COVID-19 infection risk calculator

free tool

indoor infection risk calculator for COVID-19

Using the Wells-Riley equation, this simple analysis tool helps building operators understand:

  • the contribution of the HVAC system to the overall risk of spreading the virus and 
  • different operation strategies to decrease the risk.

The top strategies include:

    • increasing the outside air fraction,
    • increasing the overall ventilation recirculation rate,
    • implementing additional filtering, or air purification methods.
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Download the infection risk calculator using the form below.

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want to reduce the risk of COVID-19 infection?

video tutorial

how to use the calculator

covid-19 infection risk calculator ventilation building healthy workplace covid-19 operations kw engineering

from our engineers

developer notes

We’ve done a diligent QC of implementing the Wells-Riley equation for estimating the infection risk of COVID-19, an equation also used by ASHRAE.

But it’s complicated and if you see this tool respond in a manner that is counterintuitive then let us know.

As an alternative to traditional air conditioning systems, consider direct evaporative cooling as a means of cooling incoming air and adding hydration to the space as well. It provides cooling, fire protection, and air cleaning at only the cost of water.


We’ve made assumptions about critical constants in the calculator that we believe are conservative but currently have a high degree of error.

Key among them is the quanta assumption for COVID which at time of publishing has a high degree of error associated with it.

We’ve assumed 48 as our quanta constant in this implementation. If you’d like a version of this calculator that allows you to adjust the assumption for quanta, let us know.

outdoor air impacts

free tool

Outside Air Ventilation Load Estimator

Learn more about the impacts on your building load when adjusting outside air percentages with our free ventilation load estimator. 

indoor workplace covid-19 hvac outdoor air load calculator kw engineering
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