1. WHAT IS CONSIDERED AN "EFFECTIVE" AIR CLEANING DEVICE?
- R Shaughnessy, PhD1
- R Sextro, PhD
1 Indoor Air Program, University of Tulsa, USA
Ph:
April ’06 JOEH

2. National Expenditures for IAQ Problem Prevention or Mitigation (LBNL – 58694, June 2005)
$15.9 billion annual business (range $12-20 billion)
Air clng and improved filtration………$1.5 billion
IAQ Consultant services……………….$2.1 billion
Building Remediation………………….$3.4 billion
Duct Cleaning…………………………..$ 4 billion
Asbestos/lead abatement……………….$ 4 billion
IAQ litigation/insurance………………..$500 million
Radon Mitigation……………………….$200 million
Certification/labeling……………………$100 million
Laboratory Services…………………….$100 million

3. Misleading Ads
“Removes virtually any contaminant including gases and VOCs”
“Relieves asthma and allergies”
“Eliminates allergies and other
maladies caused by molds”
Eliminates almost 100% of such harmful airborne particulates as dust, bacteria, viruses, pollen, mold, spores, tobacco, and general room odors”

4. Dispelling Common Myths
Ozone Generators
Significant exposure to ozone and reaction byproducts
California DHS warning
FTC lawsuit
House Plants
Recirculating Range hoods
Desktop Air Cleaners

5. Particle Characteristics of Allergens
SETTLING RATE
Rapid (e g, 20 micron particle falls 1 meter in about 80 seconds)
Fines settle slowly (e g, 0.2 micron particle falls 1 meter in about 5 days)
Rapid
Varies
Negligible
TYPE
Dust Mite
Cat/Pet Dander
Cockroach
Common Fungal Spores
Plant Pollen
ETS
SIZE RANGE (micron)
10-35
<2 to >10
80% >10
2-10
15-25
Mean ~ 0.2
Particle must be airborne long enough for air cleaner to have any effect

6. Sizes of biological particles
1 micrometer
Pollen
House dust mite allergens
Fungal spores
Cat allergen
Bacterial
cells and spores
Viruses

7. Historical Perspective on Portable Air Cleaners
(1) Peshkin, M.N., and Beck, I. (1930), “New and Simplified Mechanical Air Filter in the Treatment of Hay Fever and Pollen”, J.Lab & Clin. Med. 15; 643.
(2) Crisp, L.H., and Green, M.A., (1936), “Air Cleaning as Aid in Treatment of Hay Fever and Bronchial Asthma”, J. Allergy, 7:
(3) Kranz, P., (1963), “Indoor Air Cleaning for Allergy Purposes”, J. Allergy, 34:155.
(4) Tuffley, R.E., and Zorab, P.A., (1964), “Portable Air Purifier”, Lancet, 41:415-6.*
* Use of cellulose & asbestos blended filter for
patients w/ bronchitis and asthma

8. Air Cleaning Technologies
Particle Removal
Filters
Electrostatic Precipitators (ESP)
Ionizers
Gas Removal
Adsorbents
PCO

9. Electrets Polymeric extruded fibers with built-in charge Advantages
Low pressure drop
Higher initial efficiencies due to inherent charge
Disadvatages
drop in efficiency during the loading life cycle once installed in an ambient airstream
VOCs or super-fine nanoparticles, can neutralize the fiber charge reverting the media to the lower efficiency levels of non-electret media

10. Owen, M.K., et al., 2003

11. Hanley, J., et al., IA ‘99

12. Electrostatic air cleaners (electronic, or electrostatic precipitators)
Basic design
Ionizing plate

13. Electronic air cleaners- ionizing plate
Principle of operation

14. Electronic air cleaners
Advantages
High initial efficiencies; No pressure drop
Disadvantages
Produces ozone unintentionally
Requires frequent cleaning to maintain efficiency
EAC slowly loses its ability to charge particles due to build-up of silicone deposits on the electrical ionizing grid wires (Hanley, et al, 2003)

15. Ionizers Rely on generation of - ions
Particles are charged and attracted to surfaces (plate-out/soiling)
Some configurations draw charged particles back to unit for collection
Poor performance historically
Ozone production
Concern over breathing charged particles

16. Portable Air Cleaners 3 out of every 10 households now own P.A.C.
Effectiveness limited by flow rate and efficiency of collection
Primarily for cleaning air in a single room
Components must be replaced or cleaned periodically
Noise factors
Advertisements are inundated with hype
AHAM ratings for particle removal

17. Air Cleaner Led to Improvement in Health
One-third report that their use of an air cleaner has led to an improvement in their health / health of other household members.
Base: Total returns (n=936). Source: Q50. Has use of an air cleaner led to an improvement in your health or the health of other household members?

18. Health benefits from Portable Air Cleaning
Studies far from definitive
Studies to date failed to separate effects of air clng from the effects of applied source control measures (i.e. allergen-proof bed encasings, washing pets, excl. pets from home, etc)
Well-designed studies needed; must include:
proper controls
clinical evaluation
rigorous control/reporting of relevant environmental variables (National Academy of Sciences, 2000, Eggleston, et al. 2001)

19. Type of Air Cleaner
Half own a HEPA filter air cleaner, while one fifth own a machine with an electrostatic filter or electrostatic precipitator.
One-quarter are not sure about the type of air cleaner they own.
Base: Total returns (n=936). Source: Q20. What type of air cleaner do you own?

20. AHAM Standard AC-1, 2006 AHAM testing of air cleaners in the U.S.
AHAM standards are presented to the American National Standards Institute (ANSI) for recognition as American National Standards
Testing for removal of particulate (smoke, dust, pollen)
Uses CADR model to evaluate performance of air cleaners
And from these figures calculate room size suitability (CADR x 1.5)
Clean Air Delivery Rate (CADR) is the amount of “equivalent cleaned air” provided by an air cleaner

21. What is industry accepted value What is reasonable What is achievable
What is the minimum Effective Cleaning Rate, CADR, required to impact an indoor environment?
What is industry accepted value
What is reasonable
What is achievable
What does technology afford us
Strive for highest removal possible
International perspective

22. With and Without Air Cleaner Pollution vs. Time (Showing 80% Reduction)
The AHAM recommendation for room size for a given CADR will result in an 80% reduction in ambient levels of particulates as the challenges vary throughout the day

23. Modeling the Indoor Environment Assumptions:
air concentrations of contaminants well-mixed
change in contaminant conc’n described by 1st order differential equation

24. Mass Balance Equation:
(1) .
Where:
S is the emission rate in mass per unit time
V is the volume of the indoor space
λν is the air infiltration rate (in units of inverse time)
P is the penetration factor
Co is the outdoor contaminant concentration
Ci is the indoor contaminant concentration
Λ represents all first order removal processes (in units of inverse time)

25. To be effective on contaminant removal, the air cleaner must compete with:
Surface deposition
Ventilation (outdoor air exchange)
With vapor-phase contaminants, rate of indoor rxns must be considered

26. Effectiveness, ε, has been defined by Nazaroff (2000) as the difference in indoor concentration due to air cleaning compared to the "no-cleaning" case; rearranging above equations ε can be expressed as:
(7) .
The closer the effectiveness is to 1, the more ideal the performance of the air cleaner is in removal of the contaminant

27. Figure 1. Effectiveness of airborne contaminant removal as a function of the ratio between air cleaner performance and the other removal processes, ventilation and deposition (for particles) (adapted from Nazaroff, et al., Healthy Buildings 2000)

28. Relationship between CADR, room size (ft2), (assuming 8 ft ceiling), 80 % removal (small particles)

29. Figure 2. Clean Air Delivery Rate as a function of indoor area for effectiveness value of 80% as recommended by AHAM; graph applies to removal of smaller particles, less than ~1 micron in size (Shaughnessy & Sextro, submitted, 2005).

30. As λd increases, the effectiveness (ε)
Recall that:
As λd increases, the effectiveness (ε)
afforded by the air cleaner decreases

31. Figure 5. Particle removal by deposition as a function of particle size.”Small” refers to the particle size region associated with the peak in the ETS mass distribution; “medium” refers to the size region associated with some allergens and with larger ambient aerosols; and “large” refers to the size region associated with pollens & sources of asthma-related allergens such as dust mites.
Thatcher, et.al. (2002) and Xu, et.al. (1994), as reported by Fisk, et.al. (2002)

32. Figure 3. Clean Air Delivery Rate as a function of indoor space area and particle size. Volume is based on a ceiling height of 8 ft. CADR-80, -67, and -50 are, respectively, the CADR values based on 80 %, 67% and 50% reduction in particle concentrations due to air cleaner operation. (Shaughnessy & Sextro, submitted, 2005).

33. NAS, Clearing the Air Report (2000): Limited evidence indicating that particle air cleaning is associated with a reduction in the exacerbation of asthma symptoms…. suggest that air cleaners are most likely to be effective in reducing indoor concentrations of particles smaller than 2 microns…. much of the airborne allergen appears to be within larger particles”

34. Selecting a Portable Air Cleaner
based on room size
noise factors
typically good for
particulates only
not whole house
look for CADR of
between
(AHAM rating); % effectiveness minimum for room size

35. Ozone Standards EPA NAAQS: 80 ppb average over 8 hours
OSHA PEL: 100 ppb average over 8 hours (NIOSH IDLH = 5 ppm)
FDA: 50 ppb limit for medical devices

36. Ozone “Air Purifier” Ads
“thunderstorm in a box”
Greatly reduces pollutants such as:
MOLD MILDEW ODORS
BACTERIA FUMES DUST
POLLEN GASES CHEMICALS
SMOKE STALE AIR PET DANDER
FORMALDEHYDE SMOG GAS FUMES
“fresh as mountain air”
“provides relief from allergies & asthma”
“No harmful by products”

37. Shaughnessy and Weschler, (1999) “Growth of Submicron Particles as a Consequence of Ozone-Surface Reactions; Preliminary Data” Proceedings Indoor Air ‘99 Weschler, C.J. and Shields, H. C. (1999) “Indoor Ozone/Terpene Reactions As a Source of Indoor Particles”, Atmospheric Environment Nazaroff and Weschler (2004)“Cleaning Products & Air Fresheners: Exposure to Primary and Secondary Pollutants”, Atmospheric Environment Indoor Chemistry is Extremely Important…

38. Implications as to CADR
CADR tests conducted on air cleaners that produce ozone (intentionally or unintentionally) in the absence of a terpene source do not capture particle generation phenomena and thus overstate CADR in the presence of such a source

39. Alpine Industries reportedly has sold more than 3 million units since 1987 ($ billion retails sales) up until their litigation in 2001.
(LBNL – 58694, June 2005)

40. “…ozone is generally ineffective in controlling indoor air pollution.”
EPA, 1998:
“…ozone is generally ineffective in controlling indoor air pollution.”
“The public is advised to use proven methods of controlling
indoor air pollution.”

41. “Because of the documented negative health impact of ozone, especially for persons with asthma, and the lack of evidence for its ability, at low concentrations, to effectively ‘clean’ the air, the American Lung Association suggests that ozone generators not be used.” ALA ’97

42. Emerging Technologies
P.C.O.
UV-C
Sorbent technology
Ionization/electrostatic devices
Media filtration

43. Gas/vapor contaminants
Adsorption
Absorption
Catalytic oxidation/reduction
Botanical air cleaning (good luck)
Ozonation

44. Adsorption Chemisorption Nature of process Media Uses
e.g. activated alumina impregnated with potassium permanganate (HCHO oxidation)

45. Photocatalytic Oxidation (PCO)
Titanium dioxide (TiO2) is a semiconductor photocatalyst
UV light-driven catalytic oxidation of gas phase contaminants
Resultant oxidation of VOCs and degradation of bioaerosols

46. PCO Challenges reaction rate inhibition due to humidity
mass transport issues associated with high-flow rate systems
formation of products of incomplete oxidation (primarily aldehydes)
catalyst deactivation and inorganic contamination (dust and soil).

47. UVGI Irradiation
used in TB isolation rooms, waiting rooms, radiology areas
duct or upper room irradiation mounts
CDC (1994) considers only as supplemental to engineering controls (i.e. ventilation, HEPA, negative P)
not demonstrated to be highly effective against fungal spores

48. Application of UV upper room air irradiation ductwork/plenum
portable air cleaners

49. "Effectiveness of Germicidal Ultraviolet Irradiation for Reducing Fungal Contaminants within Air Handling Units"
Applied and Environmental Microbiology, Vol 67 #8, , August, 2001.
Levetin, E.,
Shaughnessy, R.J.,
Rogers,C.

50. Summary
Positive correlation between operation of UV-C lamps and reduction of microbial growth in duct lining and drain pan samples from ahu s
Effect on bacteria in water more pronounced than on fungi
No ozone buildup noted
Levetin, Shaughnessy, Rogers, 2001

51. Summary (cont’d)
UV-C is direct line-of-sight mechanism; areas not irradiated showed no visible improvement
Further studies needed as to overall effectiveness of UV-C in ahu s, and the effect on the passing air stream
Levetin, et al., 2001

52. “Effect of UVGI in HVAC on Workers’ Health” Menzies, et al, Lancet, Nov, 2003
Results:
Reduction of microbial/endotoxins on irradiated surfaces
Reduction in worker-related symptoms
Limitations:
Only 3 bldgs; nonrandomized intervention
Very low initial microbial concentrations
No effect on thermal/chemical indices
Only slight effect on worksite air microbes
No explanation for apparent health effects

53. “Effectiveness of UV in Ductwork”, A. R. T. I
“Effectiveness of UV in Ductwork”, A.R.T.I.,Van Osdell & Foarde, Nov 2003
Veg bacteria more susceptible while spore forming bacteria and fungi more resistant
Reliance on design eqns to predict kill may be prone to error; actual testing under environmental conditions recommended

54. Moisture control, properly designed dehumidifying/cooling HVAC processes, drain pans designed to drain, and installing nonporous surfaces downstream of coils should collectively continue to be primary approaches to controlling microbial growth in AHUs.

55. LBNL Report June 2005

56. Air Duct Cleaning Done well: air ducts are cleaned
Done poorly: occupants exposed to contaminants
Effect of cleaning on occupant exposure, not well defined
Low-bid often NOT the best bid
Routine use of biocides (sanitizers) is concern
EPA Report on duct cleaning