1111 Ch 27, 28, 29, 30 Study Guide

Dust particles are usually ____ microns in size.

1-200 microns

If air flows through an occupied space at more than ____, occupants of the space will feel a draft.

15′ to 20′ per minute (4.5 m/min to 6 m/min)

If the pressure drop across a disposable air filter is more than ____% of the pressure drop across the fan, the air filter should be changed.

25

The maximum air movement within a room is generally limited to ____ to prevent discomfort to the occupants.

25 fpm

Air velocity greater than ____ fpm at a register may result in a draft.

500

The desirable temperature for human comfort is ____.

72°F (22°C)

The human comfort level for summer is about ____ and 50% rh.

75°F (24°C) db

Air filters should be changed at approximately ____ of design final resistance.

80%

Ultraviolet lamps should handle _____ of the bacteria in residential and commercial systems.

80-90%

A standard that includes equipment and system requirements and minimum ventilation rates that result in acceptable indoor air quality is ____.

ASHRAE Standard 62

Soft fabrics, such as drapes, curtains, and fabric-covered furniture, are generally noise ____.

Absorbers

Tools that allow a technician to create a point in the HVAC system from which to inspect and clean are ____.

Access Tools

An instrument used to measure the total airflow of a central HVAC system is a(n) ____.

Air Handler Flowmeter

Which of the following statements about damper controls is false?

All automatic dampers open and close based on the pressure of the conditioned air.

Fans used in air distribution systems ____.

Are usually axial flow or radial flow

A naturally occurring mineral that forms fiber bundles is ____.

Asbestos

The ____ test measures the ability of an air filter to remove atmospheric dust by evaluating the flow rates on both sides of the filter and measuring the quantity of material it captures.

Atmospheric dust spot efficiency

Which of the following statements about air pressure is false? A. Air pressure at the earth's surface is due to the weight of moisture above the earth. B. Air pressure increases as altitude increases. C. Air presses against the earth at sea level with a pressure of 14.7 psi (101 kPa). D. None of the above.

B. Air pressure increases as altitude increases.

____ are simple, single-cell microorganisms that are responsible for many diseases.

Bacteria

Ultraviolet lights are frequently installed in ductwork to reduce ____.

Bacteria, Mold Spores, and Viruses

Airborne microorganisms, such as viruses, fungi, mildew, and yeast, are called ____.

Bioaersols

Which of the following is not a step used when balancing a system?

Block all dampers in the ducts and at each room supply.

A(n) ____ test shows how effectively the building envelope minimizes the amount of unconditioned air passing through into conditioned space.

Blower Door

Odors and vapors can be removed from the conditioned space ____.

By cooling some gases to their condensation or freezing temperature Through oxidation or ultraviolet light treatment With activated charcoal or by combining them with other chemicals All of the above.

Which of the following statements about air ducts is true? A. Square ducts are more efficient and reduce resistance to airflow. B. Round ducts conform better to building construction than square or rectangular ducts. C. Air ducts may be made of galvanized sheet metal. D. Air ducts must be made of materials with a great deal of pliability.

C. Air ducts may be made of galvanized sheet metal.

Which of the following statements about airflow in duct systems is false? A. The more abruptly the airflow changes direction, the more turbulent it becomes. B. Turbulence can be minimized in changes of direction by installing long-radius elbows. C. Airflow compression will be reduced through the use of additional 90° elbows. D. Built-in directional vanes can be used to minimize turbulence.

C. Airflow compression will be reduced through the use of additional 90° elbows.

Which of the following statements about duct systems is false? A. Ducts should be insulated if the duct system is installed in an unvented attic. B. In basements, ducts can be run across and just under the first floor's floor joists. C. Ducts in concrete are made by drilling airways with large drill bits and hole saws. D. Ducts may be installed in basements, crawl spaces, and concrete floors.

C. Ducts in concrete are made by drilling airways with large drill bits and hole saws.

Which of the following statements about fire dampers is false? A. The two general types of fire dampers are static and dynamic. B. Fire dampers are designed to close automatically on detection of heat. C. Static systems require fire dampers at locations in which fan pressure will be on during a fire. D. Ducts passing through a firewall must have fire dampers.

C. Static systems require fire dampers at locations in which fan pressure will be on during a fire.

A(n) _____ filter is often used in refrigerators because of its ability to reduce odors.

Carbon

____ filters use an activated-charcoal form to remove solid particles, odor-causing gases, and bacteria.

Carbon

A deadly, odorless, colorless gas that leaves a metallic taste in the mouth describes ____.

Carbon Monoxide

OSHA describes sick building syndrome as a reaction to ____ stimuli.

Chemical, Physical, Biological

The conditions that are normally maintained in an indoor space are known as the indoor ____.

Climate

The long-term weather trends for a region are known as the ____.

Climate

One step in preparing a house for blower door testing is to ____.

Close exterior windows and doors

The arcing lines on a psychrometric chart represent the ____.

Constant relative humidity levels

The vertical-slanted lines on a psychrometric chart represent the ____.

Constant specific volumes

Which of the following principles applies when designing a duct system for a building? A. Locate the air handler in a central location. B. Keep duct runs as short as practical. C. Install ducts off the sides of a plenum, not off the end. D. All of the above.

D. All of the above.

Which of the following statements about duct systems installed in concrete is false? A. Ducts installed in a concrete slab are usually made of metal, plastic, or ceramic. B. The ductwork can be laid out and the slab poured over it. C. The branch ducts usually connect to a perimeter duct that has diffusers installed at intervals along the floor. D. Upflow furnaces are used with this type of installation.

D. Upflow furnaces are used with this type of installation.

Smoke from smoke sticks, smoke guns, or smoke candles can be used to ____.

Determine the amount and direction of a draft Check air movement Locate air leaks All of the above.

____ is the temperature below which water vapor in the air will start to condense.

Dew Point

The vertical lines on a psychrometric chart indicate ____.

Dry-bulb temperature

An instrument used to pressure test a central HVAC system's ductwork is a(n) ____.

Duct Blaster

combined effect of dry-bulb, wet-bulb, and air movement that provides an equal sensation of warmth or cold

Effective Temperature

total heat content in an air sample, sensible and latent heat

Enthalpy

During the heating season, warm air rises and ____.

Escapes through the upper surfaces of the building, Raises the pressure in the upper areas of the building, Lowers the pressure in the bottom parts of the house, all of the above

A natural passage of air leaving a building through doors, windows, and other construction joints is referred to as ____.

Exfiltration

The ____ is the outermost layer of the earth's atmosphere.

Exosphere

An instrument used to measure the airflow through a duct at a given supply or return is a(n) ____.

Flow Hood

____ is an advanced technique used to measure air filter performance in which extremely accurate equipment is used to count the number of particles trapped by the filter and also classify the particles by size.

Fractional Efficiency

Small solid particulates suspended in air and formed by the condensation and solidification of gaseous materials are called ____.

Fumes

____ filters remove 99.97% of particles in air passing through.

HEPA

If the rooms in a building are tightly sealed, the ____.

HVAC system should be designed to admit fresh air into the building, amounts of carbon dioxide, water vapor, and various impurities will increase, level of oxygen will decrease and eventually be exhausted, All of the above.

Dirt buildup on fan motors can cause ____.

Increased operating temperatures Fan motors to draw more current than usual Eventual motor failure All of the above.

A natural exchange of air through leakage into a building is known as ____.

Infiltration

When an atom has an imbalance of electrons and protons, the atom is ____.

Ionized

During the cooling season, cold air ____.

Is replaced by warm air at the upper levels, Tends to flow downward, May leave the building at the lower levels, all of the above

Which of the following statements about an Evaporative cooling system is false?

It decreases the rh level of the air while raising its db temperature.

The heat released when moisture condenses out of the air is ____ heat.

Latent

The growth of minute fungi that forms on vegetable and animal matter describes ____.

Mold

If there is more return air than supply air in a room, the room will have a ____ pressure.

Negative

Which of the following statements about air distribution systems is false?

Negative pressure in a building decreases the infiltration at windows and doors.

A ventilation system is usually designed to allow the air filter pressure drop to be about ____ of the total pressure drop.

One-Fourth

Air with a relative humidity of 25% contains ____ of the moisture it is capable of holding.

One-fourth

____ filters use an electrostatic charge that is produced by the friction of air blowing across the fibers in the filter.

Passive Electrostatic

Small particles released by plants as part of their reproductive cycle are referred to as ____.

Pollen

Air delivered to a room from a supply duct is called ____.

Primary Air

is the science of studying the thermodynamic properties of air and water vapor

Psychometry

measures dry-bulb and wet-bulb thermometers to determine relative humidity

Psychrometer

The science of studying the thermodynamic properties of air and water vapor is called ____.

Psychrometry

An odorless, radioactive, inert gas that is formed from the natural decay of uranium describes ____.

Radon

Which of the following is a gaseous pollutant?

Radon

The ____ is the amount of heat that affects the air temperature compared to the total heat added to or released from the air.

Sensible heat ratio

____ is/are composed of solid particles carried into the atmosphere by gaseous products of incomplete combustion.

Smoke

Diffusers in air distribution systems ____.

Spread the air leaving the duct more uniformly than registers

The outer tube of a pitot tube has holes on the side and measures only the ____ pressure.

Static

The ____ is the layer of the atmosphere that contains the ozone layer.

Stratosphere

A ____ anemometer operates on the principle that incoming air will cause a deflection at different angles as the air velocity changes.

Swinging-Vane

____ anemometers can be used in environments where electronic meters pose an explosion risk.

Swinging-Vane

The ____ is the layer of the atmosphere that is closest to the earth.

Troposphere

Heat recovery ventilators (HRVs) ____.

Use a fan to bring in fresh air from the outside

A ____ anemometer measures airflow velocity using a small propeller.

Vane

The difference between the total pressure and the static pressure is the ____ pressure.

Velocity

The volume of air flowing through a duct is calculated by multiplying air ____ by the cross-sectional area of the duct.

Velocity

Automatic fire dampers should be installed in all ____ ducts in commercial and industrial buildings.

Vertical

Air pressure for the sake of air velocity is measured in inches of ____.

Water

Areas where Mold can start to form

Water spray systems, Humidifiers, Wet porous surfaces

Carbon monoxide is _____.

a result of incomplete combustion of fuel

Ultraviolet lights ____.

are harmful to the eyes

Latent Heat changes

the level of humidity in the air

Sensible Heat changes

the temperature of the air

An ERV is ____.

used where humidity control is important