Note: Determining the true value of the mixing factor is difficult and requires special equipment to measure air flows and conduct tracer gas decay testing. Thus, conservative estimates of k are often used (as described above). Also, the addition of an air cleaning device (e.g., an in-room HEPA filtration unit) within the same room will reduce the wait time. The flow rate from the air cleaning device can be added to Q determined above, which will increase the overall ACH in the room. The air movement created by the air cleaning device can also decrease the value of k. Together, the increased ACH and decreased k can help substantially reduce wait times. See Example 2 at the bottom of FAQ #5 for more information, including an example of the calculations."}},{"@type": "Question","name": "3. Can ventilation filters effectively capture SARS-CoV-2 viral particles?","acceptedAnswer": {"@type": "Answer","text": "Yes, filters with higher collection efficiencies can provide significant reductions in viral particle concentrations.