Threshold Limit Value (TLV) denotes the maximum acceptable concentration for workplace exposure; the TLV (ceiling) for phosgene in air is about 0.1 ppm (parts per million).
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A0.002 ppm
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B0.05 ppm
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C0.1 ppm
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D0.2 ppm
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E1.2 ppm
Answer
Correct Answer: 0.1 ppm
Explanation
Introduction / Context:Phosgene (COCl2) is a highly toxic industrial gas. Occupational exposure guidelines define maximum allowable concentrations to protect worker health. TLV values are typically expressed as TWA (time-weighted average), STEL (short-term exposure limit), or ceiling limits that should never be exceeded.
Given Data / Assumptions:
- We are interested in an accepted, practical TLV for phosgene.
- Many standards cite a very low ceiling value around 0.1 ppm due to high toxicity.
Concept / Approach:Relate health risk to dose: even brief exposures to phosgene can cause severe respiratory injury. Therefore, limits are set extremely low, and a ceiling (instantaneous) cap is appropriate for control.
Step-by-Step Solution:
1) Identify phosgene as a pulmonary irritant causing delayed-onset edema.2) Recall standard occupational guidance: limit near 0.1 ppm as a ceiling.3) Choose the option that matches 0.1 ppm.Verification / Alternative check:Cross-reference safety datasheets and occupational hygiene references that list a 0.1 ppm ceiling; different jurisdictions may use closely related values, but 0.1 ppm is widely recognized.
Why Other Options Are Wrong:
0.002 ppm and 0.05 ppm: more conservative than typical regulatory or consensus TLVs.0.2 ppm: double the recognized ceiling; risk of underprotection.1.2 ppm: orders of magnitude too high.Common Pitfalls:Confusing TWA with ceiling limits; ignoring the need for immediate alarms and leak detection for phosgene.
Final Answer:0.1 ppm