August 14, 1914.

The colliery guardian.

^65

by passing it through sodium potassium peroxide, which
has the property of not only taking up carbon dioxide
and moisture from the expired air, but also of liberating
oxygen in quantity sufficient to replace the oxygen
absorbed in respiration. The expired air passes by a
wide flexible tube of metal to a double cartridge on the
bag, and thence on to a bag carried behind. The
inspired air returns by the same passages. There are
two double cartridges with a flexible tube leading to
each, so arranged that when one cartridge is exhausted
the breathing can be switched on to the second.

From the tests it was quite evident that the design,
excellent as it is in principle, has never been properly
worked out in relation to mining conditions. The
present apparatus would, it seems to me, be very
dangerous to use for purposes of rescue or other serious
work in poisonous air.

General Remarks on Self-contained Apparatus.

Without repeating the general remarks at the end of
the previous report, I may now refer to the conclusions
to be drawn from the present series.

In the first place, there has been very marked improve-
ment in several forms of the apparatus, and. the
publication of the previous report seems to have been
of great benefit in this respect. Both mine managers
and makers of apparatus had. been placed in a somewhat
difficult position by. recent legislation. On the one
hand, almost any apparatus, however unsafe it might
actually be, would fulfil the requirements of the Act.
On the other hand, no mine manager worthy of British
traditions would feel justified in risking the lives of his
men with apparatus only guaranteed by the statements
of makers—statements which, as both the previous and
the present report have shown, are sometimes extremely
misleading. The makers of well designed and carefully
tested apparatus were also placed at a disadvantage,
which was entirely contrary to the interests of safety.

Of the designs submitted for test in the present series,
two gave bad results. The Pneumatogen, which had.
not been tested before, proved defective, although there
seemed to be no reason why the defects noted could
not, by altering the design, be remedied. The Meco
gave unsatisfactory results, owing to the unreliability
of the purifier. This also can be remedied, although
other disadvantages would still remain, unless they,
also, were remedied.

Of the remaining designs, the liquid air apparatus of
the Durham and Northumberland rescue stations passed
the tests satisfactorily, and was an immense improve-
ment on the liquid air apparatus dealt with in the
previous report. The other liquid air apparatus was
also much improved, but broke down in one point where
it differed from the Durham and Northumberland
apparatus. I am still of opinion, for the reasons given
in the previous report, that both in regard to conveni-
ence and adaptability to mining conditions, the liquid
air principle is inferior to the use of oxygen cylinders.
The tests in hot air indicated, also, that very little
advantage was derived from the coolness of the air.
A safely constructed liquid air apparatus weighs just
as much as an oxygen cylinder apparatus.

The Drager apparatus has been, I think, very greatly
improved by making its action independent of the
injector, and by providing a better purifier. The purifier
actually submitted was not quite sufficient to fulfil the
tests completely, but this was known to the makers,
who undertook to prepare a somewhat larger one shortly.
The new purifer also proved defective in hot air above
the body temperature. In the apparatus submitted no
change had been made with a view to protecting more
efficiently the parts carried on the shoulders, but there
was a very good arrangement for preventing the
accidental turning of the main valve of the cylinder.

In the Weg apparatus the improvements have been
very striking. The resistance to breathing and liability
to leakage have been greatly reduced, and the apparatus
came very successfully through the final tests. The
pressure in the bag of both the Weg and liquid air
apparatus is somewhat high, and this has caused me
some misgiving in two respects. An accidental leak
developing in the Weg apparatus in its present form
might apparently give rise to a rather rapid and possibly
dangerous waste of oxygen. The apparatus, including
the bag, is, on the other hand, very strongly made and
well protected. During rest, however, the pressure
rises so high as to cause some leakage outwards from
the mouthpiece. Small leaks would not matter in the
liquid air apparatus, in which the pressure is also high.
The other cause of misgiving is the fact that it is known
from animal experiments that with a positive pressure
of as little as 2 in. of water air begins to leak out from
the lungs into the neighbouring cavities and tissues,
and is said to gain access also to the blood in the form
of small bubbles, and to be thus liable to cause air
embolism. This matter requires further investigation,
and I intended to make some further experiments upon
it on animals, but have not as yet succeeded in obtaining
the necessary licence from the Home Secretary. It
seemed a possibility that the otherwise unexplained
giddiness, etc., experienced in one of the liquid air
experiments, was due to this cause. The automatic
governing of the oxygen supply of the Weg apparatus
seemed to be nearly perfect during work, but there was
waste of oxygen at the mouthpiece during rest, owing
to the pressure. Even so, the oxygen lasted much
longer than with an apparatus adjusted to give a con-
stant supply of two litres a minute.

The Proto apparatus was also considerably improved
by the addition of the metal cooler, and by strengthening
one or two rather weak connections. This cooler
seemed strong enough for use underground, but it is
nevertheless somewhat clumsy. It gave results which
were apparently sufficiently good to prevent a man from
being disabled by the heat of the inspired air before he
was disabled by rise of his body temperature. The
Proto apparatus was formerly inferior to some other
apparatus in this respect, but with the metallic cooler

gave nearly as good results in hot air as the liquid air
apparatus, and at air temperatures above that of the
body seemed definitely better than the Drager, and
was fully equal to the Weg. With the sodium sulphate
cooler the Proto gave much better results in hot air than
any of the other apparatus.

Smoke Helmets and Masks.

In addition to experiments with self-contained fescue
apparatus, a number of experiments have been made
with smoke helmets or masks supplied with air through
a flexible pipe by a bellows or pump. The limitations
of an apparatus of this kind are evident. It is difficult
for a man to take in with him more than 60 or 70 yds.
of pipe. It he wears a complete helmet his vision is
limited, and his hearing rendered almost useless, parti-
cularly as the air entering the helmet is noisy. Linder
an insecure roof he would, therefore, be specially
exposed to danger. On the other hand, the working of
the apparatus is very simple, and as a matter of fact
smoke helmets have often done very good work at
underground fires.

In most cases a self-contained apparatus would be
preferable, provided a trained man were available; but
for very hot and moist atmospheres, such as are met
with frequently in dealing with spontaneous fires or
heatings underground, there may be definite advantages
in a smoke helmet. The limitations of a self-contained
apparatus where the wet bulb temperature exceeds
about 80 degs. Fahr, are evident enough from the
experiments already described. In proportion as the
wet bulb temperature rises above about 80 degs. Fahr.,
the period during which hard work is possible in a warm
and still atmosphere becomes more and more restricted,
since sufficient heat cannot be got rid of from the skin
to balance the heat produced in the body.

With a smoke helmet and good air supply, the wearer
is supplied with air which, though it may have become
fairly hot in its passage through the pipe, is nevertheless
dry. With a self-contained apparatus dry air would also
be furnished for a considerable time; but only as much
air as the wearer breathed would be available for cooling
the body, and the cooling effect would be trifling. With
the smoke helmet the air not only circulates over the
head, but, if the coat is buttoned up properly over the
leather flap of the helmet, passes down over the body
and exercises a powerful cooling effect, which depends,
of course, on the amount of air supplied. This effect
can be realised if, when wearing a smoke helmet in air
with the wet bulb temperature at about 110 degs. Fahr,
or more, one puts the hand beneath the coat. The
feeling of coolness is very striking.

A few experiments have been made in order to test
the action of an ordinary smoke helmet worked by hand
or foot bellows, of which several were sent for trial by
Messrs. Siebe, Gorman and Company Limited.

With the wet bulb temperature a little low^er shan
110 degs. Fahr, a fair amount of work could probably
be done for a short time with a smoke helmet provided
with bellows supply. The limitation of the air supply
greatly reduces the utility of the smoke helmet, how’-
ever. Far more air than is needed for respiration can
easily be obtained, but the quantity needed for cooling
is, of course, a very different matter, as simple calcula-
tions easily show.

With good impervious clothing, and a proper supply
of the very dry air furnished by the compressed air
mains of a mine, there is no doubt that a man with a
smoke helmet could work in atmospheres where ordinary
self-contained apparatus would be useless, and where
work without apparatus would be equally out of the
question.

Besides testing smoke helmets, we made some obser-
vations with a mask supplied with air in the same way
as a smoke helmet. The mask tested was provided with
an inlet opening, with non-return valve for the air
supply, and an outlet opening, with non-return valve for
the expired air, and for the excess of air supplied. The
pattern of mask was the same as that of the Fire
Brigade modification of the Proto apparatus (referred to
in the’ previous report). With a hand bellows the
amount of air needed during the work could be sup-
plied with ease through 200 ft. of the tubing, the
breathing being quite comfortable. When the pumping
was purposely stopped, the wearer, to my considerable
surprise, could still obtain enough of air through the
tube, so that he was not at the mercy of the man who
was pumping. The resistance to inspiration was, of
course, considerable under the circumstances, but
sufficient air came through the bellows and tube. When
the inspiratory tube was blocked, no air leaked in, or
hardly any. With the ordinary smoke helmet the
wearer is dependent on the man pumping. Reference
has already been made io the satisfactory behaviour of
the mask when used in connection with the self-
contained apparatus, and I was considerably impressed
with it when used with an air pipe. It would pro-
bably be very useful in work with the head in high
places filled with firedamp or fumes, as a piece of pipe
8 or 10 ft. long could be left with its end in good air
below, while the wearer was working above. No pump
would be needed. The fact that the ears are quite free
with the mask, is, in my opinion, a great advantage
and source of additional safety; and although the mask
is inferior to the helmet in great heat, it seems to me
safer and much more likely to be often used with success
than the helmet.

Equipment of the Doncaster Rescue Station.

I have been asked by the committee to offer an
opinion as to the most suitable apparatus for the
special requirements of the Doncaster rescue station.
In the present rapid state of development in the
efficiency of self-contained apparatus it would be use-
less to offer any opinion as to which form will develop
into the best apparatus finally, for it is quite clear
that all can be improved.

Apart from the serious capital and other expenses of

the liquid air system, I do not think it would prove so
reliable, or be so quickly and conveniently available as
the oxygen cylinder method. In view of the results of
the tests, this conclusion seems to limit the choice at
present to the Proto, Weg, or Drager apparatus. Each
of these, in the newest form, is good, and each has its
own advantages. I think, however, that in view of
the experiments the Drager would give out much
sooner in the work of dealing with underground fires
in hot atmospheres. It also seems more liable to
injury against the roof.

It appears quite likely that the distinctive principle
of the Weg apparatus will prove superior to the con-
stant supply principle. At present, however, the regu-
lation of the oxygen supply has not given better results
than can be obtained by arranging for a constant supply
variable within certain limits, as in the Proto
apparatus. Against the advantages of the automatic
governing in the Weg, there exists some, doubt as to
whether the automatic regulator may not be liable to
get out of order, and whether the risks of accidental
leaks outwards, and the physiological disadvantages
associated with the positive pressure inside the
apparatus are not serious. These points can only be
decided by further tests and practical experience.

The Proto is the simplest of all the apparatus. As
the shoulders are clear, it is less exposed to injury
against a low roof, and nearly all the vital parts are
under the direct observation of the wearer. When
provided with a sodium sulphate cooler, it is at present
much the best apparatus for work in hot air. The
breathing is more free than with any other apparatus,
and the apparatus responds easily to any temporary
exertion of an unusual kind. The by-pass provides
for an extra supply of oxygen whenever this is needed,
and is convenient for starting the apparatus, besides
being a resource to fall back on if through some acci-
dent the ordinary oxygen nozzle became blocked. Of
the apparatus available it is 'the one in which I should
for the present feel most confidence if I had to go a
long way into poisonous or irrespirable air, or to work
in hot air; and while I am well aware that there may
be room for differences in opinion, I think it is on the
whole the best apparatus for the equipment of the
Doncaster rescue station.

The wide tubes and valves of the London Fire
Brigade pattern ought, I think, to be adopted, as well
as a sodium sulphate cooler, and probably also a regu-
lating arrangement to enable the oxygen supply to be
cut down from 2 litres to as little as about 0-5 litre, in
case of a man having to rest in irrespirable air, or to
be left behind for an hour or more.

If the rescue station committee should decide on the
Proto, I think that further experiments, both above
ground and underground should be made, in order to
decide on certain details, such as the best and cheapest
form of absorbent, the means for regulating the oxygen
supply, and whether an automatic blow-off valve is
desirable. The rules and organisation in connection
with the use of the apparatus w’ould also have to be
settled, as well as the course of training for the men
belonging to the brigade. Far more thorough, scientific
and searching training and selection of men than has
hitherto been usual would, in my opinion, be desir-
able, and the stations ought to be so equipped as to
make this training possible under conditions which, as
regards muscular work, heat, smoke, poisonous air,
and other adverse conditions, would be worse than those
ever likely to be met with underground. This would
teach the men to know the apparatus thoroughly, and
to be ready to deal coolly and intelligently with difficult
situations.

If records of all points of importance in connection
with the working of the apparatus were kept by the
superintendent, I think these records would prove of
great value.

I may perhaps point out that the connection between
the Doncaster Coal Owners’ Research Laboratory and
the rescue station will make it possible to allow the
gradual perfection of apparatus, training, and organi-
sation to progress hand in hand with scientific
investigation of each point as it arises, and probably
to avoid a good deal of useless waste of energy and
money. It w’ould be well to obtain for the station
samples of improved apparatus of other types than
the Proto, as they become available, so as to keep in
touch with other stations, and with all important
improvements.

THE ROSEHALL SIGNAL INDICATOR *

By James Black.

The Rosehall signal indicator is essentially different
both in construction and in action from any other indi-
cator which has come under the writer’s notice; and he
believes it to be at the present moment the only
indicator which complies with the Home Office require-
ments. The outstanding features of this indicator are
as follow :—

(1)	Any number of levels or hanging-on places may
be worked with only one instrument, as the level from
which a signal is given is indicated simultaneously with
the signal.

(2)	It indicates the proper signal and shows the nature
of the signal.

(3)	A signal may be repeated as often as is desired.

(4)	Its employment does not necessitate any altera-
tion on the ordinary wire and hammer signalling
arrangement commonly in use.

(5)	It is very compact, strong, durable, and reliable.

The instrument is so designed as to give visual indi-
cation to the winding engineman of the number and
nature of the signals given. Provision is also made for

* From a paper read before the Mining Institute of Scot-
land, August 8, 1914.