v4.17.4 Please send feedback to CAiMIRA-dev@cern.ch

Calculator

Virus data:
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Vaccinated? 💉

With booster?

Due to the lack of data, only the efficiency of the primary dose(s) is considered

Room data:
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Central heating system in use:
Ventilation data:
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Ventilation type:

Natural Ventilation

Single-sided ventilation is assumed in the model and is typically effective for room depths up to a depth 2.5 x the ceiling height. If these conditions are not met, the air exchange might not be homogenous producing an artificially lower risk further away from the window.



Window type:

Window open:
?

For the CO₂ fitting algorithm, the following input values will be considered:
  • Room volume (m³)
  • Total number of occupants
  • Presence transition times
CO₂ Fitting Algorithm
Upload a valid data file (.xls or .xlsx):
Download template

You may use the provided template and fill in the values.

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The dashed lines are suggestions for the ventilation transition times

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Room data:
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Fitting result

Ventilation values (ACH):



HEPA Filtration / Eq. ventilation:
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Face masks:
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Are masks worn when occupants are at workstations?

Type of masks used:
Event data:
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Conference/Training activities limited to 1 infected
Exposed person(s) presence:

Infected person(s) presence:

Short-range interactions (without masks):

The use of masks mitigates exposure at short-range. The analytical model with short-range interactions does not take mask wearing into account.

0 short-range interactions.

Short-range interactions

Activity breaks:
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Exposed person(s) breaks:
Lunch break:

Start:
Finish:
Coffee Breaks:


Duration (minutes):


Infected person(s) breaks:
Lunch break:

Start:
Finish:
Coffee Breaks:


Duration (minutes):



Coffee breaks are spread evenly throughout the day.



Quick Guide:
This tool simulates the airborne spread SARS-CoV-2 virus in a finite volume and estimates the risk of COVID-19 infection. It is based on current scientific data and can be used to compare the effectiveness of different mitigation measures.
Virus data:
SARS-CoV-2 covers the original "wild type" strain of the virus and three variants of concern (VOC):
  • Alpha (also known as B.1.1.7, first identified in UK, Sept 2020),
  • Beta (also known as B.1.351, first identified in South Africa, May 2020).
  • Gamma (also known as P.1, first identified in Brazil/Japan, Jan 2021).
  • Delta (also known as B.1.617.2, first identified in India, Oct 2020).
  • Omicron (also known as B.1.1.529, first identified in South Africa, November 2021).
Modify the default as necessary, according to local area prevalence e.g. for Geneva or Ain (France).
Ventilation data:
  • Mechanical ventilation = the HVAC supply of fresh air. Check the flow rates with the concerned technical department.
  • Natural ventilation = the type of window opening. The opening distance is between the fixed frame and movable part when open (commonly used values are window height of 1.6m and window opening between 0.15m and 0.6m). In case of periodic opening, specify the duration (e.g. 10 min) per hour.
  • HEPA filtration = the air flow of the device. The following values are based on the different fan velocities of a specific commercial device proposed by the HSE Unit:
    • Level 6 (max) = 430 m3/h (noisy),
    • Level 5 = 250 m3/h (ok w.r.t. noise, recommended),
    • Level 4 = 130 m3/h (silent),
    • Level 3 = 95 m3/h (silent).
Activity types:
The type of activity applies to both the infected and exposed persons:
  • Office = all seated, talking 33% of the time,
  • Small meeting (< 10 occ.) = all seated, talking time shared between all persons,
  • Large meeting (>= 10 occ.) = speaker is standing and speaking 33% of the time, other occupants are seated,
  • Call Centre = all seated, continuous talking,
  • Control Room (day shift) = all seated, talking 50% of the time,
  • Control Room (night shift) = all seated, talking 10% of the time,
  • Library = all seated, no talking, just breathing,
  • Laboratory = light physical activity, talking 50% of the time,
  • Workshop = moderate physical activity, talking 50% of the time,
  • Conference/Training (speaker infected) = speaker/trainer standing and talking, rest seated and talking quietly. Speaker/Trainer assumed infected (worst case scenario),
  • Conference/Training (attendee infected) = someone in the audience is infected, all are seated and breathing.
  • Gym = heavy exercise, no talking, just breathing.
Activity breaks:
  • If coffee breaks are included, they are spread out evenly throughout the day, in addition to any lunch break (if applicable).
Refer to Calculator App user guide for more detailed explanations on how to use this tool.

CAiMIRA is a risk assessment tool developed to model the concentration of viruses in enclosed spaces, in order to inform space-management decisions.

CAiMIRA models the concentration profile of virions in enclosed spaces with clear and intuitive graphs. The user can set a number of parameters, including room volume, exposure time, activity type, mask-wearing and ventilation. The report generated indicates how to avoid exceeding critical concentrations and chains of airborne transmission in spaces such as individual offices, meeting rooms and labs.

The risk assessment tool simulates the airborne spread SARS-CoV-2 virus in a finite volume, assuming homogenous mixing for the long-range component and a two-stage jet model for short-range, and estimates the risk of COVID-19 airborne transmission therein. The results DO NOT include other known modes of SARS-CoV-2 transmission, such as contact or fomite. Hence, the output from this model is only valid when the other recommended public health & safety instructions are observed, such as adequate physical distancing, good hand hygiene and other barrier measures.

The model used is based on scientific publications relating to airborne transmission of infectious diseases, dose-response exposures and aerosol science, as of February 2021. It can be used to compare the effectiveness of different airborne-related risk mitigation measures.

Note that this model applies a deterministic approach, i.e., it is assumed at least one person is infected and shedding viruses into the simulated volume. Nonetheless, it is also important to understand that the absolute risk of infection is uncertain, as it will depend on the probability that someone infected attends the event. The model is most useful for comparing the impact and effectiveness of different mitigation measures such as ventilation, filtration, exposure time, physical activity, amount and nature of close-range interactions and the size of the room, considering both long- and short-range airborne transmission modes of COVID-19 in indoor settings.

This tool is designed to be informative, allowing the user to adapt different settings and model the relative impact on the estimated infection probabilities. The objective is to facilitate targeted decision-making and investment through comparisons, rather than a singular determination of absolute risk. While the SARS-CoV-2 virus is in circulation among the population, the notion of 'zero risk' or 'completely safe scenario' does not exist. Each event modelled is unique, and the results generated therein are only as accurate as the inputs and assumptions.

CAiMIRA has not undergone review, approval or certification by competent authorities, and as a result, it cannot be considered as a fully endorsed and reliable tool, namely in the assessment of potential viral emissions from infected hosts to be modelled.

ARIA

Airborne Risk Indoor Assessment

WHO
Home
Publication
Systematic review results
Open Source repository
CO₂ Fitting Algorithm
1Context - Geographical location and date

Context - Geographical location and date

Please provide the date and location of the event/activity
If this information is not available, Geneva will be used as the default setting.

Date


Location

Country

The location and time enable to estimate outdoor temperature and humidity which can affect the natural indoor ventilation.

Step context-geographical-location-and-dateStep context-geographical-location-and-date
Step context-geographical-location-and-dateStep context-geographical-location-and-date
2Context - Temperature/Humidity
3SARS-CoV-2 variant
4Space dimension
5Duration
6Occupancy
7Host immunity
8Event details
9Mask - YES/NO
10Short range interactions - YES/NO
11Short range interactions
12Type of ventilation
13Ventilation - Mechanical
14Ventilation - Type of windows
15Ventilation - Windows dimensions
16Ventilation - Windows opening
17Ventilation - Number of windows
18Air filtration - YES/NO
19Air filtration - CADR

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ARIA v1.4.4-01040403

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Open Source Acknowledgements
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Disclaimer

Please click "Accept" to confirm that you have read and understand

The Airborne Risk Indoor Assessment tool (the “Tool”) enables users to assess SARS-CoV-2 airborne risk transmission in residential, public and health care settings and inform risk reduction measures. In using the Tool, users acknowledge and accept the Terms of Use as set out below.

Outputs are constrained based on editable parameters: This Tool includes assumptions about pathogen-specific features, pathogen-host interactions and human behaviors. For example, the viral load exhaled by an infected person, biological decay, the dose-response model, and interpersonal distance. All the included values are available through the systematic review results tab. Users can manually input other variables such as time, temperature, and occupancy to increase the output accuracy.
The model is stochastic and includes the uncertainties reported in the data extracted from the systematic review. The end result of the Tool returns the total Probability of Infection, taking into account the uncertainties tied to the parameters.

Limitations: The Tool is not meant to replace a comprehensive risk assessment.
The Tool is subject to inherent limitations and assumptions, which are important to acknowledge for a comprehensive understanding of the Tool’s scope and accuracy.
Complexity of Transmission Dynamics: The aerobiology of infectious particles and the transmission dynamics of viruses in humans are intricate and multifaceted. Various factors, including particle size distribution, environmental conditions, indoor air flows, and virus characteristics, can significantly impact the transmission process.
Variability in Data: The model relies on available scientific data and literature. However, there may be limitations in the quality and quantity of data for some variables, leading to potential biases and uncertainties in the results.
Parameter Values: The accuracy of the model depends on parameter values used for calculations. Despite efforts to extract and update these values, they are subject to ongoing research and may change over time, affecting the model's reliability.
Long-Range Transmission Assumption: The model assumes a well-mixed approach for long-range transmission, which may not fully represent real-world scenarios. Fluid dynamics simulations, while more precise, pose practical challenges in terms of computational capacity and expertise.
Short-Range Transmission: Short-range transmission may be influenced by other factors such as posture and airflow interactions, introducing additional complexity and uncertainty.
Host-Pathogen Interaction: Variables related to host-pathogen interaction, including viral load, dose-response, and host immunity, are influenced by multiple factors, making accurate estimation challenging. The model employs a probabilistic approach and the precautionary principle to address these limitations.
Post-Infection Immunity: The model currently considers only vaccine-induced immunity due to data limitations. Other post-infection immunity is not included for now, potentially leading to an overestimation of risk.
Number of Infectors: The model allows for calculations that consider multiple infectors, and the user must input the number of infected individuals attending an event, which requires an assumption on the part of the user.
Please be aware that this web application's results are presented as total probabilities, and the accuracy depends on the quality of data and statistical distributions. Regular updates may be necessary to account for evolving knowledge and data availability.
The use of this Tool should be accompanied by a critical understanding of these limitations, and it is advisable to consult with healthcare professionals and experts for a comprehensive assessment of SARS-CoV-2 transmission risk in specific contexts. This tool should not replace professional medical advice or public health guidelines.

General disclaimer
The Tool and the accompanying published material is being distributed “as is”, without warranty of any kind, either expressed or implied. The responsibility for the interpretation and use of the Tool and the material lies with the user. In no event shall WHO or CERN be liable for any damages arising from its use. WHO and CERN assume no liability or responsibility for any error or omissions in the information contained in the Tool or its functioning. WHO and CERN shall not be responsible for the compatibility of the Tool with any hardware or software, or issues related to the intrinsic characteristics of the Internet and connectivity. Access to the Tool may be interrupted or suspended without prior notice, in particular for the purpose of maintenance operations.

This is the 1.4.4-01040403 version of the tool: As more data become available, updated versions will be shared in an effort to regularly develop the tool and improve its functionality and assumptions.