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jljcolorado's profile
Prof. Jose-Luis Jimenez
Prof. Jose-Luis Jimenez
Prof. Jose-Luis Jimenez
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@jljcolorado

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Prof. Jose-Luis JimenezVerified account

@jljcolorado

Dist. Prof. Chem. & CIRES, Univ. Colorado. #HighlyCited2021, Fellow AAAR & AGU. Aerosols, pollution #EndFossilFuels #COVIDisAirborne http://Bit.ly/FAQ-A  http://Bit.ly/c-est 

Boulder, CO
colorado.edu/chemistry/jose…
Joined July 2009

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    1. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

      1/ Air cleaners: the good, the dubious, and the ugly With pandemic & major contribution of aerosol spread, many ppl wanting “air cleaning devices” to reduce / remove virus. Unfortunately many types, aggressive & misleading marketing of unproven & potentially dangerous cleaners

      36 replies 320 retweets 693 likes
      Show this thread
    2. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

      Prof. Jose-Luis Jimenez Retweeted Linsey Marr

      2/ Critical background: virus is NOT "naked" (0.1 um) in the air. Aerosolization processes in respiratory system produce larger particles, likely mostly 1-10 um (https://twitter.com/linseymarr/status/1290617594597310465 …). Unfortunately "0.1 um virus naked in the air" is frequently repeated misconception.

      Prof. Jose-Luis Jimenez added,

      Linsey MarrVerified account @linseymarr
      Here's the presentation @kprather88 and I sent to Fauci about aerosols: https://drive.google.com/file/d/1T4Rb-HFbWp4DOua--uBmMhhRqf9JNQfT/view?usp=sharing … https://twitter.com/kprather88/status/1290477157970370561 …
      5 replies 35 retweets 165 likes
      Show this thread
    3. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

      3/ Best air cleaning: filters; work, no side effects (a) Filters on building / home HVAC, furnace or AC, MERV13 if possible (https://www.ashrae.org/technical-resources/filtration-disinfection …) (b) Portable HEPA filter, great, but expensive (https://shellym80304.com/2020/06/15/a-hopefully-helpful-short-report-on-air-cleaners/ …) (c) Cheap fan-filter, $40! (https://www.wired.com/story/could-a-janky-jury-rigged-air-purifier-help-fight-covid-19/ …)

      6 replies 69 retweets 230 likes
      Show this thread
    4. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

      Prof. Jose-Luis Jimenez Retweeted Shelly Miller, PhD

      4/ For selecting HEPA cleaners, see the link above, also CU-Harvard spreadsheet: https://twitter.com/ShellyMBoulder/status/1291071670313050112 …. Also AHAM certification in US https://ahamverifide.org/ , CARB certif. https://ww2.arb.ca.gov/our-work/programs/air-cleaners-ozone-products/air-cleaner-information-consumers …, en Espana: https://www.eurovent-certification.com/es/technical-insight/air-purification-device … (But ONLY HEPA, not other types even if cert.!

      Prof. Jose-Luis Jimenez added,

      Shelly Miller, PhD @ShellyMBoulder
      Replying to @LMCR_10 @CathNoakes and 5 others
      we are recommending supplement with air cleaners https://docs.google.com/spreadsheets/d/1NEhk1IEdbEi_b3wa6gI_zNs8uBJjlSS-86d4b7bW098/edit#gid=1882881703 …
      4 replies 34 retweets 116 likes
      Show this thread
    5. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

      5/ Many manufacturers of other air cleaners dismiss HEPA air cleaners as ineffective. Excuse my French… but this is BS! Eg this huge error, actually in a paper in press! (https://www.sciencedirect.com/science/article/pii/S0196655319309836?via%3Dihub …). Know 1 of authors, is trying to get this corrected as he had not noticed beforepic.twitter.com/OIoZLjrRQY

      3 replies 24 retweets 88 likes
      Show this thread
    6. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

      6/ HEPA = 99.97% filtering efficiency at 0.3 um, better at any other size. See: https://www.epa.gov/indoor-air-quality-iaq/what-hepa-filter-1 … (But this causes pressure drop, not usable in some pre-existing systems, then go MERV13 if possible)

      2 replies 24 retweets 106 likes
      Show this thread
      Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

      7/ Selecting HEPA cleaner, DO NOT want ones that also have UV, ions or other bells-and-whistles. More $, don’t help, can be dangerous (see below). Filter already capturing the virus, which will decay there. Just change filter carefully, put in sealed bag, wash hands

      8:38 AM - 7 Aug 2020
      • 41 Retweets
      • 140 Likes
      • Kreus cathryn farnsworth Amanda says Covid is airborne. Upgrade your mask! Pepper MW LeaLoo 😷🪟 Theo akosispartacus Thad Crocker Nicola Makin #FBPE 💙🕷😷🦆🇪🇺🇦🇬🇩🇪🇬🇧🇮🇪🛩
      4 replies 41 retweets 140 likes
        1. New conversation
        2. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          8/ There could be some infective virus left on filter when changing it, but hard to get it back to the air. Change outdoors, with mask, just to be extra careful.

          2 replies 17 retweets 94 likes
          Show this thread
        3. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          9/ Germicidal UV: this method is known to work very well to destroy viruses including SARS-CoV-2 (e.g. https://www.dhs.gov/science-and-technology/sars-airborne-calculator …). - But expensive, need maintenance, very dangerous if installed improperly. Experts only recommend when nothing else possible: https://www.sciencedirect.com/science/article/pii/S0160412020317876 …

          8 replies 24 retweets 108 likes
          Show this thread
        4. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          10/ For UV (& other types below), **very important** to make sure that they do NOT produce ozone, which is very damaging to lungs (https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=149923 …). Ozone generators only seem to be a problem in the US, and not Europe or elsewhere (HT Bart Croes).

          6 replies 24 retweets 113 likes
          Show this thread
        5. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          11/ See CARB list of devices to avoid: https://ww2.arb.ca.gov/ozone-generating-consumer-products … If cleaner does NOT certify that it does NOT make ozone, DO NOT BUY!

          2 replies 21 retweets 102 likes
          Show this thread
        6. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          12/ Other types of air cleaners: ions, oxidation, plasmas etc. Cause some air chemistry. Probably effective at removing or deactivating the virus. But same chemistry that deactivates the virus by oxidation of its organic molecules, can also produce toxic compounds

          5 replies 18 retweets 84 likes
          Show this thread
        7. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          13/ Toxics formed from from oxidation of volatile organic compounds (VOCs). VOCs are very abundant in indoor air, much more than outdoor air (https://pubs.acs.org/doi/abs/10.1021/acs.est.9b04689# …).

          1 reply 15 retweets 70 likes
          Show this thread
        8. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          14/ Manufacturers often brag their products reduce VOCs. Problem is that do not convert them to CO2 and H2O, impossible in small devices. Studied this chemistry in gory detail, applies to air cleaners (e.g. cover article in Chemical Society Reviews, https://doi.org/10.1039/C9CS00766K …).

          3 replies 12 retweets 66 likes
          Show this thread
        9. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          15/ See paper from MIT (http://krollgroup.mit.edu/papers/isaacmanVanwertz_2018.pdf …). Initial VOC (a-pinene, eg cleaners, fragrances etc, often abundant indoors) destroyed quickly. But... MANY products, more oxidized. Same in air cleaners, same oxidation that hurts the virus oxidizes VOCs.pic.twitter.com/CUWeUJ040p

          1 reply 13 retweets 60 likes
          Show this thread
        10. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          16/ Products of VOC oxidation include formaldehyde, product of oxid. of almost all VOCs, quite toxic (http://www.euro.who.int/__data/assets/pdf_file/0014/123062/AQG2ndEd_5_8Formaldehyde.pdf …). eg FEMA trailers after Katrina, form. from wood glue was very dangerous. Other potential toxics: peroxides, aldehydes, nitro-compounds, etc

          2 replies 13 retweets 71 likes
          Show this thread
        11. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          17/ These byproducts are not seen on the studies that the manufacturers have provided. This is because they require more advanced VOC measurements, such as chemical ionization mass spectrometers (https://www.aerodyne.com/product/chemical-ionization-time-flight-mass-spectrometer-tof-cims/ … or https://www.ionicon.com/series/details/ptr-ms-trace-voc-analyzers …).

          1 reply 13 retweets 56 likes
          Show this thread
        12. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          18/ Studies can be done, many research groups have instruments. Pls reply if you know of any such study, manufacturers have not provided any upon request. Because TMK this has not been studied, we don’t know how dangerous it is.

          3 replies 10 retweets 51 likes
          Show this thread
        13. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          19/ But we should follow **precautionary principle** (https://en.wikipedia.org/wiki/Precautionary_principle …), especially since very effective and completely safe filtering-based solutions exists.

          2 replies 12 retweets 57 likes
          Show this thread
        14. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          20/ Back to germicidal UV, can photolyze O3 present indoors, although at low concentrations --> similar chemistry (see our paper https://doi.org/10.1039/C9CS00766K …). This is an additional reason to avoid UV, unless really really really the HEPA filters etc. cannot be done.

          1 reply 11 retweets 54 likes
          Show this thread
        15. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          21/ BOTTOM LINE: YES: better filters in HVAC, portable HEPA cleaners, and makeshift fan-filter cleaners If above just not enough (e.g. some hospitals) and professionals available to install properly AND maintain: germicidal UV Avoid: ions, oxidation, plasmas, and UV within HEPA

          3 replies 33 retweets 120 likes
          Show this thread
        16. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          22/ Comments? - Happy to update this, if peer-reviewed evidence addressing all oxidation products is provided. Not seen any so far. - Expect dismissal from manufacturers (again). But please provide evidence. - Comments? Anything I missed? @ShellyMBoulder @CorsIAQ @IAQinGWN

          14 replies 8 retweets 55 likes
          Show this thread
        17. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 7 Aug 2020

          Prof. Jose-Luis Jimenez Retweeted Thread Reader Unroll Helper

          This is the unrolled version of thread:https://twitter.com/UnrollHelper/status/1291765883019436033 …

          Prof. Jose-Luis Jimenez added,

          Thread Reader Unroll Helper @UnrollHelper
          Replying to @thomasdickinson
          Hello, here is your unroll: @jljcolorado: 1/ Air cleaners: the good, the dubious, and the ugly With pandemic & major contribution of aerosol spread… https://threadreaderapp.com/thread/1291758303089852417.html … Have a good day. 🤖
          1 reply 18 retweets 67 likes
          Show this thread
        18. Prof. Jose-Luis Jimenez‏Verified account @jljcolorado 8 Aug 2020

          I didn't mention foggers with bleach or hydrogen peroxide. I don't like them either. Do not use when ppl present. Money better spent on HEPA, IMHO

          7 replies 12 retweets 78 likes
          Show this thread
        19. End of conversation

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