Compressed Air Work And Diving 1909

12 COAfPRESSED AIR HERR. The custom has usually been to work one and a half hours twice a day at a pressure of 45 Ibs., and it will perhaps be well, until further practical experience is avail- able, that exposures at 45 Ibs. should not exceecl two hours, at 40 Ibs. should not exceecl three hours, and at 35 Ibs. should not exceecl four hours. Saturation is practically complete in six hours, so that the lengtlis of time to be spent in the lock after six hours’ exposure will also serve for longer exposures. Tables VI. and VII.—These two tables are for use after curative recompression in the medical lock, or after preventive recompression made necessary by some acci- dent, such for instance as a burst dress in the case of a diver, or a cracked cast-iron cylinder in caisson work. When a worker is suddenly decompressed by some such accident as one of these, he should immediately be placed in the air-lock, and the pressure raised as quickly as possible up to, or very nearly up to, the pressure he has just been working at. If no symptoms appear, or when those which have appearecl have disappeared, the pressure should be slowly and cautiously lowerecl to about half the absolute working pressure. It should then be lowerecl in stages, with stoppages every 5 Ibs. as given in the tables. After recompression in the air-lock, decompres- sion should be very slow and cautious, as the bubbles may not have become completely clissolvecl during the recompression. It is inadvisable to keep a patient long at pressures above 45 Ibs., so that if at any time it is necessary to recompress at pressures higher than this a start should be made in lowering the pressure very soon after the patient has entereel the air-lock. The two tables have been calculated for three hours’ and six hours’ adclcd exposure respectively. To find