If the flame of a miner’s safety lamp placed inside a manhole extinguishes within 5 minutes, the sewer atmosphere certainly contains_______________?
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Answer: B. Carbon dioxide
Explanation
The extinction of a miner's safety lamp flame within five minutes indicates severe oxygen depletion or the presence of asphyxiating gases like carbon dioxide. Carbon dioxide is heavier than air and frequently accumulates in stagnant subterranean manholes, displacing vital oxygen necessary for combustion. Flame extinction serves as a classic visual indicator that the manhole atmosphere is lethal and unsafe for unprotected human entry. Miner's safety lamps rely on ambient oxygen to maintain combustion; flames extinguish when oxygen levels drop below approximately sixteen percent. Carbon dioxide in sewers originates from aerobic respiration of microorganisms and carbonate dissolution in wastewater streams. Confined space entry safety regulations strictly prohibit relying solely on flame tests, mandating calibrated electronic multi-gas detectors.
Option A hydrogen sulphide is toxic and flammable, but low concentrations trigger severe irritation rather than immediate flame extinction. Option C methane is flammable and would typically cause the lamp flame to elongate or flare before any oxygen deficiency extinction occurs. Option D oxygen supports combustion, meaning adequate oxygen levels would keep the miner's safety lamp burning brightly instead of extinguishing.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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