McKeon Group: Heating, Ventilation & Air-Conditioning Systems in the Context of COVID-19

McKeon Group: Heating, Ventilation & Air-Conditioning Systems in the Context of COVID-19

14/08/2020

Earlier this summer the European Centre for Disease Control (ECDC) published its guidance document on the ventilation of indoor spaces: ‘Heating, Ventilation & Air-Conditioning Systems in the Context of COVID-19’ https://www.ecdc.europa.eu/sites/default/files/documents/Ventilation-in-the-context-of-COVID-19.pdf

This guidance is designed to assist public health authorities in EU/EEA countries and in the UK to navigate their ongoing pandemic responses. It is unsurprising that an evidence-based study into the transmission of the virus within closed spaces was prioritised by the ECDC and it was inevitable that this would focus on the role of heating, ventilation and air-conditioning (HVAC) systems.

As most people will be aware, heating, ventilation and air-conditioning (HVAC) systems are used to provide and regulate consistently comfortable environmental conditions, such as temperature and humidity. It ensures that the air circulating inside the space is clean and of a good quality. At its simplest, ventilation systems provide clean air by exchanging and filtering indoor and outdoor air. Contemporary air-conditioning systems are generally part of integrated HVAC systems, unlike the more traditional or dated stand-alone air-conditioning units in older domestic settings that people might be familiar with.

Poor indoor ventilation has long been linked with increased transmission of a range of infections, including respiratory infections. Already, there have been numerous COVID-19 transmission events linked to enclosed spaces (including pre-symptomatic cases). Notwithstanding this, the role of ventilation in preventing COVID-19 transmission is not well-defined. While the guidance document lists incidents of indoor and outdoor transmission, outdoor transmissions are significantly fewer, and the authors acknowledge that the length of time people are in close physical contact played the most important role in spreading COVID-19.

The guidance document cites several studies that have addressed the role of ventilation in COVID-19 outbreaks, “three outbreaks involved an index case that was reported to be pre-symptomatic, and ventilation in an enclosed space, aided by air conditioning”. Also, “the authors of a pre-print manuscript describing two other outbreaks from China in January 2020 attribute air conditioning systems using a re-circulating mode as a probable aid to transmission”.

According to the guidance document, High Efficiency Particulate Air (HEPA) filters have demonstrated good performance with particles of the SARS- Cov-2 virus size (approximately 70−120 nm). Significantly, there is currently no evidence to date of “human infection with SARS-CoV-2 caused by infectious aerosols distributed through the ventilation system ducts of HVACs”. The document concludes that:

~ 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 and stand-alone air-conditioning units if air is recirculated.

~ Air flow generated by air-conditioning units may facilitate the spread of droplets excreted by infected people longer distances within indoor spaces.

~ 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.

For anyone with an interest in learning more about this, it is definitely worth reading the ECDC guidance document in full. 

Download the PDF document ‘Heating, Ventilation & Air-Conditioning Systems in the Context of COVID-19’  in full here: https://www.ecdc.europa.eu/sites/default/files/documents/Ventilation-in-the-context-of-COVID-19.pdf

About McKeon Group:

Established in 1950, this year marks the 70th anniversary of McKeon Group, which remains a family business. ISO certified for more than two decades, McKeon Group offers expert construction, fitout and building services. The Group delivers projects, services and maintenance across a range of sectors for State, local authority, FDI and private clients. For more information, contact: www.mckeon.ie