Chapter 7 - Ventilation Systems Flashcards
What is a fire department’s first concern at a high-rise fire?
Getting people out of the path of danger.
What kills most people in high rise fires?
Smoke.
What is one of the most crucial elements of managing high-rise fires?
Understanding smoke movement. p117
What are the three big shafts that were most concerned with?
Stairwells.
Elevator hoistways.
Ventilation shafts.
What is the most obvious natural force that moves smoke into shafts and other floors?
The pressure generated by the fire.
What is the force that causes air to move up in buildings on cold days or down on hot days?
Stack effect.
On cold days the air moves which direction?
From the bottom of the building to the top.
Stack effect has greater velocity on what type of day?
Colder days.
Temperature difference is much greater.
What is the point halfway up the building where air neither enters nor exits the building?
The neutral pressure plane.
If the openings in the bottom half of the building are increased, the neutral pressure plane will what?
Drop to a lower level.
Where is the personnel staging floor usually located?
Usually two floors below the fire.
What is something that is highly instrumental in increasing stack effect?
Open stairwell doors.
What is important to monitor in reverse stack effect situations?
Carbon monoxide.
What is a particular problem when a fire is above the neutral pressure plane?
Reverse stack effect.
Stairwell doors have what dimensions for smoke to get through?
18 square inches.
Through the evacuation process what is very important?
For all doors to be kept closed as much as possible.
Chances for a safe evacuation by stairwells are greatly diminished if what happens?
If the stairs are not pressurized.
A closed elevator hoistaway door has a leakage area of approximately what?
0.6 square feet.
What is the most common method to keep smoke out of elevator shafts?
Enclose elevator lobbies on each floor with normally open doors that close automatically upon alarm.
What is one of an incident commander’s best tools in regards to ventilation systems?
An elevator riser diagram showing each hoist way and the floors each elevator opens on.
Smoke spread through ventilation shafts is largely limited to where?
The involved zone.
The shutting down a ventilation systems is usually what?
Best avoided.
Most fire alarm systems are carefully designed to prevent fans from doing what?
Spreading smoke to other floors.
In most AHU systems the coils are cooled by what?
Passing cold water through them.
