364

THE COLLIERY GUARDIAN.

August 14, 1914.

Self-contained Rescue Apparatus and Smoke Helmets.*
SECOND REPORT OF DONCASTER COMMITTEE.

By J. S. HALDANE, M.D., F.R.S.t

In the previous report on self-contained rescue
apparatus,^ it was shown by experimental tests that a
number of serious defects existed in forms of rescue
apparatus at that time in use. As, however, these
defects appeared to . be more or less remediable,
arrangements were made for a second series of tests,
after an interval of four months, so as to give time
for the introduction of improvements. For this second
series improved or altered forms of apparatus were sub-
mitted by makers or users. The latest form of
Pneumatogen apparatus was also submitted for trial
this apparatus not having been tested in the first series.
The present report deals with the results of these further
tests, and of some experiments with smoke helmets.

As before, Messrs. T. F. Winmill and J. Ivon
Graham have co-operated with me, and invaluable help
has been given by Mr. Macaskill, superintendent of the
new Doncaster rescue station; and Mr. Geoffrey
Phillips, of Bentley Colliery. Mr. Clive and others
have also given every help, as well as several gentle-
men who came to the laboratory in charge of apparatus.

Apart from tests in hot air, the methods used in the
present series of experiments were for the most part
similar to those in the former series, and the improved
apparatus tested will be referred to in the same order
as in the former report. §

Proto Apparatus.

The main defect previously noted in this* * * § apparatus
was that in a warm atmosphere the air coming from
the purifier becomes too hot to breathe after about an
hour or more. Thus, at a temperature of 94 degs.
Fahr, the wearer was stopped by the hot air after walk-
ing for hours. To overcome this difficulty, the
makers supplied a metal cooler, which can be fitted on
the top of the bag. Two or three patterns were sub-
mitted, but the most effective one consisted of a stout
metal tube bent three times on itself and firmly
attached to each side of the metal top of the bag. This
arrangement was tested in the hot room, with the
temperature at 111 degs. Fahr., and the wet bulb at
71 degs. The work was stopped in this experiment,
and subsequent ones with the same cooler, on account
of exhaustion associated with rise of body tempera-
ture, and not because of the inspired air becoming hot.

Although the main defect of the Proto apparatus had
been removed by the addition of the cooler, the latter
is a somewhat clumsy addition, and there remained
the defect that after a time the heat of the bag passed
through the asbestos apron covering the abdomen of the
wearer, and became uncomfortable. The rise of body
temperature appeared to be partly due to the heat from
the bag, in which temperatures as high as 210 degs.
Fahr, were observed in long experiments.

The rise in temperature in the bag could evidently
be dealt with by increasing the charge of soda. This,
however, was a clumsy and expensive expedient. A
trial was therefore made of the plan of placing in the
inspiratory bag a smaller rubber bag (a small foot
warmer) filled with caustic soda sticks and closed up :
the object of this smaller bag being simply to absorb
heat. This plan was not very successful, so it was
decided to fill the smaller bag with a salt which melted
when warmed, and absorbed a large amount of heat in
the process of melting. It was not desirable to use any
salt which would cause danger in the event of the
small bag becoming leaky, and Mr. Winmill suggested
ordinary sodium sulphate as the most suitable salt. It
was found that no heating is produced if sodium sul-
phate is mixed with caustic soda, and, of course, no
fumes are given off. Sodium sulphate melts at 90 degs.
Fahr., and the temperature remains steady at 90 degs.
Fahr, until all the sodium sulphate is melted. It was
found, however, that the small bag did not absorb heat
quickly enough. It was still quite cool, with the
sodium sulphate mostly unmelted, at the end of a long
experiment, and hot air was passing it without being
sufficiently cooled.

I then asked the makers of the apparatus to supply
a breathing bag with three, instead of two, compart-
ments, the compartment next to the wearer being com-
pletely shut off from the two breathing compartments,
and being intended to hold the sodium sulphate. With
this arrangement the sodium sulphate not only cooled
the inspiratory (middle) compartment of the breathing
bag, but also the caustic soda in this compartment.
The wearer was also completely protected against
heat passing through the asbestos apron to his abdomen.

A first trial was made in the hot chamber, with 2 lb.
of sodium sulphate in the cooling compartment, and
61b. of an absorbent consisting of coke saturated with
a very concentrated solution of soda. (supplied by the
makers). Unfortunately, the weather was very hot
and close; and although the temperature of the chamber
was only raised to 108 degs. Fahr., the wet bulb
temperature was as high as 84 degs. The result was
very favourable, so far as it went, although the high
wet bulb temperature had cut short the experiment by
causing a rise of body temperature. The sodium sul-
phate had completely fulfilled its purpose, and was not
nearly spent.

* From the Second Report to the Doncaster Coal Owners’
Committee (Gob-fire Research) on Self-contained Rescue
Apparatus and Smoke Helmets.

f Director of the Doncaster Coal Owners’ Laboratory.

+ See Colliery Guardian, January 23, 1914, p. 201.

§ Dr. Haldane prefaces his report with some valuable
observations on the effect of heat, which will be given next
week.

A further experiment was made in the large power-
house of the colliery, where, as the weather was very
hot, the temperature was 100 degs. Fahr., and the wet
bulb 81 degs. Mr. Macaskill walked up and down at
four miles an hour, the bag being charged with 5 lb.
of caustic soda sticks, and 2 lb. of sodium sulphate in
the back compartment. The front compartment soon
became very hot, but both the inspired air and the back
of the bag remained perfectly cool, and comfortable.
At the end of one hour and 40 minutes the experiment
was brought to an end by the bursting of a seam in
the back compartment. This seam was quite weak, as
the back compartment had only been temporarily
arranged for experimental purposes. At the time when
the burst occurred, the sodium sulphate had completely
melted, and the temperature of the solution was begin-
ning to rise, and was about 105 degs. Fahr. After 1J
hours, the mouth temperature was 100-5 degs., which
was remarkably low, considering the wet bulb tempera-
ture of 81 degs. This experiment showed that the
sodium sulphate was completely successful in
neutralising the heat from the purifier. The same
sodium sulphate can, of course, be used over and over
again.

With regard to the weak connection previously noted
in the Proto apparatus, this oad been strengthened in
the new pattern, and appeared to be satisfactory.

Weg Apparatus.

In the previous report it was noted that the resist-
ance to breathing in the Weg apparatus was excessive,
and that much leakage both inwards and outwards was
apt to occur at the face piece. An improved apparatus
was submitted in which these defects are remedied. A
mouthpiece is substituted for the face piece, and wide
flexible breathing tubes pass over the shoulders of the
wearer to the purifier, which is arranged so as to give
very little resistance. The reducing valve is also so
arranged that it begins to open if the pressure in the
apparatus falls below 3 in. of water, and opens freely if
there is no pressure. The mouthpiece and breathing
tubes actually submitted were somewhat large and
clumsy, but this defect could easily be remedied, and
did not affect the tests.

The tests show a very great improvement in the Weg
apparatus since the last series. The apparatus is much
safer and less liable to leakage inwards or outwards, and
the purifier is extremely efficient and free from
resistance.

Drager Apparatus.

The main criticisms of the former forms of this
apparatus were : (1) That the helmet was dangerous,
for reasons fully explained; (2) that the injector was
liable to get out of order unless great care was exercised;
and (3) that the purifier was inadequate in size, and
thus a source of danger. •

A new form of the apparatus was submitted, and
Herr Bernhard Drager kindly came to explain the
alterations, and was himself present at the first tests.
He explained that there had not been time to carry
out all the contemplated alterations completely, and
that further experiments were in progress at the Lubeck
works. In particular, a large purifier was being pre-
pared.

The alterations in the apparatus submitted were as
follows :—

(1)	A short pipe was added, with non-return valve,
so that the air could circulate through the purifier even
though the injector was not working at all. The direct
communication between the inspiratory and expiratory
bag was also abolished, so as to enable the lungs to
drive the air through the purifier independently of the
injector. The blow-off valve was regulated so as to
give the pressure required for this.

(2)	An arrangement was added to make it possible
to obtain a supply of oxygen in the event of the oxygen
nozzle of the injector becoming accidentally blocked.

(3)	A purifier containing more caustic soda than the
old one was supplied.

(4)	A very neat and effective arrangement was added
to prevent the main valve of the oxygen cylinder from
being accidentally turned off. In other respects the
apparatus was not altered.

From the tests it appears that in the new form of
Drager apparatus the wearer is no longer dependent on
the injector, and however hard he breathes, can always
rely on having pure air to breathe, so long as the
purifier is not used up. This is, to my mind, a very
great improvement. The new purifier lasted for a
considerably longer time than the old one, but was
still not adequate to fulfil the conditions specified in
the first report as desirable. It was also inadequate
to retain moisture in a hot atmosphere, so that the
apparatus would soon be put out of action in an atmo-
sphere above body temperature, unless the purifier was
frequently changed—an operation which can be per-
formed easily with the Drager apparatus, but which
would cause much inconvenience.

Meco Apparatus.

A modified form of this apparatus was submitted by
the makers. The chief alterations were : (1) That a
good protecting cover was introduced for the parts of
the apparatus on the back; and (2) that two injector
nozzles were arranged, so that in the event of one being
disabled the other could be brought into action. The
oxygen supply could also be regulated to 1, 2, or 3 litres
per minute.

With 2 and 3 litres of oxygen a minute the average
air circulations were 38-5 and 47 litres a minute. The

latter air supply would have been sufficient but for the
absence of valves or failure of the purifier. It is pro-
bable that both causes contributed to the unfavourable
result.

After the failure of the new double injector type the
makers submitted an apparatus with the old type of
injector. On reference to the first report it will be
seen that this apparatus behaved very well in a dura-
tion test. Only one such test was made, however. An
equally good result was expected on testing the
apparatus now submitted. In the experiment recorded
in the first report the particular purifier used had acted
all right, and I refrained from criticising it, although
its internal arrangement was not much liked. The
present experiences have shown that it is unreliable.
It is well to point out clearly that the consequences of
a purifier breaking down at some distance from fresh
air might be extremely serious, and that a form of
purifier which sometimes acts well and sometimes fails
is particularly dangerous.

No tests were made wTith this apparatus in hot air,
as they could hardly have been of much use. Negative
pressures were observed in the purifier circuit. This is
due to the position of the injector, and is not a very
desirable feature of the apparatus.

Liquid Air Apparatus.

There were so many sources of danger in the liquid
air apparatus submitted for the previous set of tests
that it wrould have been extremely risky to venture
with it into poisonous air. Through the courtesy of
Col. W. C. Blackett, arrangements were made for test-
ing the improved apparatus recently introduced at the
Durham and Northumberland collieries fire and rescue
stations. Mr. F. P. Mills, superintendent of the
stations, who had worked out the more recent improve-
ments, assisted at the tests, bringing with him two
members of his brigade in order to help; and Col.
Blackett was also present on one day.

The apparatus is furnished with a mouthpiece and
nose clip, inspiratory and expiratory tubes of ample
diameter, a blow-off valve on the expiratory tube, a
stout air bag, and a purifier of ample size contained coke
soaked in caustic soda solution, with some sticks of
caustic soda beyond the coke. When fully charged
with 8| lb. of liquid air, the apparatus weighed
40 lb. 2 oz.

The rise of body temperature was about 0’8 deg.
Fahr, more than in the corresponding experiment where
no apparatus was worn, about 0*4 deg. less than when
the Proto apparatus with metal cooler was worn, and
0’7 deg. more than with the Proto with sodium cooler
and a wet bulb of 81 degs. Fahr. (8 degs higher). The
advantage due to the low temperature at which the air
issues from the container was thus not as great as might
be supposed. In air with a very high wet bulb tempera-
ture the liquid air apparatus would certainly continue
to give breathable air for as long as the purifier lasted,
but the Proto apparatus with sodium sulphate cooler
would also do this, and at the same time give a less rise
of body temperature.

It is clear that the Durham and Northumberland
apparatus is far safer and more reliable than the liquid
air apparatus tried in the former series of tests, and
represents the first really successful application of the
liquid air principle to mining requirements.

In addition to the Durham and Northumberland
apparatus, a liquid air apparatus was also submitted by
the Liquid Air and Rescue Syndicate Limited. In
general arrangement it was similar to the Durham and
Northumberland apparatus, but it was about 41b.
lighter, and the resistance due to tubes, valves, etc.,
was greater. The purifier contained 2 lb. of granulated
caustic soda, and the blow-off valve was set to blow
off at 3 in. of water pressure.

During walking at a moderate pace the apparatus gave
no trouble, but shortly after the pace had been quickened
up the bag emptied itself through the blow’-off valve,
and there was consequently no air to breathe. The
blow-off valve was then re-set to blow off at 6 in. of
water pressure, but the bag again blew off when I
walked at a good pace. Mr. Phillips then put on the
apparatus, without altering the blowr-off valve, but found
the resistance too great for walking at four miles an
hour. The valve wras then re-set to the former pressure,
and Mr. Phillips walked at four miles an hour without
trouble. On increasing his pace, however, the bag
emptied itself through the blow-off valve. The result
was the same when he ran for a short distance.

The reason for the emptying of the bag was that the
resistance between the mouthpiece and the bag was
far too great when the breathing was much increased.
As a consequence, the pressure during expiration went
above the pressure at which the valve was set. An
actual measurement gave about 14 in. of water pressure
during expiration. Emptying of the bag would be a
very dangerous occurrence in an irrespirable atmosphere
underground. To prevent this accident and reduce the
labour of breathing, wider valves and tubes between the
mouthpiece and the bag are needed. The blow-off valve
might also be placed elsewhere than on the expiratory
tube. The latter plan would throw a little additional
work on the purifier, but would remove a source of
serious anxiety. The action of the purifier itself was
none too good, and would depend on the care with
which each purifier had been filled.

The supply of liquid air from the container tested was
satisfactory. Before actual use in dangerous atmo-
spheres, it would be wise to test each liquid air container
separately and to repeat the tests at intervals, as the
heat insulation might vary, owing to condensation of
moisture in the insulating material or other causes.

Pneumatogen Apparatus.

A Pneumatogen apparatus of the latest type, with
the purifier carried on the back, was submitted for test
by Mr. Richard Cremer, of Leeds, the agent for the
apparatus. In this apparatus, invented by Profs.
Bamberger and Bock, of Vienna, the air is regenerated