January 18, 2024
EPA/600/S-24/148
Cleaner Indoor Air During Wildfires Challenge - Phase 2
Evaluation Summary
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Disclaimer: The views expressed in this short report are those of the authors and do not necessarily represent the views
or policies of the U.S. Environmental Protection Agency. Any mention of trade names, products, or services does not
imply an endorsement by the U.S. Government or the U.S. Environmental Protection Agency. The EPA does not endorse
any commercial products, services, or enterprises.
Background
Wildfire smoke and poor ambient air quality around the world contribute to substantial clinical, public health, and economic societal
burdens. Current public health advice for protection from smoke exposure during wildfires is to stay indoors, preferably in a "cleaner
room" with filtered air, close windows and doors, and minimize physical exertion. Owning and maintaining air cleaners currently on
the market is unaffordable and/or unattainable for many people who are most at risk of experiencing health effects from exposure to
wildfire smoke. In addition, wildfires often occur in the summer and early fall in regions of the U.S. where many homes do not have
air conditioning, so closing windows can lead to very high indoor temperatures and related health effects. Through the Cleaner Indoor
Air Daring Wildfires Challenge, the Environmental Protection Agency (EPA) and its partners intended to encourage the development
of new approaches or technologies that met the following objectives:
Remove fine particles (PM2.5) during smoke and high air pollution episodes;
Are low-cost to purchase, operate, and maintain (including filters or any other consumables);
Are easy to use, not too noisy, and meet safety requirements; and
Include additional desirable criteria such as cooling a room without drawing in smoky air; adding a battery or other option for
operation during power outages; and/or reducing other air pollutants, such as volatile organic compounds (VOCs).
EPA partnered with ten other federal, state, local, and tribal agencies on this Challenge including: U.S. Department of State; Centers
for Disease Control and Prevention's National Center for Environmental Health and National Institute for Occupational Safety and
Health; National Institute of Standards and Technology; California Air Resources Board; Oregon Health Authority; Missoula City-
County Health Department; Puget Sound Clean Air Agency; Lane Regional Air Protection Agency; and the Hoopa Valley Tribal
EPA. The primary intent of the Challenge was to focus attention on the problem, inspire development of innovative solutions, and
stimulate the market to commercialize effective solutions.
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January 18, 2024
The Challenge was offered in two phases:
Phase 1, launched and completed in 2021, was a theoretical, or design, challenge requiring an in-depth written proposal but not
requiring development of a prototype. Five Phase 1 winners and three Honorable Mention (non-monetary) honorees were
selected for awards.
Phase 2, launched in July 2022, invited the Phase 1 winners and Honorable Mention awardees to submit prototypes of their
technologies for evaluation.
The Cleaner Indoor During Wildfires Challenge is one component of a broader research project entitled the Wildfire Advancing
Science Partnerships for Indoor Reductions of Smoke Exposures (ASPIRE) Study. Learn more about the Wildfire ASPIRE Study at:
https://www.epa.gov/air-research/wf-aspire.
Evaluation Process
Prototypes progressed through a series of qualitative and quantitative tests as outlined in the Cleaner Indoor Air During Wildfires
Challenge: Phase 2 Vision, Criteria, and Prototype Submission and Evaluation Plan and Cleaner Indoor Air Challenge: Prototype
Evaluations - Quality Assurance Project Plan (QAPP) shared with Solvers through the Challenge contractor, Wazoku. There were a
few changes to the evaluation testing outlined in the QAPP, specifically:
The PM size distribution was not measured during the tests.
Black carbon was not measured during the tests.
Temperatures were measured on the external surfaces of the air cleaner and next to the control switch/button only.
Air output flow and temperature were measured inside the laboratory with a climate-controlled environment. The fan output
temperature was compared to the background room temperature.
Prototypes were first evaluated for potential electrical, mechanical, and/or chemical hazards. If one or more safety hazards was
observed or if any hazard was anticipated to occur when the prototype was operated through a smoke event lasting up to 14 days, the
prototype was disqualified, and no further testing was conducted.
Some portable air cleaners generate ozone, which may be harmful to health. Therefore, the prototypes that passed the safety
evaluations were then operated for up to 8 hours in a controlled-environment chamber to assess if the prototype produced ozone. If a
prototype generated ozone at or above 50 parts per billion (ppb), the prototype was disqualified, and no further testing was conducted.
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January 18, 2024
If, after these evaluations, the prototypes were not disqualified, a series of tests to assess the 'must have' and 'desirable' Challenge
criteria were conducted.
Criteria
Tested
Description
Target
PM
2.5
reduction
3
Reductions in PM25 concentrations starting at ~ 150 ng/m
3
Time to reach 80% reductions (30 ng/m ); testing
will stop at steady state conditions or 1 hour,
whichever is reached first
Must
Have
Criteria
Costs
Expected consumer cost
<$100 USD
Noise
Measure noise levels during operation
<55 dBA
Ease of use
Assess operator effort to set-up, operate, and maintain
Consider number of steps to set up and
maintenance and power requirements
Evaluate size for residential use
1 1
1 1
Cooling
1 1
Evaluate airflow and temperature
1 1
Increased output airflow and/or decreased
temperature
Operating
costs
Evaluate annual estimated costs, availability of replacement
parts, and generated waste
Low annual costs to operate and maintain, easy
access to replacement parts, minimal waste
Desirable
Criteria
Alternative
power
source
Estimate run time and performance using alternative power
source
Higher points if alternative power source is included
in initial cost and supports longer run times
Reduction
of other
pollutants
Measurement of VOCs and/or other pollutants
VOC reductions (%) during same timeframe as
reaching 80% PM25 reductions
I I
i I
E valuator's
judgment
1 ' 1
Characteristics not captured in other judging elements, but relevant to Challenge goals
As outlined in the Cleaner Indoor Air During Wildfires Challenge: Phase 2 Vision, Criteria, and Prototype Submission and
Evaluation Plan, a short-form report summarizing the prototype test results and qualitative feedback would be provided to each
Solver. The results of the testing are summarized below for the following prototype:
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January 18, 2024
Prototype #5 - AeroScrubber
Point of Contact - Eric Nutsch, BOTE Innovations LLC, Eric@BOTE.LLC
Description: The tear-dropped shaped prototype uses ultrasonic agitation to generate an aerosol of water droplets that mixes with
incoming air in a holding chamber and then collects particle-laden droplets on a filter. Particulate matter (PM) and total hydrocarbon
removal were evaluated using utility power and battery power.
Evaluation - Disqualification Conditions:
Parameter
Value or Summary
Safety Evaluation
Passed
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January 18, 2024
Parameter
Value or Summary
(Electrical mechanical
chemical)
Minor safety issues were identified including: the use of unlisted components, the potential for water leakage
into the battery compartment, and external water leakage.
Not all live parts were insulated.
The float circuit to prevent operation when the water level is too low and did not work when tested. The
voltage regulator was not secured in the battery compartment.
Touchpoint
temperature
(maximum, average over
10 minutes)
70° F
Ozone Evaluation
(Average chamber O3
concentrations 1
hour period)
a.
Ql
0.3
0.2
0.1
0
s 1
-0.2
-0.3
-0.4
5:00 PM
y/ Passed
No ozone generation was observed.
03 [ppb]
7:00 PM
9:00 PM
11:00 PM
1:00 AM
Evaluation - 'Must Have' Criteria:
Parameter
Value or Summary
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January 18, 2024
Parameter
Value or Summary
PM2.5 Reduction
(NormalizedPMconcentrations for 60 minutes or average time until 80% ofPMwas removed)
- Laboratory Evaluation
Battery Powered:
Valid Pest: Pest-2 {battery issues resulted in only one valid test)
Initial PM2.5: 197 jug/m3
Average 80% PM2.5 removal threshold: 40 jug/m3
Did not remove PM.
Normalized PM Removal
1-8 ,
0.2
Power Supply:
10 20 30 40 50
Elapsed Time (min)
60
- Test-1
- Test-2
- Test-3
- Test-4
. Natural Decay
80% Removal Threshold
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January 18, 2024
Parameter
Value or Summary
Valid Tests: Test-1, Test-2, Test-3
Average initial PM2.5: 201 jug/m3
Average 80% PM2.5 removal threshold: 40 jug/m3
Did not remove PM.
Normalized PM Removal
1.6
1.4
1.2
ns
'-P
0.S
cl 0.6
0.4
0.2
¦ Test-1
¦ Test -2
¦ Test -3
¦ Natural Decay
S094 Removal Threshold
0 10 20 30 40 50 60 70
Elapsed Time (miri)
Clean Air Delivery Rate
(CADR)
Battery Power: Not Applicable - No PM removed
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January 18, 2024
Parameter
Value or Summary
(Average CFM)
Power Source: Not Applicable - No PM removed
- Power Draw
(Average W)
23 W
Noise Evaluation
(1.5 m from fan outlet,
averaged over >_10 minutes)
53.2 dB
Consumer Costs
(Information submitted by
Solver)
Total per unit cost at 10,000 volume: $71.06
Estimated retail price: $100.00
Cost per unit of clean air
delivered
Batterv Power:
Not Applicable - No PM removed
Power Source:
Not Applicable - No PM removed
Ease of Use
(Independent evaluation of usability)
- General
The prototype and its instructions for wall-powered operation were easy to understand. The ease of use of the
battery powered configuration was not evaluated. The primary concerns were related to possible water leaks during
operation.
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January 18, 2024
Parameter
Value or Summary
Likert
Scale
Set-up
Moderate
The written instructions lacked clarity regarding the precise location for adding soap and citric acid
and it was challenging to locate the maximum water fill line.
It took approximately 7 minutes to fill the prototype with water, soap, and citric acid.
The instructional video provided by the Solver was helpful to ensure proper set up of the prototype.
Operation
Easy
The prototype is designed with one switch and a single power setting - so very easy to operate.
Maintenance
Moderate
The fuse is placed in the battery compartment which requires tools to access.
Determining when the front air filter requires handwashing vs. replacement was difficult.
Both prototypes experienced a minor issue with water leakage.
Evaluation - Additional 'Desirable' Criteria:
Parameter
Value or Summary
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January 18, 2024
Parameter
Value or Summary
Cooling
(Air cleaner outlet temperature and velocity - averaged values measured 24 "from outlet of air cleaner)
Airflow temperature
(° F, 0.5 m from outlet)
The air cleaner outlet temperature was approximately the same as room air.
Temperature 0.5 m from Air Cleaner Outlet
High Speed
68.9
68.8
68.7
U-
0
68.6
V
3
68.5
L.
68.4
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*>
68.3
i-
68.2
68.1
68
+4"
center
12"
7.5-
Air velocity
(feet/min [fpm], 0.5 m
from outlet)
The air cleaner outlet air velocity was equivalent to a gentle breeze at the center.
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January 18, 2024
Parameter
Value or Summary
400
E 300
o.
200
O
£ 100
0
Air velocity at 0.5 m from outlet
High Speed
12"
7.5"
+4"
center
-4"
Annual Operating and
Maintenance Costs
(information submitted by
Solver)
Maintenance costs:
Filter replacement (every 2 years): $15
Operating costs (24 hr/dav):
1 Month: $3.09; 3 Months: $9.26; Annual: $37.04 per year
Alternative Power Source
Multiple power options include an onboard battery that can be charged when not running and a car accessary port.
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January 18, 2024
Parameter
Value or Summary
VOC Reduction
(Normalized total
hydrocarbon (THC)
removal)
Batten- Power:
No VOC removal was observed.
1.05
0.7
Power Supply:
Normalized Total Hydrocarbon (THC) Removal
-Test-l
¦ Test-2
-Test-3
¦ Test-4
-Natural Decay1
10 20 30 40 50 60 70
Elapsed Time (min)
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January 18, 2024
Parameter
Value or Summary
No VOC removal was observed.
1.2 .
1
Normalized Total Hydrocarbon (THC) Removal
0.8
~ra
£
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CJ
-p 0.6
Test -1
1
U
X
1
0.4
0.2
n
--Test -2
-~-Test-3
Natural Decay
0 10 20 30 40 50 60 70
Elapsed Time (min)
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January 18, 2024
Feedback from EPA Review and Judging Process
EPA summarized the results of the evaluations and shared this information with a Judging Panel. The Phase 2 Judging Panel included a range of
expertise including indoor air quality experts, product engineers, and others with public health and/or communications/risk expertise from Federal,
state, and local agencies, as well as academia and the private sector. Input from the Judging Panel was discussed with our Challenge Partners and
additional feedback was provided by these Partners. Collectively, the recommendations from the Judging Panel and the Challenge Partners
informed EPA's decisions to select the Phase 2 Challenge winners.
No one Solution met all Challenge criteria. Partial awards were selected to recognize two Solutions that represented novel, innovative ideas and fit
different niches for residential air cleaner needs during wildfire smoke events. These awards do not include EPA endorsement of the final products
as further development is needed for both Solutions chosen as the Phase 2 winners.
Feedback on each prototype was categorized to recognize specific strengths of the design and opportunities to improve/further develop the design.
Strengths
o The prototype met many of the Challenge criteria (however, it did not meet the primary criteria, PM2 5 reduction).
¦ When operating, the prototype was quiet.
¦ The cost analysis provided by the Solver met the Challenge target.
o The prototype was designed to be heavier at the bottom, reducing any potential tipping hazards.
Opportunities for Improvement/Further Development
o The prototype failed to meet the primary Challenge criterion, PM2 5 reduction.
o Testing indicated that the design led to a net increase of measured PM2 5 in the room, likely due to its water aerosolization approach.
o The instructions did not differentiate water type but did say to add dish soap as well as citric acid to protect against mold growth. The EPA
evaluation team followed the instructions and still saw mold. Specifying the use of distilled water may be appropriate since tap water
contains salts.
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