Document mLGxR83oeX2zzYMQe5yjXY7O

Fic 19-33 --Solder grinders wear hoods to prevent foreign matter from entering their eyes, ears, noses, or mouths Filtered air is supplied to the hoods at 12 to 15 psig and is exhausted around the bottoms bons of rapidly moving abrasive pai tides The requirements for abrasive blashng respirators are the same as those for an air line respirator of the continuous flow type, with the addition that mechanical protection from the abrasive particles is needed for the head and neck (Fig 19-32) NIOSH-MESA tests and ceitifies such equipment There are two foims of abiasive blasting respirators that cover the head and neck, and even the shoulder and chest One form has a full facepiece (made of rubber), and an eyepiece made of impactresistant safety glass (or plastic covered by a metal screen) This unit is attached securely to a hood and cape made of tough, flexible rubber or rubber-covered fabnc Air is supplied to the full facepiece and is exhausted through an exhalation valve located under the hood in order to expel the air at the edges of the hood The other form uses a rigid helmet (gen erally made of metal) to encase the user's head The eyepiece is of impact-resistant safety glass or of plastic covered by a metal screen An adjustable knitted fabric collar, covered with rubber- or plastic-coated fabnc, fits over the metal helmet and down over the user's neck, shoulders, and chest in order to give addibonal protecbon A flexible tube brings air to the helmet Air, exhausted from the helmet, flows between the collar and the user's neck In both units, the eyepiece (window) and the protechve screen should be easily re placeable, preferably without the use of tools Air supplied hoods For some long-term operabons where a completely enclosed suit is not necessary, an air supplied hood may be used These are particularly useful in hot, dusty situabons. Fig 19-33 Respirable air under suitable pressure should be delivered to a hood at a volume of at least 6 cfm Air supplied suits The most extreme condibon requiring re spiratory equipment is that m which rescue or emergency repair work must be done m atmospheres extremely corrosive to the skin and mucous membranes, m addition to being acutely poisonous and immediately hazaidous to life, such as atmospheres containing am monia, or hydrofluoric or hydrochloric acid vapois For these conditions a complete suit of impervious clothing, with a respirable air sup ply, is available (Fig 19-34) Complete units with self-contained breathing apparatus are discussed under "Self-contained breath ing devices,'' which follows this secbon There are no generally accepted specifica tions for such suits, therefore considerable dependence must be placed upon the manu facturer The material should have sufficient mechanical strength to resist rough handling and considerable abuse without tearing The hose line supplying the air should be connected to the suit itself, as well as to the helmet (Fig 19-35), since it is not only ex tremely fatiguing but also dangerous to wear such a suit for a long penod unless it is well venblated Personal air conditioning devices utilizing a vortex tube are available for air supplied suits or hoods These cooling devices are desirable to reduce fabgue where high am- 501