September 13, 1918. THE COLLIERY GUARDIAN. 549 ratory tube, would be dangerous in that it might be the cause of the oxygen supply failing. How apparatus may be tested for leakage before it is put on is described later. When testing, attention should be directed in particular to those parts subject to negative pressure—namely, the mouthpiece and inspiratory tubes. It is important for rescue men to realise the special danger of a leak inwards when the air contains carbon monoxide (afterdamp and gas from fires or spontaneous heating of coal). The carbon monoxide is gradually absorbed by the blood until its power of carrying oxygen is seriously diminished. The effect of this may not be noticeable so long as a man is doing little work, and particularly if there is nearly pure oxygen in the breathing bag; since when nearly pure oxygen is breathed the blood carries much oxygen in simple solution, independently of the carrying power (due to haemoglobin) which is weakened by the carbon Map showing the Positions of Central Mine Rescue Stations and Sub-stations. (Circles.= 10 miles radius.) D'QDLt ■RFORO monoxide. But as soon as the man begins to exert himself seriously, as in ascending an incline, he requires all the normal oxygen-carrying power of his blood, and if this is much impaired by carbon monoxide he is apt to faint owing to insufficient oxygen supply to the heart. This liability is largely increased if the oxygen ] ercentage in the bag diminishes, owing to the oxygen supply being insufficient to meet the in< reased demand, and also to the simultaneous presence inside the bag of nitrogen which has leaked in along with the carbon monoxide, or has accumulated owing to the oxygen in the cylinder being impure. The danger can be averted by going slowly; and a young and active man is more likely to be affected in this way than an older m in, who is less apt to hurry. But the main point is to be most careful to avoid the leakage. A leaky mouthpiece is specially dangerous; and many lives have probably been lost owing to the use of helmets or face pieces, and consequent leakage inward as well as outward. Treatment of Person Suffering* from CO Poisoning*. The correct treatment of a person who has collapsed from carbon monoxide is to restore the noseclip and mouthpiece, and having made sure that the apparatus is working satisfactorily, flush out the breathing bag with oxygen. In brief, collapse from CO poisoning while wearing a leaky rescue apparatus is particularly apt to happen during a-*ce erating muscular exertion, and the only treatment likely to be attended with success is to keep the patient breathing as pure oxygen as possible until he has been removed to innocuous air, and for some time after he regains consciousness. Oxygen apparatus should also be at hand for a long while after- wards, ready to be applied if unconsciousness should again supervene; and the patient must be kept warm all the time. 5. Failure due to Flattening of 'Breathing Bag.—The inspiratory breathing bag may become so empty that a full breath cannot be drawn from it. This is in practice a dangerous accident if it occurs suddenly, and has probably been the indirect cause of several fatalities owing to the panic it produces. The collapse of the bag may be caused by a leak in the apparatus at a place where the internal pressure is positive. The most frequent cause, however, has been the action of the automatic blow-off valve on an expiratory bag, as in the Draeger apparatus, or on an expiratory tube, as in the case of the liquid air apparatus. With the excessive breathing induced by considerable exertion or by an excess of inhaled CO2. the air has not been able to escape easily onwards from the expiratory bag or tube. The consequence has been that the escape valve has acted freely, and so much air has escaped that the inspiratory bag has been unable to fill fast enough, and has, therefore, collapsed rapidly. With an apparatus liable to this accident, any considerable exertion, or failure of the purifier, is evidently dangerous. Collapse of the bag may also be caused by accidental pressure on the bag. This is specially apt to happen when the wearer is bending or crawling. In certain apparatus, such as the Proto, the design is such that the risk of collapse of the inspiratory bag is avoided entirely. 6. Excessive Resistance to Breathing.—(a) Resistance may be due to choking of the purifier, to sticking of the valves, to insufficient area of the air passages, or to the accumulation of water or (in liquid air apparatus) of ice in those passages. Whatever may be the cause of the resis’ance, the effect is to create a considerable difference in pressure at the mouthpiece between expiration and inspiration. Apart from the discomfort in breathing, the risks of leakage, both inwards and outwards, are greatly increased by resistance in the circuit. Even the mouthpiece is liable to leak in such circumstances. (&) A highly distended apparatus, due perhaps to the relief valve failing to operate, is un- comfortable to use owing to the exertion needed on exhaling, and, unless the pressure can be relieved, may lead to serious difficulty. No apparatus can be considered satisfactory in which, while walking at four miles per hour, there is discomfort due to either of the above-mentioned causes of resist- ance. 7. Temperature of the Inspired Air becoming Exces- sive.—The capacity for work is greatly reduced and the discomfort of using the apparatus much increased by a high wet-bulb temperature. An apparatus should be regarded as unsatisfactory if the wet-bulb tempera- ture of the inspired air exceeds 105 degs. F. (40^ degs. C.) under the temperature conditions commonly met with in the mine. 8. Failure due to Rise in Body Temperature.—This is apt to occur when the wet-bulb temperature of the mine exceeds 80 degs. F. In some forms of apparatus the heat of the purifier may be a contributory cause. To minimise this danger unnecessary clothing should be discarded in hot mines, excessive exertion avoided, and protection afforded against conduction or radiation of heat from the purifier. It is important that, during training, men should experience the effects of high wet-bulb temperatures, and so learn how to escape risks from this cause. 9. Faulty Construction or Material.—Only the best and most suitable material should be employed in making rescue apparatus, and only the best workman- ship and finish should be permitted. Individual parts should be correctly designed for the duty they have to perform. All metal surfaces intended to encourage radiation should be finished in dull black. Screws should be standard Whitworth gas thread. Gauzes should be so held that no part of them can become detached. Supply pipes and other fittings should either be fixed so as to lie close to the body, or should be enclosed so as not to be liable to get damaged or detached by contact with projections in the passages of the mine. The apparatus ought to incommode the wearer as little as possible, particularly when he is in a stooping or crawling position. It should also permit free vision in that position. Helmet and Face-mask. The Committee are glad to find an almost complete unanimity among rescue station instructors in con- demning the so-called helmet as an attachment to self- contained breathing apparatus. It suffers from the objections that it cannot be made an air-tight fit in all cases, and that, as already explained, it entails grave risk of the wearer being disabled by CO2. These defects are so overwhelming that a discussion of the merits of the helmet would be a waste of time. The face-mask, which covers the nose and mouth, leaving the rest of the face exposed, is preferred by some instructors. Though certain of the better masks, such as that used with the Weg apparatus, afford some degree of security against leakage when the pneumatic j int is tight, the breathing easy, and the wearer’s face smooth and well filled-out, none of the face masks examined give proper security when worn by a person having hairy or sunken cheeks, or by one whose cheeks readily fall in when drawing breath against a slight resistance. The mouthpiece is the only attachment independent of such considerations, and the only one on which reliance can be placed. The Committee recom- mend that the existing types of helmet and face-mask be abolished in so far as self-contained apparatus are concerned. The Oxygen-feed. In a subsequent report it is intended to deal at length with the various matters bearing upon oxygen supply, but action without delay is recommended on the following points:— Preventing Main Valve being closed during Work.— The main oxygen valve should be so arranged that it is impossible for it to be turned off accidentally while the apparatus is in use. The necessity of this precaution was demonstrated by the case of Captain Ramsay, Superintendent of the Elswick (Newcastle) Station, on June 6, 1913, who died from oxygen starvation while wearing the Proto apparatus. The valve was found shut, and possibly may have been closed by contact with the floor or supports of the drift in which a practice was being undertaken. A similar occurrence, though less serious, took place during recent (1917) tests of apparatus at Mansfield, the Proto again being worn, but without the safety catch supplied by the makers. Several cases are on record of men, on starting a practice, turning off their oxygen under the impression that they were turning it on; and in America three instances have been noted of men forgetting to open the oxygen valve before closing the apparatus and applying the noseclip. When the bag is properly flushed out with oxygen at the start accidents from these causes cannot occur. Sunk-Spindle Oxygen Valve Recommended. — The handwheels of the main valves of the latest Proto and Draeger apparatus are fitted with locking contrivances to prevent accidental shutting of the valve and another locking contrivance designed by Mr. Macaskill is in use at the Doncaster rescue station; but the Committee think that the adoption of the sunk-spindle valve, one design of which is shown in fig. 1, would result in a more complete immunity from the occurrences referred to above. This fitting has given good results at the Edinburgh station. The key (fig. 2) is double ended. The box-spanner serves to turn the square-ended valve spindle S, whilst the jaw-spanner is required when tightening or slackening the screw-cap C. The latter prevents the escape of oxygen should there be leakage along the spindle—a common defect. Danger of Insufficiently Opening Valve.—The men should be warned against opening a main valve insuffi- ciently. A fraction of a turn may be enough to release enough oxygen under 120 atmospheres pressure; but when the pressure has sunk a good deal the flow may be checked if the valve is left in that state. The cock should always be opened wide. Unsuitable Design of Proto Valve.—The main valve of the older Proto apparatus compares unfavourably with that of the latest form or with the Meco or Draeger valves, it being possible, with the first, to continue unscrewing until the valve spindle is withdrawn, when all the oxygen is at once lost. The locking chain and spring hook fitted to the Proto was originally applied by Mr. W. Clifford, of Stoke-on-Trent station, as a means of preventing the valve being rotated more than a safe number of turns when it is being opened. It would be preferable, however, to refit all these apparatus with valves of better design. A further drawback of the older type of Proto valve lies in the use of a stuffing-box round the spindle. This form of gland is difficult to keep tight. These remarks also apply to the by-pass and pressure gauge valves of the Proto apparatus. The new Proto and the Meco and Draeger valves are almost identical. That shown in fig. 1 is a Meco valve. The valve proper V and the short square rod R are the only portions with up-and-down-movement. The spindle merely rotates. The flat fibre washer W takes the place SQUARE ROD CYLINDER CONNECTION^ c _^5WIVEL RING Figs. 1 and 2.—Sunk Spindle Valve and Key. of the stuffing-box of the original Proto form ; more- over, it is only possible to unscrew a few turns, i.e., until the valve moves up against the bottom of the spindle. Insufficient Oxygen Supply at certain Proto Stations.— The majority of self-contained apparatus depend upon a uniform oxygen feed which is not under the control of the wearer. In all the cases which have come under observation this feed has been adjusted to be about two litres per minute, with the {exception of certain Proto stations where a lower rate of feed has been adopted, the by-pass being used to reinflate the bag should it become exhausted. Evidence, however, goes to show that at these stations, during gallery practices at any rate, the additional quantity supplied by the by-pass is relatively small, it being usual to find the cylinders half full after two hours service. Oxygen Consumed in Climbing Underground Inclines. Drs. Haldane and Briggs have made measurements in the mine of the amount of oxygen consumed by men carrying rescue apparatus while climbing inclines, but breathing ordinary air. The results will be given in full in the second report; but a few averages are cited, in order to show how markedly the consumption may differ in actual operations from that in a training gallery, as exemplified by the case under notice, and how risky unduly low feeds must be. The oxygen volume used is expressed in litres per minute at 32 degs. Fahr, and 30 in. barometer :— Gradient of roadway. 1 in 6| 1 in 5 1 in 3| 1 in 2 Average speed. Miles per hour. Average oxygen consumed. Litres per minute. 2*15 1’49 2’05 2’12 162 2’32 1’06 2’60 It is important to realise the nature of the experience which has resulted in dangerously low feeds being adopted at some Proto stations. They were not intro- duced merely to save oxygen, but because the men find