{"id":830,"date":"2020-09-15T12:57:46","date_gmt":"2020-09-15T19:57:46","guid":{"rendered":"http:\/\/wordpress.kpu.ca\/camidanser\/?p=830"},"modified":"2020-10-15T21:04:09","modified_gmt":"2020-10-16T04:04:09","slug":"artilce-review-ventilation-control-for-airborne-transmission-of-human-exhaled-bio-aerosols-in-buildings","status":"publish","type":"post","link":"https:\/\/wordpress.kpu.ca\/camidanser\/artilce-review-ventilation-control-for-airborne-transmission-of-human-exhaled-bio-aerosols-in-buildings\/","title":{"rendered":"Ventilation control for airborne transmission of human exhaled bio-aerosols in buildings"},"content":{"rendered":"\n

Article Review: <\/strong>Ventilation control for airborne transmission of human exhaled bio-aerosols in buildings – Journal of Thoracic Diseases<\/p>\n\n\n\n

\"Three
Three key elements of ventilation affecting the airborne transmission.<\/figcaption><\/figure>\n\n\n\n

Introduction<\/strong><\/p>\n\n\n\n

  • Airborne transmission mostly in indoor environments, where ppl spend 90% of time<\/li>
  • Growing urbanization, overcrowding in large cities, growing transportation networks spread faster <\/li>
  • SARS outbreak 2003, hong kong hospital hit hard most likely due to insufficient ventilation system in ward 8A <\/li>
  • Increasing ventilation rates in classrooms, offices, homes effective strategy in controlling airborne diseases  <\/li>
  • \u201cVentilation is defined as the supply\/distribution or removal of air from space by mechanical or natural means\u201d <\/li>
  • Supply outdoor air, remove excess heat, humidity and contaminants <\/li>
  • Goal: pathogen-free fresh air<\/li>
  • Air flow controlled from \u2018clean zones\u2019 to \u2018dirty zones\u2019 <\/li><\/ul>\n\n\n\n

    The mechanism of airborne infection<\/strong><\/p>\n\n\n\n

    • Path of airborne transmission via droplet nuclei 
      •  Sneezing, coughing, speaking, singing, breathing<\/li>
      • 40k – 2mil  droplets from a sneeze<\/li>
      • ~100000 from cough<\/li>
      • ~3000 loud speaking<\/li><\/ul><\/li>
      • \u201cDroplet spread refers to the passage of pathogens from a source to a susceptible through large droplets.\u201d <\/li>
      • \u201cAirborne transmission refers to the passage of pathogens from a source to susceptible through airborne aerosols\u201d
        • Droplet nuclei (residues of dried out droplets)<\/li><\/ul><\/li>
        • Risk of short-range airborne infections > risk of long-range airborne infections <\/li><\/ul>\n\n\n\n

          The impact of ventilation rate<\/strong><\/p>\n\n\n\n

          • Higher ventilation rates also increases energy costs, NEED FOR balance between decreasing cross infection risk and energy consumption\u00a0<\/li>
          • Minimum ventilation rate in isolation rooms is 12 air change per hour (ACH)<\/li>
          • 6 ACH in CDC guidelines, doubled after SARS, only 1 ACH in commercial buildings<\/li>
          • Wells-Riley equation to predict risk of airborne infection<\/li>
          • Natural ventilation large ventilation rates w\/low energy consumption, larger ventilation rates than mechanical ventilation<\/li>
          • Proven that increasing ventilation rate reduces risk of cross infection for long-range airborne infections\u00a0<\/li>
          • Effect of ventilation for droplet-borne transmitted diseases less known\u00a0<\/li><\/ul>\n\n\n\n

            The impact of flow direction<\/strong><\/p>\n\n\n\n

            • Directional flow achieved through pressure differences <\/li>
            • Isolation rooms use positive pressure to keep the surrounding contaminated air out<\/li>
            • AII rooms use negative pressure to prevent droplet nuclei from infected patients from exiting the room (negative pressure only maintained by keeping windows and doors closed) <\/li>
            • Field studies: 50% of tested isolation rooms failed to provide negative pressure 
              • Caused by \u201cinadequate reliability of pressure monitoring and controlling devices, strong diffuser flow directed at door, interaction with other exhaust ventilation systems and poor airtightness of the suspended false ceiling\u201d  <\/li><\/ul><\/li><\/ul>\n\n\n\n

                The impact of airflow pattern<\/strong><\/p>\n\n\n\n

                • 3 types of common ventilation; mixing ventilation, downward ventilation, displacement ventilation  <\/li><\/ul>\n\n\n\n
                  \n\n\n\n

                  Source: Qian, H., & Zheng, X. (2018). Ventilation control for airborne transmission of human exhaled bio-aerosols in buildings. Journal of thoracic disease, 10(Suppl 19), S2295\u2013S2304. https:\/\/doi.org\/10.21037\/jtd.2018.01.24<\/p>\n","protected":false},"excerpt":{"rendered":"

                  Article Review: Ventilation control for airborne transmission of human exhaled bio-aerosols in buildings – Journal of Thoracic Diseases Introduction Airborne transmission mostly in indoor environments, where ppl spend 90% of time Growing urbanization, overcrowding in large cities, growing transportation networks spread faster  SARS outbreak 2003, hong kong hospital hit hard most likely due to insufficient […]<\/p>\n","protected":false},"author":374,"featured_media":831,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17,23,59],"tags":[12,15,14,16,13],"class_list":["post-830","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-article-reviews","category-research","category-ventilation","tag-airborne-diseases","tag-bio-aerosols","tag-exhaled","tag-isolation-ward","tag-ventilation"],"_links":{"self":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/830","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/users\/374"}],"replies":[{"embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/comments?post=830"}],"version-history":[{"count":10,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/830\/revisions"}],"predecessor-version":[{"id":1106,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/830\/revisions\/1106"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/media\/831"}],"wp:attachment":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/media?parent=830"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/categories?post=830"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/tags?post=830"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}