Problem:
Ventilation is the extremely significant technique of diminishing the level of toxic airborne contaminants in workplace. Since it is impossible to get rid of absolutely all leakages from a process in the workplace, some technique is always required to remove toxic materials from the air in closed rooms when such materials are present in process streams. The occupational safety and health administration (OSHA) has set the permissible exposure limit (PEL) of vinyl chloride at 1.0 ppm as a maximum time-weighted average (TWA) for an eight hour workday, since vinyl chloride is believed to be a carcinogen. If VC escaped in the air, its concentration should be maintained at or below the PEL.
Required:
Question 1: If a process loses 0.001m3/hr of Vinyl chloride in the room air, what volumetric flow rate of air will be essential to maintain the PEL of 1.0 ppm by dilution ventilation? (In practice we should also correct for the fact that complete mixing will not be realized in room and in this case the mixing factor is supposed to be 10).
Question 2: If the safety analysis of ventilation doesn’t demonstrate a safe concentration of Vinyl chloride exists, the process may have to be moved in a hood so that no Vinyl Chloride enters the room. If the process is performed in a hood with an opening of 30 cm wide by 25 cm high and the “face velocity” (average air velocity through the hood opening) is 10 m/s, what is the volumetric ai flow rate?
Question 3: Which techniques of treating the pollution problem seems to be the best to you? Illustrate out your answer.
Question 4: Illustrate out why dilution ventilation is not suggested for maintaining air quality?
Question 5: What might be a problem with the employ of a hood?