the large scene door at the back, which
it had been supposed was opened inadvisedly, thereby causing the draft which
blew the suffocating smoke into the auditorium.

I have not the full report of these later tests at hand. In studying the reports
of the Austrian tests of 1885, I am unable to believe that the back pressures due
to expansion of air are ever likely to be so large in an actual theater fire as those
developed in the model tests and carefully measured on the manometers. I saw
no evidence of so great pressures at the Iroquois, and failed to find evidence in
the testimony of the eye-witnesses, although the conditions were favorable for
very rapid burning. I have no doubt there may have been sufficient pressure
momentarily, at the end of the first half-minute or full minute, to blow the
curtain strongly outward, but the absence of scorching of wood and textiles
around the opened rear stage door shows conclusively that after this was opened
the air current there was continuously inward.

In the Austrian experiments of 1885, with smoke vents closed, air pressures
were developed momentarily at from 20 to 30 seconds after lighting the tire as
great as ^ Ib. per square inch, or equivalent to 5 or 7 inches of water column or
33 to 38 Ibs. per square foot ! With smoke vents covered by thin paper which
quickly burned open the excess of air pressure on the stage was only momentarily
equivalent to 0.07 inch of water column, with no excess observed in the auditorium.

The preliminary reports of the Austrian experiments of 1905 show that with
smoke vents closed, even a steel proscenium curtain was no sufficient safeguard
for the audience. The air pressure due to expansion held it from lowering
promptly, and when lowered the suffocating gas and flames were driven past its
loosely fitting edges into the auditorium. With smoke vents open a proscenium
curtain was hardly necessary.



practical and successful, as proved by years of use. They can be
obtained from any of the manufacturers of automatic sprinklers.

It is strange almost beyond belief IIOAV slowly and scantily these
have found their way into the fire protection of theaters.

These links melt open at about one hundred and sixty-two de-

Closed Open,


Closed Opening


Closed Open



grees Fahrenheit, and thus will open long before flame reaches them.
Their cost is trifling. They are stamped out of sheet brass,
soldered with " fusible solder," the formula for the 162 F.'alloy

Tin 12 per cent.

Lead 25 " "

Bismuth 50 "

Cadmium 13

Total.. 100 " "


Links like those shown in Fig. 4, tested to immediate rupture,
will break under a load of about two hundred to five hundred
pounds, but can be trusted to sustain continuously a load of
only about fifty to one hundred pounds. Our tests show that
the solder becomes somewhat weaker in warm air than in cool
air. Probably in an atmosphere of 100 F. the links would safely
sustain 10 per cent, to 20 per cent, less load than in an atmos-
phere at 60 to 70 F.

All of the known solders that fuse at low temperature are
subject to stretching or "cold flow" under long-continued
loads, unless these loads are made extremely small, and one of
the most important features in the design of any such link is to
make the direct stress upon the solder small and in tension over
a large area, rather than by shear.

The links shown in Fig. 4 will open with about the same
promptness as an automatic sprinkler. In a test oven, immersed
in an atmosphere of four hundred degrees Fahrenheit, these vari-
ous forms of link open in 35 to 100 seconds ; in five hundred de-
grees, in 25 to 75 seconds.

At top of rigging loft over a fire like that on the Iroquois
stage, fusible links probably would open within 30 to 60 seconds
after the blaze got a good start, and in ample time before the
smoke would burst out under the proscenium arch. There is
ample space in the hanging loft to pocket the smoke for the
first minute or two. At the Iroquois fire statements of eye-
witnesses indicate that it was probably fully two minutes before
the smoke rolled out into the auditorium. I was surprised to
find on measurement of the Iroquois plans that the volume of
air space above the level of the arch was greater over the stage
than over the auditorium.

The sensitiveness of these links or their quickness of action under
moderate degrees of heat depends on the thinness of the mass of
metal to be warmed up, and therefore on the rapidity with which
it absorbs heat enough to melt the solder. These two character-
istics the weakness of the fusible solder under long-continued
strain, and the necessity for rapid absorption of heat, limit the
size and strength of fusible link that can be employed; but it is
easy to so design the connections that the strain will be about fifty
pounds, thus large enough to override dust, rust and petty de-
rangements and small enough to be within the capacity of the
fusible link. In many situations a link is desired of such form


and size that when inserted in a rope it can run over the ordi-
nary pulley.

Imperfections of Smoke-Vent Design.

Concerning the design of smoke vents, those that I have seen
in actual use have been, with hardly an exception, imperfect pieces
of mechanical design. At certain of the most recent New York
theaters I have found the type which appears to be the favorite
for meeting the New York building law, set with such a clearance
as to give a very unnecessary degree of ventilation, which tempts
the theater mechanic to stop the draft by some means that may
prove dangerous. It is, moreover, so heavy and unwieldy that
it cannot be frequently tested by opening and closing, and to
wait for the burning of a hempen cord to open a device of this
kind should be regarded as criminal negligence when it can be
done so much better and quicker by the automatic fusible link.

Smoke-Vent Designs by the Author.

To meet the proper suggestion that one should not merely criti-
cise without presenting a better device, and as a means of illus-
trating that the problem can be solved along various lines of
design, I have worked out two models, shown in the accompanying
drawings. I am certain that with the experience to be gained in
constructing one after another, these designs could be improved
upon. It is desirable that the total smoke-vent area of one-
eighth or one-tenth the stage be subdivided into four independent
units for convenience in size and for the further safeguard that
should one stick there are three others left.

The fundamental requirements for a theatre smoke vent are :

1st. Absolute certainty of opening by force of gravity, in
spite of neglect, rust, dirt, frost, snow, or expansion by heat,
twisting or warping of the framework.

2d. Quickness of opening to be secured by automatic links
of the thinnest metal practicable, and also by controlling the
doors by a cord run down to the prompter's stand and to the
station of the stage fire-guard.

3d. Simplicity and massiveness of the operative mechanism
of the smoke vent. This should be designed not as a watch-
maker would build it, but more according to the standards of
railroad service or rolling-mill practice. The counterpoise
weights should be heavy, and a constant tension on the re-



lease cord of upward of thirty or forty pounds so that rust,
cobwebs or temperature changes may not be of noticeable
effect in the resistance to be overcome-

4th. Daily Tests. It should be of such form that it can be
tested daily, or at least at the weekly inspection, by partially
opening it, preferably closing it again by means of the cord
running to the prompter's stand. It may perhaps add to the
safety if it is of such design that it can be used whenever
needed for the ordinary ventilation of the stage, summer or
winter, rain or shine, thereby keeping it under constant view
and bringing into immediate notice any difficulty about its
opening or lack of repair.

In the first of these designs submitted, shown in Figs. 5, 5a, 5b,


FIG. 5.


5c, 5d, the opening, eight by twelve and one-half feet, of which
four would be needed over the stage of ordinary size, has a roof
for protection from rain and has vertical sides that contain foui
small windows for admitting abundant daylight to the rigging
loft, but which can be closed by ordinary window shades for dark
scenes. All necessity for the wire screen is avoided. The ver-
tical shaft may well be three to five feet taller than shown. The
four shutters fall outward lest the pressure of the updraft tend to
hold them shut, and are pulled open ly force of gravity, opening
to the full area called for. The pull on the rope holds them



against their seat, which, if made with a thin edge pressing
loosely against fibrous material, as shown, will be more tight
against cold-air drafts than a common window sash or house door.
Fusible links are inserted in each of the four branches of the

Area of Shaft 8' x 12' 0" 100 Sq. 1< t .
Area of Shutter Opening Same





cord. No sprinkler should be placed up within the monitor con-
taining these links, lest perchance the sprinkler open first and
chill the links, and care should be taken that the links are of a
thin, quickly sensitive type.



In the second design, Fig. 6, the sliding type is used. This
obviously cannot be used as an ordinary ventilator in rainy days.

felt packing,
of angle iron.

FIG. 5c.

For adflitional L
weights ^\


FIG. 5D.

The special effort in remodeling this from the current New York
type has been, first, to place the glass in the vertical side so that
no necessity remains for a wire screen to catch any broken glass.





Sheet Copper
fWeather Guard



J I ^

( )

*^> '"^\ \


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Online LibraryJohn Ripley FreemanOn the safeguarding of life in theaters; being a study from the standpoint of an engineer → online text (page 2 of 8)