(i) A chemical laboratory has violated the threshold limit values-time weighted

Question

(i) A chemical laboratory has violated the threshold limit values-time weighted average (TLV-TWA) of toluene (100 ppm) exposure for the 8-hour workers in the laboratory.
a. If the workers were exposed to 300 ppm for the first two hours and the measured TWA is 125 ppm, calculate the average measured toluene concentration in ppm for the remaining 6 hrs.
b. What will be the best solution as temporary measures for all employees working in the laboratory?
(ii) The chemical laboratory tried to decrease the exposure of toluene and design an enclosed system for the handling of the toluene.
a. Describe the equation to estimate the average concentration of toluene in an enclosed system and explain the assumptions considered in the calculation.
b. Estimate the average evaporization rate of volatile matter (unit: ft3/min) if the toluene container is in an enclosure with ventilation rate is 98 ft3/min. The toluene is at 80F and 1 atm pressure with calculated kCppm = 10 ppm.
(iii) The need to have a control during microbiological work in a biotechnological plant is very important. This is to prevent contamination of the open area or room. Describe an ideal ventilation technique that can be used and give the advantages and disadvantages.

Explanation / Answer

i) b) The best solution as temporary measures for all employees working in the laboratory should be that the workers should be allowed to work for certain interval of time and then given breaks of sufficient intervals so as they are exposed to only the threshold levels.

ii) b) Average rate of evaporization : (ventilation rate * P) / (R* T* C)

Where P = Pressure

V = Volume

T = Temperature(in kelvin) [ 32degree F = 273.15 K]

C = Concentration

R = Gas Constant (0.0821  L atm mol-1 K-1)

(98 * 1) / (0.0821 * 299.81 * 10 * 10-3)

Average evaporization rate = 398.1 ft3/min

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