Special precautions are necessary in connection with cylinders or tanks containing compressed oxygen and acetylene gas, if accidents are to be avoided; and all other equipment used for welding and cutting must be kept in good repair and handled carefully and intelligently. The tanks should never be dropped or subjected to heavy blows or jarring; and they should not be left where they might be knocked over, or where heavy objects might fall on them. Electromagnets should not be used for hoisting compressed-gas tanks, and when lifting or lowering them by means of derricks or other hoisting devices, suitable cradles should be used in place of slings, in order to reduce to a minimum the possibility of dropping the tanks.

When compressed-gas tanks are in use they should be located as near as possible to the point where the work is being done, so that long lengths of hose will not be required to connect the tanks with the welding or cutting torches. Tanks should be lashed or otherwise securely fastened in place when the conditions at the point where they are being used are such that they may fall to a lower floor or to the ground, if not so secured.

Full tanks should be protected from the weather while in storage; they should not be stored near boilers, furnaces, or other heat-sources, nor should they be exposed for any considerable time to the direct rays of the sun, because heat will increase the pressure and may cause the tanks to rupture. Never use open lights or flames of any kind in places where compressed-gas cylinders are stored. Keep all oily and greasy sub-stances away from oxygen cylinders and apparatus. Acetylene tanks should be stored in an upright position, and they should also stand on end when in use. Always close the valves on cylinders that are supposed to be empty, before placing them in storage or shipping them.

If a cylinder is received in a leaky condition, leave it out in the open air, but protect it in such a way that inquisitive persons cannot be harmed by the escaping gas. Never test for leaks with an open flame, but use soapsuds for this purpose, - the leaks will be indicated by bubbles.

The hose should not be connected directly to the gas cylinder, but to an automatic regulator or reducing valve screwed on to the outlet of the cylinder valve on the tank. When connecting the regulator to the cylinder valve make sure that there is no leakage at the joint or connection. To test this joint, first release the pressure-adjusting screw on the regulator and close the needle valve on the outlet of the regulator or on the inlet of the blowpipe. Then open the cylinder valve slowly and test the connection with soapsuds. If there is any leakage, be sure to close the cylinder valve before tightening the connection.

After connecting a new cylinder of compressed gas, and before lighting the gas at the torch, open the valve on the blowpipe or torch and let it remain open long enough to permit the escape of any gas mixture that may have remained in the hose from a previous operation.

If the use of the torch or blowpipe is discontinued but the hose remains connected to the automatic regulator or reducing valve, be sure to close the valve on the tank, to relieve the pressure on the hose.

Keep the hose and all other welding and cutting equipment in the best possible condition. Make all connections tight, using suitable clamps or binding wire for the purpose. Hose should be protected when in use so that it will not be trampled on nor heavy objects placed on it. Do not permit it to become tangled or kinked or subjected to severe twists or strains. All equipment that is not in use should be stored in a safe place.

13. Miscellaneous

One of the principal dangers in demolition work is that due to falling objects, and various phases of this hazard have been considered in some of the preceding paragraphs. In addition to the precautions already mentioned we may call attention to the necessity for protecting men who may be working on floors below the level at which the actual demolition operations are proceeding. To prevent injury to these men all floor openings should be kept covered, except when in actual use for lowering material; or if this is not feasible, toe-boards and hand-rails should be installed about them.

Care should be exercised in handling sheet metal roofing and cornices, because the edges of objects composed of this material may cause severe wounds. For the same reason no broken glass should be left lying about in the building.

The nail hazard is also an exceedingly important one in demolition work, and should receive much more attention than is usually given to it. As a rule, no attempt is made to remove or bend over the nails in boards, planks, and timbers that are stripped from the building, and doubtless the contractor feels that time cannot be spared to do it. We do not approve of laxity in this direction, and certainly there is no good reason for leaving boards with upturned nails lying about, as is the almost universal custom; because the boards can just as easily be piled with the nails pointing down, and it should be somebody's business to see that this is done. The nail hazard is considered in further detail in paragraph 64.

In demolishing buildings, stairs and stair railings should be left in place as long as possible, and be used for going up and down. Stairways are much safer and more convenient than ordinary ladders.

Dust resulting from demolition operations causes much annoyance and discomfort, and it is likely to get into the workmen's eyes and create more serious trouble. Floors, chutes, stairways, and various other places should therefore be sprinkled with water as often as may be necessary to keep down this dust.