Air Flow & Duct Work Flashcards
The conditions in the atmosphere refer to ______?
Weather
The density of air is:
How much air weighs per cubic foot
The specific volume of air is:
How much volume 1 pound of air occupies
The relative humidity of air is:
The percentage of moisture air is holding as opposed to the amount it could hold if it were saturated
As air is heated it:
Expands
The air pressure in a sealed balloon is:
Static pressure
A blower connected to a length of duct creates:
static pressure, which is then converted to velocity pressure
Velocity pressure is determined by:
Subtracting static pressure from total pressure
An inclined manometer is basically a:
U-tube manometer tilted at a steep angle
An inclined manometer is basically a:
U-tube manometer tilted at a steep angle
The static pressure of a duct is 1.76”, and the total pressure is 2”. What is the velocity pressure?
(Velocity Pressure = Total pressure - Static Pressure)
.24”
The static pressure of a duct is 1.76”, and the total pressure is 2”. What is the velocity pressure?
(Velocity Pressure = Total pressure - Static Pressure)
.24”
A pitot tube can directly measure:
Total and static pressures
How many holes must be made in a round duct in order to take a series of traverse readings?
Two
How many holes must be made in a round duct in order to take a series of traverse readings?
Two
A thermo-anemometer measures:
fpm directly
Dehumidification occurs when an air conditioning coil:
operates at or below the dew point of the air moving across it
Dehumidification occurs when an air conditioning coil:
operates at or below the dew point of the air moving across it
When testing a duct system to determine its leakage rate, why is a special test stand necessary?
It contains a calibrated orifice and matching flow chart for that orifice.
It is manufactured to accepted testing standards.
Test results can be traced to the specific test stand used for the test if there are concerns about accuracy.
When the dry bulb temperature increases, the relativity humidity of air:
Decreases
When the dry bulb temperature increases, the wet bulb temperature:
Increases
When the dry bulb temperature increases, the dew point temperature:
Remains the same
When the dry bulb temperature increases, the specific humidity:
Remains the same
When the dry bulb temperature increases, the specific volume of the air:
Increases
When the dry bulb temperature increases, the density of air:
Decreases
There are _________ grains of water vapor per pound of water.
7,000
There are _________ pounds per cubic foot of air.
.075
The cfm per ton rate for normal comfort cooling is approximately:
400 cfm/ton
Cooling air raises its:
Relative humidity
Air with a dry bulb temperature of 60 degrees and a wet bulb temperature of 60 degrees has a relative humidity of:
100%
Air with a dry bulb temperature of 60 degrees and a wet bulb temperature of 60 degrees has a dew point temperature of:
60 degrees
Decreasing the cfm over an evaporator will _______ the moisture removal from the air.
increase
A rotating velometer measures:
feet
Return air grilles are not to be installed in:
Bathrooms or kitchens
The proper amount of air in cfm for each room is determined by:
A detailed room-by-room heat load calculation
On residential duct installations the accepted method of attaching duct sections to each other is:
Using the slip and drive method
Which of the following is not an acceptable location for a thermostat?
5” off the floor on an outside wall
What is the difference between accuracy and precision when applied to instruments?
Accuracy is a measure of how close the measurement is to being correct. Precision is the measure of how small a value the instrument can detect.
The range of an instrument is the:
difference between the lowest and highest readings the instrument can measure
difference between the lowest and highest readings the instrument can measure
4,000 cfm
A 32” by 32” square duct is to be changed to a height of 28” so it will fit around an obstruction in a boiler room. How wide must the duct be in order to maintain the same area? Round the number off to the nearest whole number of inches.
37”
(T/F) The greater the velocity, the more resistance there is to a change in direction.
T
(T/F) If the duct area decreases, the velocity increases.
T
(T/F) When a fitting creates turbulence, the turbulence continues for several feet down the duct.
T
A 24” by 8” rectangular duct has an aspect ratio of:
3:1
The most efficient method of air balancing a duct system is the:
proportional method
Which of the following types of turning vanes produce the least dynamic system loss?
Single wall vanes
Which equations is used to determine the actual operating capacity of a system?
Btuh = 4.5 × cfm × the difference in enthalpy between the return and supply air
What is known as the “silent killer”?
Carbon monoxide
___________ ventilation is a control strategy used to maintain a high oxygen content in buildings where a healthy environment is of particular concern.
Demand
The most economical means of measuring the amount of oxygen deprivation in an occupied space is through the use of a:
carbon dioxide sensor
What is the natural result of combustion?
Carbon dioxide, Water vapor, Carbon monoxide
The most serious result of incomplete combustion in any fuel-burning heating device is:
Carbon monoxide
Carbon monoxide poisoning is often mistaken for:
The flu with a headache
Carbon monoxide is measured in:
PPM
Outdoor air intake dampers should be located away from:
Busy ground level intersections
Loading docks
Sewer vents
Infiltration is air that:
enters a space without filtration or control
Offgassing is:
The release of volatile compounds from products and construction materials
Usually harmful compounds and chemicals, which slowly enter living spaces over time
Chemicals released into the air especially as the host material is heated
In the science of indoor air quality VOC stands for:
Volatile Organic Compounds
Which of the following are common symptoms of carbon monoxide poisoning?
Headache and nausea
Fatigue and dizziness
Shortness of breath
Nitrogen dioxide is a toxin resulting from:
Both the process of combustion and rapid oxidation
(T/F) The quality of air indoors can often be worse than that of the outdoors.
True
Mitigation means to:
alleviate
Solid particles suspended in air are measured in:
Parts per million
Which of the following organizations has legal oversight over air quality in the United States?
EPA
The higher the velocity of the air through a fiber filter, the:
Less effective the filtration
At what level of indoor air carbon monoxide do most fire departments require emergency personnel to wear self-contained breathing apparatus (SCBA)?
50 ppm
The function of an ERV is to:
Exchange heat between exhaust and intake air
ASHRAE standard 55-1992 specifies the conditions likely to be thermally acceptable to _______ of adult occupants of a conditioned space.
75%
Indoor air quality is legally the responsibility of:
The building owner
The business leasing the building
Those operating and maintaining the building
Clean rooms are classified according to:
The particle count per cubic foot of air
HEPA stands for:
High Efficiency Particulate Air filter
The internal static pressure in a building should be approximately:
.05” higher than the outside air pressure
Activated charcoal is often satisfactory for the removal of:
Gas-phase toxic or odorous pollutants
A __________ biological safety cabinet is a gastight negative pressure containment system that provides a physical barrier between the agent and the worker.
class 3
Is refrigerant oil that has gone through a compressor burn-out classified as a toxic waste?
Yes, if the oil contains a substance classified by the EPA as a toxic waste.
Three common methods used to mitigate poor indoor air quality are:
Filtration, ventilation, and exhaust
A micron is:
One 25,400th of an inch
Bacteria, molds, pollen, and viruses are types of:
Biological contaminants
According to the World Health Organization approximately what percentage of buildings suffer from SBS (Sick Building Syndrome)?
30%
A key factor in solving indoor air quality problems is to:
Locate and isolate the source of the pollution
Which of the following would be the first step in the process of investigating an indoor air quality problem at a building?
Defining the perceived problem
Physical stressors are those factors that:
Can be sensed, felt, seen, or heard
Sick Building Syndrome is highly suspected when:
20% or more of the building occupants complain with physical symptoms within a 2-week period.
A high degree of occupants call in sick with symptoms of headaches, fatigue, dizziness, coughing, nausea, and eye or throat irritations.
A high degree of occupants find that their symptoms are alleviated by leaving the building.
During an initial pre-investigatory building walk-through, which of the following measurements may be taken?
Carbon dioxide, temperature, and relative humidity readings
What gas originates from manmade materials within a building?
Formaldehyde
What can affect the intensity of a person’s reaction to an irritant in the air?
Temperature and humidity
A fairly common but not regularly recognized source of poor indoor air quality and increased dust and residue in homes is:
The use of candles
What substances has been directly attributed to as many as 20,000 cases of lung cancer in the United States?
Radon gas
Concentrations of radon gas is measured in:
picocuries
Particulates are categorized in terms of:
Size and source
Excessively high concentrations of carbon dioxide in indoor air is usually an indication of:
A lack of ventilation air
Which of the following IAQ problems was first discovered to have its source in HVAC cooling towers?
Legionnella
Organic compounds are:
Compounds that contain carbon
A compound is a:
material made up of two or more elements electrically bound to one another
TLV stands for:
Threshold limit value
The average urban outdoor air concentration of carbon dioxide has been determined to be:
40 ppm
