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ViPER - Virus Particle Exposure in Residences


The web-based tool Virus Particle Exposure in Residences (ViPER) allows users to compare an individual scenario against multiple “what-if” scenarios related to particle exposure associated with a contagious visitor in the home. ViPER is a single zone indoor air quality and ventilation analysis tool developed by the National Institute of Standards and Technology (NIST) for evaluating an occupant’s relative exposure to virus-laden particles exhaled by a temporary contagious visitor inside the home. There’s also an option to evaluate the change in particle concentration. Behind the user interface of the tool is a database of 1,296 CONTAM simulation results, where each scenario is a variation on a set of input parameters such as home size, visit duration, and portable air cleaner speed, as well as mechanical ventilation and HVAC strategy. CONTAM ( is a leading indoor air quality modeling software tool also developed at NIST. For modeling capabilities that extend beyond ViPER, consider using FaTIMA ( or CONTAM.

Click here to access the ViPER Tool


The information of this webtool could support decisions that would help reduce exposure to a 1 μm particle generated by a contagious visitor. This webtool does not define levels of exposure considered to be safe or healthy, nor consider the impacts of these controls as part of broader risk reduction strategies that might be implemented by a resident.


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Created November 22, 2021, Updated November 23, 2021