Title: Ultraviolet Germicidal Irradiation for Reducing Disease Transmission and Energy Use
1Ultraviolet Germicidal Irradiation for Reducing
Disease Transmission and Energy Use
- Shelly L . Miller
- Associate Professor, Mechanical Engineering
Environmental Engineering ProgramUniversity of
Colorado, Boulder
2Objectives
- Since 1997, our research group has studied the
efficacy of ultraviolet germicidal irradiation
(UVGI) for inactivating airborne bacteria,
viruses, and fungal spores - Investigated temperature, relative humidity, and
photoreactivation affects, as well as UV
radiation distribution, air mixing, and lamp type - Funded by CDC, NIOSH, Gilbert Foundation, NSF,
and Industry partners - Experimental paradigms include
- Multi-pass
- Intrinsic
- Upper-room air
- UV-HEPA air cleaners
- Single-pass
- In-duct
- Small-scale personal devices
- CFD Modeling
3UVGI as an Engineering Control
- The use of ultraviolet germicidal irradiation
(UVGI) for the sterilization of microorganisms
has been studied since the 1930s, mostly surface
and water effects - Microbes are uniquely vulnerable to radiation at
wavelengths at or near 260 nm due to the
resonance of this wavelength with molecular
structures - This wavelength is not naturally observed at
the earths surface it is absorbed in the
stratosphere by ozone
4UVGI Lamps
- mercury vapor lamps are most commonly used in
applications, providing 254 nm radiation - Mercury toxicity is a concern in some
applications - Non-toxic sources are not yet commercially
available - We are assessing prototype diodes and xenon lamps
- Xenon produces peak radiation at 242 nm
5UV Irradiation and DNA
Formation of dimers between adjacent thymine
nucleotides promotes cellular inactivation
6Guidelines for Preventing the Transmission of M.
tuberculosis in Health-Care Settings
- Environmental controls are the second line of
defense in the TB infection control program,
after administrative controls - Environmental controls include technologies for
the removal or inactivation of airborne M.
tuberculosis - These technologies include local exhaust
ventilation, general ventilation, HEPA
filtration, and UVGI - (MMWR December 30, 2005 / 54(RR17)1-141)
7Multi-pass
- IntrinsicUpper-room air
- UV-HEPA air cleaners
8Building applications
- Crowded environments where unsuspected infectious
persons may be present (e.g. jails, homeless
shelters, hospital waiting rooms) - Rooms in which infectious aerosol may be
generated (e.g. hospital treatment and isolation
rooms, rooms in a home, indoor pool facilities)
and additional control is needed - Rooms in which HVAC retrofits are difficult to do
but additional air changes are needed to reduce
risk of infections (e.g. hospital treatment and
isolation rooms) -
9Measles in Schools
- Wall-mounted UV lamps installed in three NY
schools showed no difference in measles
incidence, but the UV lamps did modify the
spread of the disease in the school with the
most lamps, the outbreak occurred over 4 months,
compared to over 1 month in the school with no
lamps - (Perkins et al., 1947)
10(No Transcript)
11CU Larson Laboratory
- T and RH control
- 87 m3
- Full-scale computer controlled HVAC system
provides ventilation air, both outdoor and
recirc, at 2-8 ACH
12Z Value
- First order reaction rate coefficient IRUV
(sec-1) normalized by average UV fluence rate (?W
cm-2) -
- Z-value is directly proportional to UVGI
inactivation rate - a higher Z-value indicates a lower resistance of
the microorganism to inactivation by UV radiation
and vice versa - Adopted from medical community (Riley et al.
1976 Riley, 1988, Riley and Nardell 1989)
13Z value for Aspergillus versicolor is order of
magnitude smaller than the Z value for M.
parafortuitum
14The upper-room air inactivation rate provided by
our 5 fixture 216 W system for A. versicolor is
0.4 h-1 (Kujundzic et al., 2005) compared to 16
h-1 for M. parafortuitum
15Photoreactivation may be an important factor95
RH, 25 C, 0 ACH ventilation Effects observed
in intrinsic configuration, but not at full-scale
M. parafortuitum
no sunlight
sunlight
- (Peccia and Hernandez 2001) (Xu et al., 2005)
Light-activated enzymatic repair of thymine
dimers may decrease airborne UV-induced
inactivation rate (Gillis, 1972)
16Increasing UV fluence rate does not increase
inactivation rate linearly (Xu et al., 2005)
Z value for M. para
17M. parafortuitum
Inactivation Rate (1/h)
Increasing RH from 50 to 90 decreased the
inactivation rate by half (Xu et al., 2005)
18M. parafortuitum
Inactivation Rate (1/h)
Unevenly distributed UV radiation results in 30
lower inactivation rates (Xu et al., 2005)
19Effectiveness (E)
- Quantifies improvement in indoor air quality that
is associated with the technologys use
E ranges between 0 and 1E 1 ideal
performanceE 0 complete lack of improvement
20Effectiveness
M. bovis BCG
M. parafortuitum
B. subtilis
- UVGI reduces culturable concentrations by 40-95
- Effectiveness depends on microorganism (Xu et
al., 2003)
21M. parafortuitum
At 6 ACH and wintertime ventilation conditions
UVGI effectiveness decreased from 89 to 12
when the mixing fans were off(Xu et al.,
2005).
22HEPA-UV Air Cleaners In an Indoor Therapy Pool
Building
(Kujundzic et al. 2005)
Pool Air (1,100 m3)
Outside Air
Pool Water (208 m3) Residence Time 6 h T33oC
12 UV Units
6 Sand Filters
Addition of H2O2
23Culturable Bacteria
(Kujundzic et al., 2005)
69 (Y1) and 80 (Y2) REDUCTION
24Single-pass
- In-ductSmall-scale personal devices
25Building applications
- Irradiation of cooling coils an drip pans
- Limited scientific studies to assess impact of
this application - Anecdotally it seems to work well
- Two scientific studies recently completed showed
no effect - Irradiation of recirculation air within HVAC
system
26HVAC Guinea Pig Study
- Guinea pigs exposed simultaneously in 2 separate
chambers, one receiving unchanged air from a TB
ward, and the other, ward air that was irradiated
with UV-C. A total of 63 guinea pigs contracted
TB over a 2-year period, and all were breathing
unirradiated air from ward - (Riley et al. 1962)
27Residential Asthma
- Study of 19 asthmatic children in homes with
central AC systems in which UV lamps were
installed showed a statistical improvement in
PEFR variability in subjects with UV lamps
compared to no UV lamps - (Bernstein et al. 2006)
28Impact of in-duct UV on office workers
- Double-blind cross over study of 771 participants
- 3 office sealed air-conditioned buildings
- UV was alternately off for 12 weeks, on for 4
weeks, and repeated 3 times - Operation of UVGI reduced surface microbial
contamination by 99 - Use of UVGI was associated with significantly
fewer work-related symptoms overall, as well as
respiratory and mucosal symptoms than was non-use - (Menzies et al. 2003)
29Impact of in-duct UV on office workers
30In-Duct UVGI
- Bacteria continuously aerosolized outside near
HVAC supply intake - High wattage UVGI in recirculation duct
- Sample upstream, downstream
- Single-pass efficiency determined by comparing
upstream and downstream concentrations
31In-Duct UVGI Single Pass Efficiency
91
80
75
Duct velocity 2.2 m/s No inactivation at
velocity of 5.1 m/s(kujundzic et al., 2006)
32Small-Scale Personal Device
- Requirements
- High flow rate
- Non-toxic UVGI source
- Coated to enhance reflectance
33UV Source
- LEDs
- solid state, expensive, low UV efficiency
(0.3), 45-65 mW UV array - Mercury
- Cheap, efficient (10), toxic, peak at 254 nm, 1
W bulb - Xenon
- Not commercially avail, efficient (10),
nontoxic, peak at 270 nm, prototype built for
project
UV fluence rate predictionin tube with coating
UV spectrum for Xenon lamp
34CU Experimental Test Facility
UV Radiation Exposure tube
UV source
Sampling upstream and downstream of UV tube
Equilibration chamber and aerosolization system
35B. Subtilis Hg uncoated tube
Coating enhanced inactivation by 25-28
36Energy Implications
- Mostly anecdotal evidence
- One MS thesis presents economic analysis
- More research needed
37Anecdotal Evidence
- Tacoma Jail
- Installed UV lights in HVAC VAV box/cooling
coils, went from 100 outside air to 70 OA and
30 recirc - Saved 34,100 therms of natural gas/yr
- Review of utility bill confirms they saved gt
70,000/yr in natural gas, overall saved 55,000
after accounting for parts/labor
38Anecdotal Evidence
- Florida Hospital
- Installed UV lights in one 6000 cfm unit, near
cooling coils where visible mold and clogging of
coil apparent - Within weeks of installation, static pressure
over coil decreased from 1.8 in wg to 0.7 in wg - Air velocity doubled from 230 fpm to 520 pfm
- 4900 in savings - 2000 installation cost
2900 - Also observed less mold build up in duct work,
reducing maintenance costs
39Anecdotal Evidence
- Boston Museum of Fine Arts
- Noticed a mold problem in humidifiers
- Had to drain and clean humidifiered almost daily
- Installed UVGI devices above humidifier sump and
downstream of chilled water coils - Standing water much clearer, huge reduction in
maintenance and cleaning procedures - American Electric Power, Dallas
- Installed UVGI in air handlers
- Eliminated cleaning programs
- Saw significant drop in pressure across coil,
translating into energy savings of 139,000 over
two-yr period
40Dreiling 2008, An Evaluation of UVGI Technology
in Health Care Facilities
- Compared three systems to a baseline 3900 cfm
HVAC system - Upper-room UVGI system
- HVAC system with increased ACH
- UVGI system in an AHU
41Dreiling 2008, Economic Evaluation Summary
- Upper-room UVGI
- increased predicted time for 99 disinfection
from 46 minutes to 18 minutes - Increased ACH to 15.2 from 6 ACH
- 62 increase in total cost
- HVAC system with increased ACH
- Similar to upper room UVGI, in both cost and
increased ACH - UVGI in AHU
- Room still at 6 ACH
- Cooling coils cleaned
- More focused on the fan energy consumption
42Acknowledgements
- CDC, NIOSH, NSF, Gilbert Foundation, Industry
Sponsors - Students at CU Elmira Kujundzic ,Fatimah
Matalkah, Cody Howard, Jordan Peccia, Peng Xu - Colleagues Mark Hernandez, Millie Shafer, Kevin
Fennelly, Byron Jones, DTU faculty, - Joint Center for Energy Management
43References
- Dreiling J. (2008). An Evaluation Of Ultraviolet
Germicidal Irradiation (UVGI) Technology In
Health Care Facilities, MS Thesis, Kansas State
University. - Bernstein JA. (2006). Health effects of
ultraviolet irradiation in asthmatic childrens
homes, J Asthma 43255-262. - Jamriska M et al. (2000). Effect of ventilation
and Filtration on Submicrometer Particles in an
Indoor Environment Indoor Air 10(1)19-26 - Kujundzic E et al. (2007). Ultraviolet germicidal
irradiation inactivation of airborne fungal
spores and bacteria in upper-room air and in-duct
configurations, JEES 61-9. - Kujundzic E et al. (2006). Air cleaners and
upper-room air UV germicidal irradiation for
controlling airborne bacteria and fungal spores,
JOEH 3536-546. - Kujundzic E et al. (2005). Effects of
ceiling-mounted HEPA-UV air filters on airborne
bacteria concentrations in an indoor therapy pool
building, JAWM 55210-218. - Mendell MJ et al. (2002). Indoor particles and
symptoms among office workers results from a
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13296-304. - Menzies D et al. (2003). Effect of ultraviolet
germicidal lights installed in office ventilation
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double-blind multiple cross-over trial, The
Lancet 3621785-1791. - Perkins et al. (1947). Effect of ultra-violet
irradiation of classrooms on spread of measles in
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73529-537. - Riley et al. (1962). Infectiousness of air from a
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