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. 2023 Mar;44(2):113-133.
doi: 10.1177/01436244221137995. Epub 2022 Dec 16.

Measurement and rapid assessment of indoor air quality at mass gathering events to assess ventilation performance and reduce aerosol transmission of SARS-CoV-2

Liora Malki-Epshtein  1 , Filipa Adzic  1 , Ben M Roberts  2 , Elizabeth Abigail Hathway  3 , Christopher Iddon  4 , Murat Mustafa  5 , Malcolm Cook  2
Affiliations

Measurement and rapid assessment of indoor air quality at mass gathering events to assess ventilation performance and reduce aerosol transmission of SARS-CoV-2

Liora Malki-Epshtein et al. Build Serv Eng Res Technol. 2023 Mar.

Abstract

To assess risk factors for COVID-19 transmission and address the closure of mass gathering events since March 2020, the UK Government ran the Events Research Programme (ERP), following which it reopened live events in sports, music, and culture in July 2021. We report the rapid post-occupancy evaluation of Indoor Air Quality (IAQ) and associated long-range airborne transmission risk conducted in the Environmental Study of the ERP. Ten large venues around the UK were monitored with CO2 sensors at a high spatial and temporal resolution during 90 events. An IAQ Index based on CO2 concentration was developed, and all monitored spaces were classified in bands from A to G based on their average and maximum CO2 concentrations from all events. High resolution monitoring and the IAQ Index depicted the overall state of ventilation at live events, and allowed identification of issues with ventilation effectiveness and distribution, and of spaces with poor ventilation and the settings in which long-range airborne transmission risk may be increased. In numerous settings, CO2 concentrations were found to follow patterns relating to event management and specific occupancy of spaces around the venues. Good ventilation was observed in 90% of spaces monitored for given occupancies. Practical applications: High-resolution monitoring of indoor CO2 concentrations is necessary to detect the spatial variation of indoor air quality (IAQ) in large mass gathering event venues. The paper summarises COVID-19 ventilation guidance for buildings and defines a methodology for measurement and rapid assessment of IAQ during occupancy at live events that can be implemented by venue managers. Comparisons of the CO2 concentrations measured during the events identified the spaces at high risk of long-range transmission of airborne pathogens. Building operators should be mindful of the ventilation strategies used relative to the total occupancy in different spaces and the occupant's activities.

Keywords: CO2 monitoring; COVID-19; indoor air quality; infection control; post-occupancy.

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Conflict of interest statement

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
Installation of CO2 sensors at Ascot racecourse. Zones monitored are marked in yellow, and sensors are marked in red. (a) Parade Ring Restaurant (b) Private boxes.
Figure 2.
Figure 2.
The number of spaces across the ten monitored venues aggregated by air quality bands: (a) Spatial and temporal Average and (b) Maximum CO2 values. Data includes all venues and events from ERP Phases I, II and III. (Figures reproduced following the published figures in28 following a full and final analysis of all events where data was collected).
Figure 3.
Figure 3.
Average and Maximum CO2 values measured in two large venues (a1) and (a2) O2 Arena (b1) and (b2) Wembley Stadium.
Figure 4.
Figure 4.
Monitored air quality in toilets, corridors, lifts, stairwells (small, enclosed, short occupancy) at all ERP events, separated into Air Quality bands. (a) Average CO2; (b) Maximum CO2; (c) CO2 Time-Series in a single toilet at a high capacity event at Wembley Stadium.
Figure 5.
Figure 5.
Ventilation distribution at a small theatre as observed from 44 CO2 sensors around the space at varying occupancies. The black line presents the spatial average in the auditorium (mean). (a), (b), and (c) are events held on different dates at different occupancies of, respectively: ∼30%, ∼60%, and ∼90%. Full occupancy at this theatre is 980 seats
Figure 6.
Figure 6.
Measured CO2 concentration from a subset of sensors. Two sensors for each of the four zones. Dashed lines denote a sensor on the side of the building that has door openings. (a) Bramley Moore Dock Warehouse Nightclub Event 1; (b) Nightclub Event 2; (c) Nightclub monitored zones map with numbered sensors.
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