SECTION 6
AIR CONDITIONING (HEATING
AND HUMIDIFICATION)
UNIT 34
INDOOR AIR QUALITY
UNIT OBJECTIVES
After studying this unit, the reader should be
able to
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List sources of indoor air pollution.
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Explain procedures for eliminating contamination sources.
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Describe how molds reproduce.
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Discuss ventilation as it applies to indoor air quality.
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State two substances needed for mold to grow.
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Describe air cleaning devices.
UNIT OBJECTIVES
After studying this unit, the reader should be
able to
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Discuss reasons for cleaning air ducts.
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Explain relative humidity.
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State reasons for providing humidification in winter months.
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Describe various types of humidifiers.
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State reasons for installing self-contained humidifiers.
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List general factors used when sizing humidifiers.
INTRODUCTION
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Indoor air is often more polluted than outdoor air
Many people spend as much as 90% of their time indoors,
especially the very young, the very old and the ill
ASHRAE Standard 62-2001 determines the acceptable indoor
air quality levels
SOURCES OF INDOOR AIR
POLLUTION
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There are many indoor air pollutants
Older homes allow pollutants to enter
Newer structures are tighter
Outside air must be brought into the structure
Inadequate ventilation can cause
– Window and wall condensation
– Formation of mold and smelly, stuffy air
CONTROLLING INDOOR AIR
CONTAMINATION
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Eliminate the source of the contamination
Provide adequate ventilation to the structure
– Adds and removes air from the structure
– Contaminants are removed while fresh air is introduced to
the structure
– The contamination concentration is reduced
Provide a means to clean the air
CONTROLLING INDOOR AIR
CONTAMINATION
COMMON POLLUTANTS
• Radon
• Tobacco smoke
– Second-hand smoke
– Contains over 4,000
components
• Biological contaminants
– Dust mites
– Mold
• Lead
– Air, water, food, soil
• Household products
– Contain organic chemicals
– Paint, varnish, cleaning
products
• Formaldehyde
• Pesticides
• Asbestos
• Pollutants from combustion
– Burning fuels
– Carbon Monoxide
CONTAMINATION SOURCE
DETECTION AND ELIMINATION
Various monitoring instruments can detect:
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Carbon dioxide
Carbon monoxide
Hydrogen sulfide
Sulfur dioxide
Chlorine
Hydrogen
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Oxygen
Nitric oxide
Hydrogen Cyanide
Ammonia
Ozone
Hydrogen chloride
VENTILATION
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Process of supplying/removing air from an area
Proper ventilation improves air quality
Outside air must be filtered and heated or cooled
Ventilation methods can be natural or mechanical
Residences typically have natural ventilation
ASHRAE Standard 62-2001
Energy Recovery Ventilators (ERV)
Heat Recovery Ventilators (HRV)
HEAT RECOVERY VENTILATOR (HRV) CONFIGURATION
Air to occupied
space
Intake blower
Intake filter
Fresh air
intake
Exhaust
Air from occupied
space
Exhaust
blower
Exhaust
filter
Heat exchanger
Structure wall
AIR CLEANING
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Mechanical filters
– Fiberglass disposable, pleated, cube, pocket, HEPA
Electronic air cleaners (Multi-stage)
– Pre-filter, ionizing, collection, odor removal
Ion generators
– Charge particles that then adhere to walls and floors
Ultraviolet light (UV-C)
– Destroys microbes that create unhealthy air
Permanent steel or
aluminum filter
Fiberglass disposable filter
Pleated filter
TYPICAL ELECTRONIC AIR CLEANER STAGES
Prefilter
Large particles
captured here
Charging
section
Particles are
charged here
Collection
Charcoal
Small particles are
collected here
Odors are removed
here
DUCT CLEANING
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Ducts should be cleaned if there is visible mold growth, rodent infestation
or excessive dust
Cleaning includes the ductwork, grilles, diffusers, heat exchangers, coils,
condensate pans, fan motors, motor housings and humidifier components
Vacuum duct cleaning systems are vented outside
Access holes must be resealed upon completion
National guidelines should be followed
AIR HUMIDIFICATION
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Relative humidity is the percentage of moisture in the air compared to
the maximum capacity of an air sample to hold moisture
Relative humidity falls as temperature increases
– Air expands when heated and moisture is spread out
– 1 ft3 of air can hold more moisture at higher temps.
Recommended humidity for homes is 40 to 60%
People can be comfortable at lower temperatures if the humidity is
higher
HUMIDIFIERS
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Evaporative humidifiers – use a wet media
– Air is passed over the media and the water evaporates
Electrically heated humidifiers
– Water evaporated by electric heating elements
Infrared humidifiers –
– Uses infrared lights reflected onto the water
Atomizing humidifiers
– Discharges tiny water droplets into the air
SIZING HUMIDIFIERS
1.
2.
3.
4.
The number of cubic feet of space to be humidified.
The construction of the building. This includes quality
The amount of air change per hour and the approximate
The level of relative humidity desired.
INSTALLATION
• Particular attention should be given to clearances within the duct or
plenum.
• If mounting on a supply duct, choose one that serves the largest
space in the house.
• Plan the installation carefully, including locating the humidifier, as
already discussed, and providing the wiring and plumbing (with
drain).
• Always check state and local building codes.
UNIT SUMMARY
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ASHRAE standard 62-2001 determines acceptable indoor air quality levels
Air quality can be improved by removing the source of contamination,
filtering and ventilating
Duct systems should be cleaned if there is excessive dirt, infestation or
mold growth
Relative humidity is the ratio of moisture in an air sample divided by the
capacity of the air to hold moisture
Humidifiers add moisture to the air in the structure