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
QRT
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
1000
0.5
0.1
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:
dB 10 log I
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
3
6
1000
b) Ventillation rate in m3/s
1
3
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