1. Chapter 3B: INDOOR AIR QUALITY
Agami Reddy (rev-Dec 2018)
Importance of IAQ
Indoor air contaminants
Air quality standards
Types of ventilation methods and control
Ventilation standard- ASHRAE Standard 62.1
Ventilation of fully mixed spaces
Air distribution efficiency
Filtration cleaning of air
Sick Building Syndrome
HCB-3 Chap 3B: IAQ

2. Importance of IAQ Poor IAQ has large associated costs
- Productivity loss due to decreased comfort
- Health costs
- Litigation
Article by Fisk, ASHRAE Journal May 2002
US national health and productivity benefits from improved IEQ (air, thermal, lighting)
Health: $17 – 48 billion per year (respiratory diseases. Allergies, asthma,…)
Productivity loss: $20 – 160 billion/yr (US GDP in 2003 was $10.4 trillion)
HCB-3 Chap 3B: IAQ

3. Indoor Air Contaminants
Building material emissions
Equipment emissions
Dust
Human, animal and insect by-products
Toxins and allergens from microbial growth
Airborne pathogens
Chemicals, household, industrial
Outdoor contaminants drawn into building
HCB-3 Chap 3B: IAQ

4. http://www.kaycee.net/mold/index.html http://www.epa.gov/iaq/molds/
moldresources.html
HCB-3 Chap 3B: IAQ

5. Outdoor Air Quality Standards
EPA: National Ambient Air Quality Standards
NIOSH and OSHA
NIOSH- National Institute for Occupational Safety and Health
OSHA- Occupational Safety and Health Organization
HCB-3 Chap 3B: IAQ

6. Fig. 3.15 Characteristics of particulate matter
and cleaning equipment suitable for removing it
HCB-3 Chap 3B: IAQ

7. Indoor Quality Standards
HCB-3 Chap 3B: IAQ

8. Types of Ventilation Methods (Dilution)
Local ventilation preferred for point source contamination
- Results in lower airflow requirements
- Source is better contained
General ventilation preferred for distributed contamination
- Provides simultaneous control of temp., humidity, odor
- Usually done by all-air or air-water air-conditioning systems
HCB-3 Chap 3B: IAQ

9. General Ventilation: Two limiting cases
Dilution ventilation
Ventilation air mixes “perfectly’
With air in space
Displacement ventilation
Plug flow (i.e., like a piston from
inlet to outlet)
- Air is freshest near inlet
Gradually gets contaminated
Lower space is the breathing zone
HCB-3 Chap 3B: IAQ

10. HCB-3 Chap 3B: IAQ

11. ASHRAE Standard 62.1-2013 (Dilution ventilation)
The purpose of this standard is to specify minimum ventilation rates and indoor air quality that will be acceptable to human occupants and minimize the potential for adverse heath effects
This standard is intended for regulatory application (new, existing buildings)
This standard is intended to be used to guide the improvement of indoor air quality in existing buildings
HCB-3 Chap 3B: IAQ

12. ASHRAE Standard 62.1 Two methods for compliance
- Ventilation rate procedure (prescriptive)
OA intake rates determined based on space/application, occupancy level and floor area
for typical contaminant sources and strengths
- IAQ procedure (performance)
requires monitoring certain contaminants,
ventilation modulated accordingly for control
(additional costs: sensor, control accuracy)
Potential for saving energy (demand ventilation based on CO2)
HCB-3 Chap 3B: IAQ

13. ASHRAE Standard 62.1 (2013)
Required outdoor air needed to be supplied to breathing space
Breathing zone (region between 3 – 72 inches above the floor and more than 2 ft from walls or fixed A/C equipment)
where
breathing zone airflow rate (cfm or L/s)
RP and Ra air flow rates per person and per floor area
PZ and AZ number of occupants and total floor area
HCB-3 Chap 3B: IAQ

14. HCB-3 Chap 3B: IAQ

15. 637 L/s
HCB-3 Chap 3B: IAQ

16. Ventilation of Fully Mixed SpacesCo Vo Ci Vo
Npol
HCB-3 Chap 3B: IAQ

17. Case (i) Air Distribution Efficiency- Single Zone
Air Distribution or air mixing in a room is usually not perfect
- One way of treating this for a room with
overhead air distribution is to assume the
room to be stratified vertically into
two uniformly mixed zones
Certain fraction S of the supply air stream bypasses the occupied zone (this factor is also called the “occupied zone by-pass factor” or the “stratification factor”)
Because of stratification some of the outdoor air is exhausted without performing any useful reduction in the contaminants of the occupied zone
HCB-3 Chap 3B: IAQ

18. Ventilation effectiveness is the fraction of outdoor supply air which is “utilized” by occupants
HCB-3 Chap 3B: IAQ

19. Expression for ventilation effectiveness in terms of bypass
fraction S and recycle fraction R when no filters present:
HCB-3 Chap 3B: IAQ

20. Case (ii) Building with two zones served by a single VAV HVAC system
Another correction to the minimum ventilation air amount is suggested by ASHRAE standard for VAV systems
Multiple spaces may have different ventilation requirements.
Further, the thermal loads in these spaces would vary over the year and often by different amounts.
Since the single duct supply systems carries the entire supply air amount (ventilation plus recycle), supply air to the individual zones may not contain the required ventilation air amount
One would have to increase the amount of outdoor air so as to meet the needs of the most critical zone,
This results in large energy penalty due to over-ventilation of the other zones.
HCB-3 Chap 3B: IAQ

21. Removing Contaminants from Air-Stream
Gaseous elements:
- Absorption
- Physical adsorption (activated charcoal)
Particulate: Filtering
Particulates or suspended particles come in a wide range of sizes, shapes and concentration. Different types of filters used.
Three operating characteristics of filters:
- Efficiency- ability to remove particles
- Air flow pressure drop- affects fan power and energy consumption
- Dust holding capacity- determines how often a filter should be cleaned or replaced
HCB-3 Chap 3B: IAQ

22. Figure 3.17 Efficiency of removing particles versus particle size, for several filter types. These curves are approximations based on manufacturers' data. They do not correspond to results of tests recognized by ASHRAE and should not be used for HVAC design. (Courtesy of ASHRAE, Standard :
HCB-3 Chap 3B: IAQ

23. Sick Building Syndrome (SBS)
Definition:
Significant fraction of building occupants experience acute discomfort and health related ailments (sensory irritation of eyes, nose, throat and skin),
Linked to time spent in a building (symptoms diminish when not in building), but no specific illness or cause can be identified
HCB-3 Chap 3B: IAQ

24. Sick Building Syndrome (SBS)
Causes:
Internal chemical contaminants: usually air pollutants (indoor/outdoor)
Volatile organic compounds, including formaldehyde, cleaning products, manufactured plastic and wood products
Ozone from photocopiers and printers
Carbon monoxide, carbon dioxide and other inorganic oxides given off as combustion products in heating systems
Small fibers from furnishings, regularly agitated into the air by frequent sweeping. Also, asbestos in older buildings
Tobacco smoke
Poor ventilation
Moisture: High humidity, molds, spores
Personal: gender, allergic
Psychological: mass psychology, job dissatisfaction/stress
HCB-3 Chap 3B: IAQ

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26. Figure 3.18 Predicted trends in illness or sick leave as a function of ventilation rate.
HCB-3 Chap 3B: IAQ

27. Sick Building Syndrome Resolution
Proper material selection (avoid VOC)
Increase ventilation
Proper smoking policy
Proper location of exhausts and air intakes
Resolve moisture problems
Replace contaminated materials
Remove contaminant traps (carpet)
Implement proper maintenance practices
Education of occupants
HCB-3 Chap 3B: IAQ

28. Outcomes Understanding importance of indoor air quality
Familiarity with possible sources and effects of indoor air contaminants
Familiarity with outdoor and indoor air quality standards
Knowledge of different types of ventilation methods, both local and general, and how they dilute and limit contaminants
Knowledge of the different types of air filters
Be able to calculate ventilation requirements based on ASHRAE 62 standard
Understanding of analysis methods involving one-zone and two-zone models of indoor spaces
Understand concept of ventilation effectiveness
Familiarity with causes and remedies of sick building syndrome
HCB-3 Chap 3B: IAQ