This tool uses modeling data from the National Institute of Standards and Technologyexternal icon. The results are estimates and might not be exact in the real world. Our model assumes a visitor is staying for 4 hours in a 1,000 square-foot space and is not wearing a mask. This size is used because 1,000 square feet is the size of an average one-bedroom apartment in the United States, or about one floor of a larger home. The particle reduction is calculated based on levels that would be in the air at the end of the visit. If the “Open Window” option is selected as “Yes,” the tool assumes one single open window. All scenarios are compared against a scenario with no open windows, no HEPA air cleaner, and no HVAC system use.

For this model, a “premium” filter is based on one rated for MERV 13 filtration and “regular” filter is based on MERV 6 filtration. Learn more about HVAC filters and portable air cleaners. Visit Ventilation in Buildings (item #3 in Ventilation FAQs) to learn more about MERV ratings.

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