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Apr 26, 2023

QUESTION 1: A process involves the removal of oil and other liquid contaminants from metal parts using a heat-treat oven, which has a volume of 15,000 ft3. The oven is free of solvent vapors. The ventilation rate of the oven is 2,100 cfm, and the safety factor (K) is 3. The solvent used in the process evaporates at a rate of 0.6 cfm (cubic feet per minute). The operator would like to know how long it would take the concentration to reach 425 ppm.


Your response must be at least 200 words in length.

QUESTION 2: Your quality control/quality assurance manager has requested your assistance in the testing and repair facility. One of the test procedures utilizes a radiation source that is emitting gamma radiation at a rate of 50 mrem/hour at a distance of 1 foot. This testing is done for approximately 2 hours per day, 2 days per week. The Occupational Safety and Health Administration (OSHA) has a PEL of 1.25 rem per quarter and 5 rem per year.

a. Determine the employee’s exposure for 1 year.
b. Calculate the exposure rate if the employee was moved to a distance of 3 feet from the radiation source.
c. Calculate the exposure rate of the employee if a 5 cm lead shield was installed between the source and the detector. The employee is working at a distance of 1 foot from the source. [µ for lead, (662 keV gamma ray) = 1.23cm-1]

Your response must be at least 200 words in length.

QUESTION 3: The maintenance manager of your facility has asked you to evaluate a particular welding booth that utilizes a local exhaust ventilation (LEV) system to remove the contaminant at the source. The exhaust system does not appear to be drawing enough of the welding fumes away from the employees to reduce the iron oxide below the permissible exposure limit (PEL) of 10 mg/m3. During your investigation, you determine that the diameter of the duct system is 8 inches and has an air velocity of 350 fpm (feet per minute). The welding operation is performed at a distance of 1.5 feet from the exhaust opening. Determine the flow rate, and provide your recommendations on the control measures that could improve the capture of the iron oxide contaminant.

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