LPG odorization: Ethyl mercaptan is added to Doctor-negative LPG to aid leak detection by odor. What is the typical target treat rate (ppm by volume) used in practice?
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A1
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B50
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C5000
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D10000
Answer
Correct Answer: 50
Explanation
Introduction / Context:LPG is naturally odorless. For safety, an odorant such as ethyl mercaptan is added so even small leaks are detectable by smell in domestic and industrial use.
Given Data / Assumptions:
- Product: Doctor-negative LPG (sweet, low sulphur).
- Odorant: ethyl mercaptan added at a controlled trace level.
- Units: parts per million (ppm) by volume equivalent.
Concept / Approach:Odorization balances detectability with handling safety and product quality. Regulatory and industry guidance typically specify a low two-digit ppm range to ensure recognizability without excessive sulphur addition.
Step-by-Step Solution:
Step 1: Recall common practice values in the ~10–50 ppm band.Step 2: Among the options, 50 ppm is the only realistic figure consistent with standard odorization targets.Step 3: Select 50 ppm.Verification / Alternative check:Operational guidelines and national safety codes often cite approximately 20–50 ppm as typical treat rates, confirming the order of magnitude.
Why Other Options Are Wrong:
- 1 ppm: Too low for reliable human detection in varied conditions.
- 5000 / 10000 ppm: Excessive and impractical; would severely affect sulphur specification and odor intensity.
Common Pitfalls:Confusing mg/m^3 and ppm or assuming higher is always better; overdosing has drawbacks.
Final Answer:50