Module 4 – Exercises 4-1 and 4-2
Exercise 4-1
While inspecting a manufacturing plant you enter the break room where they permit
smoking. The break room is 10 feet (3.05 m) by 10 feet (3.05 m) with an 8 -foot (2.44 m)
ceiling. Opposite the door is an old sofa with cotton padding and cotton fabric. It is
evident that smokers use the sofa since there is an ashtray next to it. There is a lighted
exit sign over the doorway.
You point out to the manager the dangers of a flammable sofa in the break room. (He is
adamant that he won’t restrict smoking.) You also mention the need to make sure the
exit sign light is on.
To illustrate your points you calculate the sign’s visibility to someone sitting in the sofa
for various stages of a fire. You do this for several stages of the fire with the exit sign
light on and off. You use the following fire stages, assuming that the cotton produces
smoke similar to Douglas fir wood:
Exercise 4-2
Firefighters respond to a hotel fire. An occupant is sleeping in a room where the carbon
monoxide concentration is 10,000 ppm. Firefighters have about 5 minutes to affect
rescue before victim becomes incapacitated. Can they make it?
There is a fire at the atrium floor of an apartment building. The fire’s heat release rate is
4,500 kW. The building is 76 ft (25.2 m) high. The inside temperature is 70°F and the
outside temperature is 28°F.
1. Find the neutral plane.
2. Calculate the fire plume’s mass flow rate at the neutral plane height.
3. The desired smoke depth at the ceiling is about 10 ft (3.05 m). Find the mass
flow rate at the base of the smoke layer.
4. Determine the size vent needed to maintain the smoke at the desired depth.
5. Explain why the mass flow rate at the neutral plane is less than that at the bottom
of the smoke layer.
General Instructions for Exercises
Questions involving calculations are best submitted using Equation Editor in Microsoft
Word. This is an easy way to clearly show equations. Even if you don’t have the correct
answer, you may receive partial credit on computation problems if you show all your
calculations.
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