How to Answer Time Weighted Average Questions (Complete Guide)

Students often encounter this when studying fundamental concepts.

What This Question Is About

This question relates to time weighted average and requires a structured academic response.

How to Approach This Question

Structure your response with introduction, analysis, and conclusion.

Key Explanation

This topic involves time weighted average. A strong answer should include explanation, application, and examples.

Original Question

Time-Weighted Average Exposure calculations: Sample No. Concentration Sampling Time 1 550ppm 1.5 hours 2 400ppm 5.8 hours 3 375ppm 1.7 hours C = Concentration of the contaminant T = Time period during which this concentration was measured TWA = Time-Weighted Average TWA=C1 T1 +C2 T2 +C3 T3 9hrs This study source was downloaded by 100000787154157 from CourseHero.com on 06-12-2025 21:20:41 GMT -05:00 https://www.coursehero.com/file/237314993/Advanced-Occupational-Safety-and-Healthdocx/ =3,782.5 ppm ( 1.5h)(550 ppm)+(5.8h)(400 ppm)+(1.7h)(375 ppm) 9h ¿472.8125 ppm Modified Permissible Exposure Limit (PEL) calculations: Hexane has an OSHA PEL of 500ppm PELnhours = PEL(orTLV )x8h (actual shifthoursworked) PEL12hours =500 ppm x8h 12h PEL12hours =4000 ppmâ‹°h 12h PEL12hours =333.33 ppm 9h Contaminant Concentration (Time-Weighted Average) PEL Hexane 472.8125ppm Results of Option #1 Ventilation System General Dilution Ventilation Room Air Change Calculations: Q = Actual Ventilation Rate V = Volume of Room Nchanges = Number of room air changes Nchanges =60Q Vr Nchanges =60(1500cfm) 4500 333.33ppm Nchanges =20 / Hour

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