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# System prepended metadata

title: 'Challenge 1: Ventilation'

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# Challenge 1: Ventilation

Recovery from the Pandemic: Hospitality & Leisure VSG
12th - 14th October 2021


## Group members:

Murat Mustafa (University College London)
Elpida Vangeloglou (London South Bank University)
Filipa Adzic (University College London)
Oliver Wild (University College London)
Paul Cropper (Loughborough University)
Ben Roberts (Loughborough University)
Maha Kaouri (Isaac Newton Institute)

## Problem outline

### Cambridge University Sports Centre


#### Overview
Operates the University Sports facilities and conducts oversight of University Sports Clubs. It has three main sites – University Sports Centre (indoor sports and gym), Fenner’s Cricket and Tennis Ground (including indoor cricket school), and Wilberforce Road Sports Ground (Athletics and Hockey). All of the sites have some indoor space, with the indoor space at sports grounds generally focused on function rooms and changing areas. The centre hosts approximately 60 sports clubs.


#### The Problem
Ensuring effective ventilation to reduce transmission of airborne viruses across all of the University Sports' indoor spaces. 

There are a wide variety of spaces, some with building management systems (BMS) and some naturally ventilated, with a wide variety of (sporting and non-sporting) activities taking place, and a wide variety of attendance levels.

There are also variable conditions with the BMS' operating differently in response to the varying indoor environment and outdoor weather conditions. Understanding the impact on temperature and climate control on ventilation is also of interest.

Control of BMS is restricted to the Facilities Management (FM) team. Users do not have direct control of building settings, such as temperature set-points or ventilation, so they have to submit requests to the FM team for changes to be made.

There is currently limited understanding of building operation and a lack of knowledge about things such as sensor locations.


#### The Desired Outcome
Cambridge University Sports Centre want to have effective controls and measures to ensure that all of their spaces meet ventilation standards, and that these be sustainable in the long-term.

### Independent Cinema Office (ICO)

The independent cinemas have different building structures such as historical and modern, with auditoria of different sizes. The ventilation systems in place also vary from cinema to cinema, and in general one of the following is in place:

1) Mechanical ventilation
2) Natural ventilation
3) No/unknown ventilation system

It would be beneficial for the ICO to understand what kind of guidance could be given to clients to support them in identifying whether they have adequate ventilation provision in their venues.

### UK Hospitality

There are many forms of ventilation in place across the hospitality sector, from opening windows to mechanical devices, each with a different cost and effectiveness.

It would be beneficial to understand:

1) What are acceptable risk levels?
2) What can businesses implement to ensure ventilation is effective at removing the virus from premises?
3) Cost-benefit of CO2 monitors?
4) What are the implications in winter?
5) Customer perception of ventilation – cold pubs and bars versus a perception of a safer environment?
6) How does this play out amongst different age groups?

## Questions for stakeholders

### Cambridge Sport Centre 

Our general advice is to gain an understanding of each building. Specifically, how they were intended to be used, how they are used now, how they were ventilated when first designed, how they are ventilated now, and if there have been any structural changes that could affect ventilation. We would then advise to install CO2 sensors in appropriate locations to monitor the effectiveness of the ventilation. 

If we can have architectural drawings (including floor plans, elevations, and photographs) we can help with understanding the buildings and indentyfing the possible locations for installation of sensors. This would give the approximate number of sensors needed, so budgeting for equipment could be planned.

If we could have a ventilation related drawings (both mechanical and natural) and photographs (both interior and exterior) we could provide some specific insights regarding what could be done if CO2 levels go above threshold values.

Please provide BMS data along with occupancy numbers if available. The air temperature, fresh air flow rates for each zone, the typical number of people in each zone the condition of re-circulation (on or off), heat recovery (on or off), and air conditioning information would be particularly relevant. 

It would be useful if you could identify operable windows (or any other types of ventilation opening), their approximate dimensions (size of opening), and types (i.e. top-hung/side-hung etc.). This would help us to approximate potential supply air flow rates from the windows or other openings. 

Whilst we are unable to recommend specific equipment, we can identify examples of CO2 monitoring equipment (brand and model) which we previously used and tested in Events Research Program (ERP), for consideration if and when Cambridge University Sports Centre decide to purchase CO2 loggers. Some sensors should be located in fixed positions within the breathing zone. Sensors that log data continuously and which can be accessed remotely via a dashboard are particularly useful. Doing so would allow instant notification when the CO2 levels exceeds threshold values. Note: When selecting a system for long term monitoring, consideration should be given to for regular calibration of sensors.


### Independent Cinema Office (ICO) (& UK Hospitality) 

The Independent Cinema Office has a large and varied stock of buildings which are ventilated by several different types of ventilation systems. Some of them have mechanical ventilation and some have natural ventilation, whilst others have limited knowledge of the ventilation provision. Therefore, as a first action, it would be critical to identify the venues with potential problems so that the efforts can be concentrated on those venues rather than visiting all of the venues individually. The questions introduced below can be used to compile a survey and ICO can distribute those surveys to identify the venues with potential ventilation problems. It is important to stress that the questions below are drafted for indicating the information required for identifying the venues with potential ventilation problems. The ICO might want to consider re-drafting the questions in appropriate format and processing through their ethical procedure before distributing to their members.  

The following questions have been designed in consultation with the ICO, but could be appropriate to other similar venue operators:

#### Suggested questions for identifying venues with potential ventilation problems

1) Is the venue operational (i.e. currently accepting customers)?
2) How is the building ventilated?
    a) Mechanically ventilated
    b) Naturally ventilated (i.e. via the opening of windows, doors, and passive vents)
    c) Mixed (i.e. both mechanical and natural) ventilation?
    d) Don't know
3) Is a trained employee responsible for managing the operation of the ventilation system?
4) Are there reports of complaints regarding indoor air quality (e.g. bad odours or a smell of stale air) from customers or staff? 
5) Is there a plan of action for when a staff member or customer complains about the indoor air quality or bad odours? If so, what is the plan?
6) Is there a plan of action for when a staff member or customer raises concerns regarding COVID-19 and the ventilation system? If so, what is the plan?
7) Are there specific locations where people congest (typically ancillary spaces to the main venus e.g. canteen, cafe, foyer, or bar etc.)?
8) Do you agree to take part in a field study where a group of experts installs CO2 monitors in your venue to assess the indoor air quality and adequacy of ventilation in the space?

Specifically for cinema venues, such as those members of the ICO, we would be interested in knowing:

1) Were the cinema buildings constructed as purpose-built cinemas or were many built for a different purpose, such as theatres or halls, and later converted into cinemas?
2) If so, how have the changes affected ventilation?
 
If you could provide examples of a variety of cinema spaces and more information (see the information requests made to Cambridge University Sports Centre) we can then provide more detailed insights and suggestions.


### Shakespeare's Globe

* Is advice needed about ventilation of winter venue?
 




## Scenarios

In this section, we will outline some scenarios from previous studies that may be relevant to the problem stakeholders.

Previous studies have shown that ancillary spaces to the main venues (e.g. canteens, cafes, bars etc.) are often overcrowded and not sufficiently ventilated. It is sugested that venues take extra care in those locations and segregate people into smaller groups and increase the air flow whenever possible to reduce airborne virus transmission risk. As shown in the figure below, average CO2 levels are high in a bar area zone marked "PT10" as this space was often overcrowded and not sufficiently ventilated. In comparison, auditorium zones PT2-PT8, PT16-PT19 and PT22-PT27 had good ventilation, as indicated on the graph.

Comparison of bar and auditorium spaces in a theatre:

![](https://i.imgur.com/TOBpOGi.jpg)


If there is an activity on stage involving physical effort (e.g. singing, shouting etc.), it is advised to leave some space between the stage and the spectators in the first few rows. 

An example of an auditorium with high occupancy but good ventilation:

![](https://i.imgur.com/hWdGzRo.jpg)


A similar problem was investigated in a previous study group on Unlocking Higher Education Spaces for lecture theatres (Page 10 of Ref 10).

## Guidance from literature

Ventilation is a key mitigation tool for aerosol airborne transmission of all respiratory viruses, including SARS-CoV-2. Mitigating infection risks from droplet and fomite transmission should include mask wearing, social distancing, and regular cleaning schedules. Measuring CO2 levels is a useful tool to evaluate ventilation in a space. However, it is not a proxy for risk of airborne transmission.


Ventilation operation suggestions and CO2 thresholds guidelines [1,3,4]

- A space with consistent CO2 value < 800ppm (absolute value) is a well ventilated space (this does not mean that it is COVID-19 risk free).

- A space with sustained high CO2 values (>1500ppm) is likely to indicate overcrowding or poor ventilation and mitigating actions are likely to be required.

- Based on current evidence, ventilation rates recommended in current UK building standards and guidance are considered adequate in most settings. The general recommendation is a supply of outdoor air of around 10 l/s per person, equivalent to approximately 800-1000ppm CO2. In cases of regular supply of fresh air below 5 l/s per person, which is expected to lead to >1500 ppm CO2, it is recommended that mitigating interventions (i.e. reducing occupancy density and/or increasing fresh air flow rates) should be introduced to reduce the infection risks. In spaces where aerosol generation could be higher (e.g. due to intense exercise, continuous talking, or a high chance of infectors being present) or where occupancy in the space lasts for a long time (e.g. a full working day), higher ventilation rates to maintain CO2 concentrations below 800 ppm are recommended.

![](https://i.imgur.com/3x7EFd0.png)

- **The room air should not be circulated unless absolutely necessary (e.g. the thermal comfort of the occupants can not be satisfied without re-circulation).**

- Ventilation should be provided at all times during the year and not only when the outside weather conditions are favourable. 

- In winter, a balance between airborne infection risk, energy demand, and thermal comfort can be achieved by modulating the output of the supply air flow rates. But the supply air flow rates should be not be lower than suggested values (mostly 8 – 10 l/s per person) at anytime during the year. 

- If the space is naturally ventilated, opening the windows will provide fresh air. In winter, the openings do not need be opened as wide as they are in summer, but nevertheless they should be opened. Operating all the windows with reduced opening angle will help with mixing in the domain. However if only low and high level openings exist in the space, high level openings should be opened first. Low level openings should be opened following the high level openings only if it is required (i.e. the CO2 targets are not reached and cold draughts will not cause thermal discomfort for occupants).

- In winter, natural ventilation can introduce larger air flow rates to spaces even with smaller openings. Therefore, operating the windows with smaller opening angles would serve the purpose. The benefits can be improved further if the space is purged even for a short time (e.g. a few minutes) during unoccupied time (e.g. between the meetings or performances).

- Demand control function of ventilation systems (i.e. reducing the ventilation flow rates according to the occupant density) should be disabled if the thermal comfort requirements could be met without the demand control function. Reducing the ventilation system CO2 threshold values will bypass the demand control and will aid with providing larger fresh air flow rates. 

- If the mechanical ventilation system has a rotary heat recovery unit, it is advisable to turn it off if the thermal comfort requirements of the occupants can be met without using the heat recovery unit. If the heat recovery is achieved by a plate or twin coil unit heat exchanger, it may remain operational. In both cases, suitable checks should be performed by a qualified personnel to make sure that the supply air is not contaminated by the recirculated air because of a leakage in the heat exchanger unit. 

- If there are zones within the building that cannot be ventilated by fresh outside air (e.g. basement and storage spaces), people's access to such places should be limited, especially if they will spend more than 30 minutes there.

- If a space in the building has split type air-conditioner units but does not have any means of ventilation, they should be only used for a short period of time. Similarly, if there is no obvious ventilation in a room or zone, building users should be discouraged from using that space. 

- Mechanical ventilation systems can be supported by natural ventilation by opening windows and providing extra fresh air into the space when the thermal comfort of the occupants is not compromised to unacceptable levels. 

- The air in spaces with unavoidable transient occupancy such as corridors and staircases should be purged regularly. 

- The furniture in spaces can be relocated (e.g. moving desks to further away from fresh air supplies) in heating seasons to keep the occupants away from the cold draughts. Also, dress codes can be more flexible, so people can wear warmer clothes indoors. These would help occupants to tolerate higher fresh air flow rates with lower temperatures and would help with achieving a balance between transmission risks, energy efficiency, and thermal comfort. It is also a possibility that disturbed thermal comfort might lead to shutting off the ventilation system completely which is undesirable for both infection risk and indoor air quality. 

- If the toilet blocks in the buildings are ventilated with either natural ventilation (e.g. a window) or mechanical ventilation (e.g. a fan), the windows or fans should remain open or operational throughout the day. However, if the toilet blocks have both windows and extract fans, the windows should be closed when the extract fans are operating.

- If the space is ventilated using natural ventilation, the windows should be opened at least 15 minutes prior to occupants' arrival. If the space is ventilated using mechanical ventilation, the ventilation system should be in operation (i.e. supplying air) an hour before the occupants arrive to the building and it should cease the supply air and hour after occupants leave the building.


If CO2 monitoring is employed, the following guidelines are recommended. The following table [1] gives an indication of the suitability of CO2 monitoring in different settings.

![](https://i.imgur.com/8cMhRJN.png)

Selecting CO2 sensors [1,3]

- CO2 monitoring with visual displays is more likely to lead to improved ventilation, as evidence suggests.

- CO2 sensors employing NDIR technology are widely shown to give more reliable readings.
 
- It is often more appropriate to measure CO2 concentrations relative to the background level rather than the absolute value in order to manage differences in sensor calibration offset. 

Locating CO2 sensors [1]

- Locating CO2 sensors effectively is important, as it will define the conclusions drawn about the ventilation within a room. Sensors should be placed at breathing height, away from windows, doors, ventilation openings and not close to individuals. Based on simulated data, at locations near the walls, where CO2 sensors are typically located, the range of variation within the interior of the room can be almost fully represented. Values that are particularly low (<500ppm) or high (>1500ppm) can be checked by moving the position of the monitor before taking action.


Reading CO2 measurements [1]

- Appropriate averaging CO2 periods (e.g. hourly or daily) should be used based on the purpose of the CO2 monitoring, rather than instantaneous readings; a short duration higher value may result from temporary higher occupancy or occupant proximity to the sensor and is not likely to indicate poor ventilation.  Shorter duration averaging may be appropriate for managing ventilation where short-term actions (e.g. opening a window) are used to improve the balance between purging of indoor pollutants and thermal comfort. For settings in which occupants typically reside for shorter durations, average concentrations determined over shorter time periods could be considered.

- A useful measure of the spaces as a whole can be given by presenting both average values and maximum values.

Assigning the responsibility [1]

- Behavioural impacts play a major role in the effectiveness of managing ventilation through CO2 monitoring. Unclear roles and responsibilities are often a barrier. We would recommend assigning the oversight and operation of the CO2 monitoring to (a) dedicated person(s) that understand the background (reading the below literature list will be helpful in that).

Building good habits [1]

- Providing training and resources to develop habits and routines that will bring lasting behaviours towards improved ventilation. For example, checking the monitor/ventilating the room when first entering it / leaving it / during breaks / when the device prompts attention.

Exposure Time 

- The overall cumulative exposure risk of an event depends on how much time people spend in the higher risk areas; for example, if a spectator at an outdoor football match spends the majority of their time at an indoor restaurant within the stadium they will have been at higher risk (Ref 5). Similarly, toilets at different venues can have high CO2 levels but time spent in those spaces is low; hence the risk is dependant both on ventilation and exposure time. 

Based on time spent in a space and CO2 levels, exposure was presented in terms of relative risk of being in a well-ventilated office space for 6 hours (Findings from ERP report, Ref 5).

![](https://i.imgur.com/7OZQ1GM.jpg)

Air cleaning technologies should be used if ventilation standards cannot be met (Ref 5,8).

- In-room air cleaners can be used when HVAC equipment equipment does not meet recommendations for ventilation and filtration, removal of contaminats near a source is needed or when higher risk activites occur.

- To assess whether air cleaning technologies are an appropriate measure for a space building operators are advised to refer to the relevant CIBSE Guidance (Ref 5). The Relative Exposure Index calculator (Ref 2 under "Useful Tools") can be used to assess the relative exposure index of a space by introducing basic inputs and comparing the performance with and without air cleaners.

Maintenance

- Ensure that maintenance checks of the mechanical systems take place at the recommended frequency by trained staff, as usually issues relate to technical defects. For example, changing filters, checking the quality of filters for misplacement or holes, etc. can have a direct impact on the air quality supplied in the space.


## Useful literature and bibliography

In this section, we will highlight some key literature/documentation that the problem stakeholders can use to inform their decisions on what type of ventilation systems should be in place.

1. https://www.gov.uk/government/publications/emg-and-spi-b-application-of-co2-monitoring-as-an-approach-to-managing-ventilation-to-mitigate-sars-cov-2-transmission-27-may-2021
2. https://www.gov.uk/government/publications/covid-19-ventilation-of-indoor-spaces-to-stop-the-spread-of-coronavirus/ventilation-of-indoor-spaces-to-stop-the-spread-of-coronavirus-covid-19
3. https://www.gov.uk/government/publications/emg-role-of-ventilation-in-controlling-sars-cov-2-transmission-30-september-2020
4. https://www.cibse.org/emerging-from-lockdown#1 - COVID-19: Ventilation
5. https://www.cibse.org/emerging-from-lockdown#1 - COVID-19: Air cleaning technologies
6. https://www.gov.uk/government/publications/events-research-programme-phase-i-findings/events-research-programme-phase-i-findings
7. https://www.ashrae.org/file%20library/technical%20resources/covid-19/core-recommendations-for-reducing-airborne-infectious-aerosol-exposure.pdf
8. https://www.ashrae.org/file%20library/technical%20resources/covid-19/in-room-air-cleaner-guidance-for-reducing-covid-19-in-air-in-your-space-or-room.pdf
9. https://www.ashrae.org/file%20library/technical%20resources/covid-19/guidance-for-small-temporary-dining-structures.pdf
10. https://gateway.newton.ac.uk/sites/default/files/asset/doc/2007/Unlocking%20HE%20Spaces%20July%202020_small_0.pdf

## Useful Tools

There are a number of tools available for the assessment of airborne transmission risk and relative exposure to SARS-CoV-2. Some of these tools may require a good understanding of the scientific background, while others may be more simple. The tools should be used with caution when assessing large spaces, as they typically assume well-mixed conditions, which is unlikely the case in large spaces.
1. https://docs.google.com/spreadsheets/d/16K1OQkLD4BjgBdO8ePj6ytf-RpPMlJ6aXFg3PrIQBbQ/edit#gid=519189277
Estimates COVID-19 transmission risks based on room volume, ventilation rate etc. An introduction to the tool can be found here: 
https://cires.colorado.edu/news/covid-19-airborne-transmission-tool-available
2. https://www.cibse.org/emerging-from-lockdown#1 - COVID-19: Relative Exposure Index calculator
3. https://www.nist.gov/services-resources/software/fatima - Fate and Transport of Indoor Microbiological Aerosols (FaTIMA) allows for the determination of the indoor fate of microbiological aerosols associated with ventilation, filtration, deposition and inactivation mechanisms.
4. https://www.rehva.eu/covid19-ventilation-calculator - To estimate the effect of ventilation on COVID-19 airborne transmission
5. https://www.rehva.eu/activities/covid-19-guidance/covid-19-multi-room-calculator - COVID-19 Multi-room and Recirculation Calculator for HVAC systems operational strategy assessment for reducing infection risk in buildings


## Pictures and Figures
Installation example in the lower circle of an auditorium:
![](https://i.imgur.com/rLI9R9m.png)
Installation example in the upper circle of an auditorium:
![](https://i.imgur.com/WmxuO5L.png)

Installation example in auditorium:
![](https://i.imgur.com/zJhg5LN.jpg)

When installing the sensors, command tape was used on walls. Under auditorium seat, command tape was used with cable ties.