December 2, 2020

End of Problem 3-7

Problem 3-8

Xylene is used in a hood that has a face area of 4.65 sq m, with a

temperature of 25 deg. C and at 1 atm. a) Determine the dilution ventilation

required to keep the area concentration below the TLV-TWA. and b) Compare

this rate to the recommended face velocity for hoods. The determined

evaporation rate is 11.6 liters in 8 hours.

Solution 3-8

End of Problem 3-8

Problem 3-9

Determine the recommended air rate that is required for a hood

having face dimensions of 1.22 m high and 0.91 m in width.

Solution 3-9

The recommended face velocity is between 80 and 120 ft/min. Assume a

End of Problem 3-9

Problem 3-10

If the hood in Problem 3-10 is used for handling trichloroethylene, determine

the rate of air passing into the hood face to keep the concentration a) below

the TLV-TWA and b) below the lower explosive limit. And c) compare these

rates with the recommended rate shown in Problem 3-10. The temperature is

25 deg C and the pressure is 1 atm. In all cases the evaporation rate is 0.04

kg/min.

Solution 3-10

The Using the GHS SDS the TLV-TWA is 100 ,ppm and the lower explosive

a) These are the volume rates to keep below the TLV-TWA.

End of Problem 3-10

Problem 3-11. Use Safety Data Sheets to determine the TLV,

and NFPA ratings for ethanol, chlorine, and phosgene.

Solution 3-11 Ratings

End of Problem 3-11

Problem 3-12. a. A worker is exposed to multiple sound

sources; i.e. I=I1+I2+ . . . Ii = ΣIi

Derive the following equation for the net sound exposure from these

multiple sources or

/10

10

1

10 log 10 i

n

dB

i

dB

b. Two sound sources are at 90 dBA. What is the net exposure from

these two sound souuces?

Solution

a. The derivation follows:

b. The net exposure for the two sound sources:

End of Problem 3-12

Problem 3-13. Two liters of a liquid chemical is spilled on the laboratory floor. Assume 1 atm, 25

o

C.

a. If the liquid pool is 2 mm deep, calculate the area of the pool.

b. What ventilation rate, in m3/s, is required to prevent the air concentration from exceeding the TL

V

for the chemical of 100 ppm?

c. Ventilation air is provided for the lab via a 0.5 m square duct. The air velocity exiting the duct is

measured with a velometer at 30 m/s. Calculate the volumetric flow of air from this duct in m3/s.

Is this adequate ventilation for this spill?

Data for the liquid chemical:

Molecular weight: 100

Saturation vapor pressure of chemical at 25

o

C: 100 mm Hg

Solution to Problem 3-13

a) Area if pool with depth of 2 mm

b) Ventillation rate in m3/s

c) determine if the actual ventilation rate is adequate

End of Problem 3-13

Problem 3-14. A large workshop uses a 2:1 mixture by volume of liquid xylene and hexane to strip var

n

from antique furniture. A total of 15 liters are used per 8 hour shift. The workshop is maintained a

t

25

o

C and 1 atm and has a ventilation system that provides 1 m3/s of fresh air. Is the ventilation sys

adequate to maintain the concentrations below the TLV-TWAs?

Xylene: molecular weight: 106.16, specific gravity: 0.870. TLV-TWA: 100 ppm

Hexane: molecular weight: 86.18, specific gravity: 0.657, TLV-TWA: 50 ppm

Solution to Problem 3-14

End of Problem 3-14