Safety第 96 / 110 题
Before entry, a manhole 4 ft in diameter and 12 ft deep must be purged with 5 air changes. Using volume = 0.785 x diameter^2 x depth (about 151 ft^3), what total air volume must be moved to complete the purge?
a.151 ft^3
b.302 ft^3
c.1,510 ft^3
d.755 ft^3
解析
Space volume = 0.785 x 4^2 x 12 = 0.785 x 16 x 12 = 151 ft^3, and 5 air changes require 5 x 151 = 755 ft^3 of air moved. Purging several air changes before entry clears hydrogen sulfide and methane and restores oxygen. The atmosphere is then re-tested in the order oxygen, flammable, toxic before anyone enters.
法律依据: 29 CFR 1910.146免费刷完整 110 道题库 — 无需注册。
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