v4.10 Please send feedback to CAiMIRA-dev@cern.ch

Calculator

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.