Perchloroethylene (PERC) is the most commonly used dry cleaning solvent in the U

Question

Perchloroethylene (PERC) is the most commonly used dry cleaning solvent in the U.S. PERC is considered a potential human carcinogen and can cause severe impacts if absorbed into the body through respiratory and dermal exposure. The U.S. Department of Health and Human Services and the Center for Disease Control have guidelines on ventilation for commercial dry cleaning facilities. You are hired to evaluate the air quality in an apartment above a dry cleaning facility. The apartment, which has a floor area of 40 m^2 and a ceiling at a height of 15 m, has an indoor PERC emission flux of 0.06 mg*m^-2 * hr^-1 due to air flow through the walls of the building. The apartment has a ventilation rate of 0.3 hr^-1 and is exposed to an additional PERC average inflow concentration of 0.03 mg/m^3 through the windows. The new guideline for PERC from the New York State Department of Health is 0.03 mg/m^3 for chronic air exposure. Estimate the steady-state concentration of PERC in the apartment above the dry cleaning facility. Is this level below the recommended SCOEL levels? The residents of the upstairs apartment install a new filter to get the PERC concentration in the apartment below the standard 0.03 mg/m^3. At what reaction rate (kr) does the filter needs to operate in order for the apartment to meet the air quality standards for PERC with continued emissions?

Explanation / Answer

inflow through celling and walls = 0.06*40 + 0.06*(8*15*2 + 5*15*2) = 25.8 [ where it is assumed length of walls are 8 and 5 m respectevlt)

ventilation rate = 0.3

overall steady state concentration is = 25.8 - 0.3 = 25.3 mg in 600 m3

hence, steady state concentration = (25.3 /600) = 0.043 mg/m3

as per Scientific Committee on Occupational Exposure Limits (SCOEL), the recommended levels is 20 ppm or 20 mg/L

Here steady state concentration is  0.043 mg/m3 = 0.000043 mg /L

yes this is below the SCOEL levels.

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