{"id":1133,"date":"2020-10-15T20:52:55","date_gmt":"2020-10-16T03:52:55","guid":{"rendered":"http:\/\/wordpress.kpu.ca\/camidanser\/?p=1133"},"modified":"2020-10-15T21:03:35","modified_gmt":"2020-10-16T04:03:35","slug":"heating-ventilation-and-air-conditioning-systems-in-the-context-of-covid-19","status":"publish","type":"post","link":"https:\/\/wordpress.kpu.ca\/camidanser\/heating-ventilation-and-air-conditioning-systems-in-the-context-of-covid-19\/","title":{"rendered":"Heating ventilation and air conditioning systems in the context of covid-19"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><strong>Technical Report &#8211; <\/strong>European Centre for Disease Prevention and Control <\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Evidence for transmission in closed spaces and role of HVAC systems <\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>HVAC used to provide comfortable environmental conditions (temperature and humidity) and clean air to indoor spaces <\/li><li>air-conditioning can be integrated with HVAC or stand alone, in which case air is recirculated <\/li><li>COVID-19 mostly thought to be transmitted via large respiratory droplets, increasing number of outbreaks reports point to role of aerosols in transmission<\/li><li><strong>aerosols &#8211; <\/strong>consists of small droplets and droplet nuclei, sustained in air for longer than large droplets<\/li><li>COVID-19 transmission most effective in crowded, confined indoor spaces (workplaces, indoor events) <\/li><li><strong>study of 318 outbreaks in China, only 1 did NOT occur in an indoor space<\/strong><\/li><li>outdoor spaces also have risk of transmitting COVID-19, especially where there are crowds of people<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><em>2.5 hour choir practice in Washington, US, there were 32 confirmed and 20 probable secondary COVID-19 cases among 61 participants (85.2%).<\/em> (p.2)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><em>In an epidemiological investigation at a call centre in South Korea, there was an attack rate of 43.5% among 216 employees on the ninth floor of the call centre, indicating extensive transmission in a crowded indoor workplace environment<\/em>. (p.2)<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>&#8220;&#8230;the length of time people were in contact played the most important role in spreading of COVID-19&#8230;&#8221;<\/p><\/blockquote>\n\n\n\n<ul class=\"wp-block-list\"><li>not yet possible to confirm role of physical proximity and direct contact, and possibility of indirect transmission through contaminated surfaces, fomites and aerosols<\/li><li>potential for <strong>publication bias<\/strong>, less coverage on negative findings<\/li><\/ul>\n\n\n\n<ul class=\"wp-block-list\"><li>several studies address <strong>role of ventilation with COVID-19<\/strong> <\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><em>In a restaurant outbreak in Guangzhou, China, there were 10 cases across three families [14]. They developed symptoms between 26 January and 10 February 2020, having eaten lunch on 23 January at the same restaurant, which is a five-floor building without windows. Their tables were more than a metre apart. The index case was pre-symptomatic, developing a fever and cough that evening. The <strong>secondary cases were sitting along the line of airflow generated by the air-conditioning<\/strong>, while <strong>diners sitting elsewhere in the restaurant were not infected<\/strong>. The authors of the report attribute transmission to the spread of respiratory droplets carrying SARS-CoV-2 via the airflow generated by the air-conditioning.<\/em> (p.2)<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\"><p>air conditioning systems using a re-circulating mode attributes as a probable aid to transmission<\/p><\/blockquote>\n\n\n\n<p class=\"wp-block-paragraph\"><em>The first outbreak was associated with a 150-minute event at a temple. The index case, who had previously visited Wuhan, was pre-symptomatic until the evening after the event. The attack rates in the outbreak were highest among those who shared a <strong>100-minute bus ride with the index case (23 out of 67 passengers; 34%)<\/strong>. <strong>Passengers sitting closer to the index case did not have a statistically higher risk of COVID-19<\/strong> than those sitting further away. However, all <strong>passengers sitting close to a window remained healthy,<\/strong> with the exception of the passenger sitting next to the index case. This supports the hypothesis that the airflow along the bus facilitated the spread of the virus. In contrast, there were seven COVID-19 cases among 172 other people who attended the same 150-minute temple event, all of whom described having had close contact with the index case.<\/em> (p.2)<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>high efficiency particulate air (HEPA) filters demonstrated good performance with SARS-Cov-2 virus particle size<\/li><li>used in aeroplanes and healthcare settings<\/li><li>although role of use of HEPA filters outside healthcare setting in controlling transmission is unclear<\/li><li>in large commercial aeroplanes: mixing ventilation systems was highest risk, conventional displacement was lowest risk <\/li><li>recommended <strong>personalized ventilation systems for airline cabins, best for thermal comfort while reducing infection risk<\/strong><\/li><\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">Available evidence indicates that:<\/h4>\n\n\n\n<ul class=\"wp-block-list\"><li>Transmission of COVID-19 commonly occurs in closed indoor spaces.<\/li><li>There is currently no evidence of human infection with SARS-CoV-2 caused by infectious aerosols distributed through the ventilation system ducts of HVACs. The risk is rated as very low.<\/li><li>Well-maintained HVAC systems, including air-conditioning units, securely filter large droplets containing SARS-CoV-2. It is possible for COVID-19 aerosols (small droplets and droplet nuclei) to spread through HVAC systems within a building or vehicle and stand-alone air conditioning units if air is recirculated.<\/li><li>Air flow generated by air-conditioning units may facilitate the spread of droplets excreted by infected people longer distances within indoor spaces.<\/li><li>HVAC systems may have a complementary role in decreasing transmission in indoor spaces by increasing the rate of air change, decreasing recirculation of air and increasing the use of outdoor air.<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Guidance<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Organizers and administrators should apply the following preventative measures:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>physical distancing <\/li><li>meticulous hand hygiene<\/li><li>respiratory etiquette <\/li><li>appropriate use of face masks, if required for staff, and in areas where physical distancing cannot be maintained due to structural or functional impediments<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Building administrators: <\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>maintain HVAC systems according to manufacturer&#8217;s instructions, particularly in regards to cleaning and changing air filters (no benefit or need for additional maintenance cycles in relation to COVID-19) <\/li><li>avoid use of energy-saving options such as demand-controlled ventilation controlled by timer or CO2 detectors <\/li><li>direct air flow directed away from people to avoid pathogen distribution from infected subjects <\/li><li>avoid use of recirculation in HVAC systems <\/li><li>ensure number of air exchanges per hour is in accordance with minimum ACH according to building regulations <\/li><li><strong>increasing ACH will reduce risk of transmission in closed spaces, <\/strong>achieved through natural or mechanical ventilation <\/li><\/ul>\n\n\n\n<ul class=\"wp-block-list\"><li>technical specifications and standards regarding mechanical ventilation and reducing the risk of COVID-19 in closed spaces still needs to be defined <\/li><li>including category of room or location type; size, degree of enclosure, non-mechanical ventilation, purpose of room <\/li><li>technical specifications regarding logistical arrangement (physical placement of mechanical ventilation systems) needs to be informed by scientific evidence and technical expertise <ul><li>considerations: expected number of users, types of user, user activity<\/li><\/ul><\/li><li>general rule, mechanical ventilation should be arranged as to avoid direct air flow on stationary persons<\/li><\/ul>\n\n\n\n<hr class=\"wp-block-separator is-style-wide\" \/>\n\n\n\n<p class=\"has-small-font-size wp-block-paragraph\">Source: ECDC. (2020, June 22). <em>Heating, ventilation and air conditioning systems in the context of Covid-19<\/em> (Rep.). Retrieved October 15, 2020, from European Centre for Disease Prevention and Control. Retrieved from https:\/\/www.ecdc.europa.eu\/sites\/default\/files\/documents\/Ventilation-in-the-context-of-COVID-19.pdf<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Technical Report &#8211; European Centre for Disease Prevention and Control Evidence for transmission in closed spaces and role of HVAC systems HVAC used to provide comfortable environmental conditions (temperature and humidity) and clean air to indoor spaces air-conditioning can be integrated with HVAC or stand alone, in which case air is recirculated COVID-19 mostly thought [&hellip;]<\/p>\n","protected":false},"author":374,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17,23,59],"tags":[55,58,53,57,30,29,56,54],"class_list":["post-1133","post","type-post","status-publish","format-standard","hentry","category-article-reviews","category-research","category-ventilation","tag-aerosols","tag-air-exchange-rate","tag-covid-19","tag-hvac","tag-mechanical-ventilation","tag-natural-ventilation","tag-respiratory-droplets","tag-transmission"],"_links":{"self":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/1133","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=1133"}],"version-history":[{"count":4,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/1133\/revisions"}],"predecessor-version":[{"id":1138,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/posts\/1133\/revisions\/1138"}],"wp:attachment":[{"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/media?parent=1133"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/categories?post=1133"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wordpress.kpu.ca\/camidanser\/wp-json\/wp\/v2\/tags?post=1133"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}