Document X6xED8E3oVQv8q2oMLjY7JqR

breathing apparatus This can be either a compressed-air type of self-contained breath ing apparatus, or self-generating or air sup plied type The fit of the facepiece should be carefully checked before the workman enters the tank If the environment contains a sub stance that is dangerously irritant or corrosive to the skin (lead tetraethyl, for example), the breathing apparatus may be supplemented by complete attire of impervious clothing Some medical authorities advise that in dividuals with broken eardrums not work m vapor-laden atmospheres, because no mask will protect these abnormal openings The supplied fresh-air hose mask with blower is generally the best type of respira tory equipment for continuous use inside a tank Proper procedures A tank should be gas freed before any work is performed inside it A worker should not be allowed to enter a gassy or oxygen-deficient tank unless abso lutely necessary, such as m an emergency When this is necessary, the man should be attended on the outside by another worker who is similarly outfitted with appropriate respiratory protection and protective attire as needed so that the latter can rescue the man in the tank if necessary In some states this is a legal requirement Men engaged in tank cleaning should be instructed in the method of giving artificial respiration, and should be retrained peri odically If a tank cleaner is overcome by vapor or gas, he should be removed to fresh air immediately and given artificial respira tion until he resumes breathing A physician should be summoned, and the resuscitated man kept quiet and warm until breathing and circulation are normal The sense of smell cannot be relied upon for an accurate estimate of the amount of flammable vapor present in a tank It does, however, give warning that vapors of some kind are present Symptoms of dizziness, nausea, and headache indicate that a danger ous concentration of flammable and toxic vapors is present Exposed workers should leave the contaminated area immediately and not return until vapors have been cleared Workers should always have a clear path of escape from a tank and should bear m mind that they may have to use it in a hurry A ladder should always be used when a tank must be entered from above, and it should be left secured in place until the last man is out of the tank Under severe conditions, a life line is recommended to assist with rescue work Burning, welding, cutting, and spark-producing operations should not be permitted in a tank until the area to be heated has been thoroughly cleaned and tests have determined that the tank atmosphere is vapor free Where any vapor is present, further ventilation will be required to remove the vapor from the tank Hot work repairs (welding and cutting) should not be made whenever other means can be used more safely Even after a tank has been freed of vapor, combustible mixtures again may be formed through admission of flammable vapors or liquids from other sources, such as an unblanked line or connec tion, a break m the bottom of the tank, sludge, sediment, or sidewall scale, or wood struc tures soaked with the liquid The interior framing of floating tank roofs can trap quan tities of liquids that will release vapors Therefore, periodic tests with a combustible gas indicator should be made during the hot work Burning or cutting may release lead fumes from paint on either the inner or outer sur face of the tank or from some other source An approved mask for protection against lead may be necessary, or it may be advisable to exhaust the fumes Wood supports inside the tank should be protected or removed before hot work is begun Some companies use low-voltage trans formers to eliminate the danger of electric shock, especially when men are required to work in wet areas All portable electrical equipment should be grounded Cold work in a tank may present a dust problem, and approved dust respirators and goggles should be worn if tests definitely show that wearing of a hose mask is not necessary Gas tests should be made frequently if the presence of gas is suspected The concen tration of gas or vapor m a tank or vessel may increase as work progresses, especially if the inside of the tank is scraped or heated dunng the operation 1037