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

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.

Airborne infections related to virus aerosol contamination at indoor cultural venues: Recommendations on how to minimize

“…Other authors [83] also assess the air quality at singing events on the basis of 800 ppm CO 2 . A four‐stage CO 2 concept between <950 (high IAQ) and >1750 ppm (low IAQ) is proposed in an English publication [83]. Overall, it can be concluded that controlling the supply and exhaust air based on CO 2 measurements is an effective preventive measure against airborne infections at cultural events [84].…”

“…Modeling study [53] Sociocultural events Non-randomized controlled study [67] Chorus rehearsal Estimation of infectious quanta [56] Wind instruments Risk of spreading infectious particles [57] Concert hall Evaluation of the infection risk using mannequins [58,59] Indoor sports and cultural events simulation study to estimate the burden of disease under conditions of controlled epidemics [60] Mass gatherings Effectiveness of public health measures [68] Mass sporting and cultural events Use of interviews and questionnaires to describe the potential public health impact [70] Singing event Evaluation of safer singing practices [62] Live concert Randomized controlled trial of attendees [63] Indoor live concert Screening of attendees for SARS-CoV-2 antigen before the event [65,66] Indoor live events Measurement of CO 2 and viral RNA [69] Indoor live events High resolution CO 2 monitoring [82] Concert events Assessment of SARS-CoV-2 transmission using contract-tracing data [61] Carnival Seroepidemiological observational study [72] Visitor's point of view Online study with persons, who regularly attended events before the pandemic [73] Sport events Assessment of the suitability and feasibility of a hygiene concept [71] halls have grandstands, where the stage can also be in the middle. The third phase begins after the end of the performance and ends when all guests have left the venue.…”

“…Their suitability could be demonstrated, for example, by measurements in local public transport [80,81]. Moreover, high-resolution measurements (determination of CO 2 in intervals of about 1 min) enable the situation at live events to be monitored and are thus useful for a quick assessment of the distribution and effectiveness of the ventilation [82]. In a Spanish publication [81], the criterion is 800 ppm carbon dioxide (which is applied e.g., in European standards for the regulation of indoor ventilation systems in nonresidential buildings) instead of 1000 ppm.…”

Digital-twin-controlled ventilation for real-time resilience against transmission of airborne infectious disease in an indoor food court

“…The importance of considering the tempo-spatial variations for PI or its proxies in indoor settings had been documented in studies of airborne infection risks in vehicle cabins, 39,53,54 offices, 55 grocery stores 56 and auditoriums and nightclubs. 57 In addition, the assessment can also be used to identify the transient safe zones during the disruption. This is especially important for larger spaces with less well-mixed air, and the assessment could inform evacuation routes in the context of emergencies involving acutely hazardous air contaminants.…”

SARS-CoV-2 airborne infection risk in venues with different ventilation strategies – a comparison between experimental, numerical and analytical approaches

“…Although venue studies on the risk of airborne disease transmission have increased since the COVID-19 pandemic, a comprehensive risk assessment comparing and classifying different ventilation concepts with regard to their risk of transmitting infectious aerosols is still lacking. The only large-scale monitoring study analysed the ventilation effectiveness in up to 10 differently sized and ventilated theatres during 90 regular events with spectators using CO 2 sensors [26][27] .…”