Codes & Safety第 118 / 120 题
Before anyone enters a 12 ft deep sewer manhole classified as a permit-required confined space, the atmosphere is tested and the meter reads 19.2 percent oxygen. What is the correct interpretation, and in what order must the atmosphere be tested?
a.The reading is acceptable, and the correct order is toxics first, then oxygen, then flammables
b.The reading indicates an oxygen-enriched atmosphere, and the correct order is flammables first, then oxygen, then toxics
c.The reading is oxygen deficient, and the space must be tested for oxygen first, then flammable gases and vapors, then toxic contaminants
d.The reading is acceptable as long as the entrant wears a filtering facepiece respirator and an attendant is posted
解析
An acceptable atmosphere holds oxygen between 19.5 and 23.5 percent, so 19.2 percent is oxygen deficient and entry is prohibited until the space is ventilated and retested. Testing follows a fixed order of oxygen, then flammables, then toxics, because combustible gas sensors need oxygen to give a valid reading and a low oxygen result makes the flammability reading unreliable. An enriched atmosphere is above 23.5 percent, not below 19.5. A filtering facepiece only removes contaminants from the air; it cannot add oxygen, so it is never permitted in an oxygen-deficient space, which requires supplied air along with an attendant, a signed entry permit and a retrieval system.
法律依据: 29 CFR 1910.146免费刷完整 120 道题库 — 无需注册。
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