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Aaron Collins Profile picture
@masknerd
Jun 14 • 7 tweets • 2 min read Twitter logo Read on Twitter
[1]Far-UVC (222nm) efficiently inactivates microorganisms in the air and on surfaces and produces ozone in a single-bed-sized chamber
Waseem Hiwar, University of Leeds
#ICFUST2023
[2] This is a pre-recorded presentation. A mock room simulation looking at deactivating S. aurus and another pathogen(missed it) with 222nm. Collected aerosol using a Anderson 6 stage impactor and ozone monitored using 2B Tech(this is the right device to use!)[
[3] Missed irradiance level but think it was 4.0 mJ/cm^2. In this experience ACH in space was ramped from 1.5 to 9 eACH while lights were on. Reduction rates for different ACH was 95+%. Some impact to ACH on disinfection.
[4] Ozone measurements in the space showed strong correlation with ventilation ACH. 12 PPB to 51PPB increase in ozone from 1.5 ACH to 9 ACH.
[5] So higher ventilation reduces ozone, but has a slight impact on disinfection. Lower vent rates means virus floats in room longer, so to me this makes sense.
[6] @CathNoakes was asked if there was any additional to solution for atomization. This experiment just used water, but will explore bovine serum.
[7] My take is that IAQ will be the upper limit for power, and do we need 99.9% disinfection? Something to think about.

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More from @masknerd

Aaron Collins Profile picture
Jun 16
[1]Looking to the future of Far-UVC
Catherine Noakes, University of Leeds
@CathNoakes
#ICFUST
#ICFUST2023
[2]written in direct response to the conference (and during the conference) reminder: COVID has caused enormous caseload and death and pre COVID lower respiratory infection was already #4 cause of worldwide death.
[3] This is a huge health challenge worldwide
three vectors for air and infection: communicable diseases( TB measles, flu), opportunistic pathogens (aspergillusm, NTMs, etc), airborne role in other infections (mrsa, c diff, norovirus)
Read 22 tweets
Aaron Collins Profile picture
Jun 16
[1]How it goes forward: A blueprint for communication
with the public about GUV
Kathleen McPhaul, University of Maryland
#ICFUST
#ICFUST2023
[2] (First shout to Balvi for the support on this one! (

Going to address health literacy. The context is the extreme importance of getting the messaging right and letting this space make the change it can
[3] Examples of health messaging that went off track from a public health messaging perspective:
mask effectiveness: they work, they worked, that message was missed. Vaccinations work, but the term "break through" diminished (as opposed to "saving lives, decreasing illness, etc"
Read 24 tweets
Aaron Collins Profile picture
Jun 16
[1] Roundtable discussion with participants from both governmental and non-governmental agencies on future regulatory pathways for Far-UVC
#ICFUST
#ICFUST2023
[2] Moderator: Lew Radonovich (CDC, NIST)
Participants: Belal Abboushi (Pacific Northwest National Laboratory), Aline Heffernan (EPA Office of Pesticide Programs), Cameron Miller (NIST), David Sliney (perspectives from ACGIH), Richard Vincent (perspectives from ASHRAE)
[3] Lew Radonovich (CDC) opens that we will discuss the regulatory space(or really lack of)
NIOSH in US is focused on occupational safety and health, seek knowledge and apply it to the workplace. Will move through the panel now.
Read 25 tweets
Aaron Collins Profile picture
Jun 16
[1] Germicidal Ultraviolet Light dosing
recommendations from the field
PJ Piper, Far UV Technologies
[2] Overview of Upper-Room vs Whole Room(222 nm). Aside: Airplanes hard, need $300M insurance policy so not happening any time soon.
[3] Club Cafe - Boston, MA example install.
Floorplan important, and ceiling heights important.
Originally discussed with clients log kill rate, but will transition to eACH how adjacent industry talk
Read 7 tweets
Aaron Collins Profile picture
Jun 16
[1] Goniophotometric intensity and spectral measurements in the UV for a Care222 Excimer lamp unit with and without a filter and diffuser unit
Rolf S. Bergman, Rolf Bergman Consulting
[2] We care about total photonic output for disinfection. Wanted to explore spectrum impacts off axis, and what happens with difuser.
Lamps: USHIO B1 with and with out filter, and also with added diffuser
[3] Data shows angular difference with and without filters in terms of 222nm output(as expected). Spectral data with off-axis shows reduction in output as well(expected) and the filter reduced light above 235nm which is good.
Read 5 tweets
Aaron Collins Profile picture
Jun 16
[1] Accurate germicidal efficacy and photobiological hazard measurement of far-UVC sources.
Mike Clark, Gigahertz Optik GmbH
#ICFUST2023
#ICFUST
[2] Need better meters especially between fluence and irradiance. UV radiomerters - widely used, convenient
UVspectroradiometers - much more comprehensive
[3] Radiometers often calibrated for near radiation. Most commercial radiometers don't cover the range of Far UV-C. Also need to match spectral response to wavelength of interest or big errors. Knowledge of light source used in calibration is very important!
Read 8 tweets

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