Abstract Americans newly infected with SARS-CoV-2 (SC2) are directed to isolate at home with care provided by household members. Isolation from others may be difficult to maintain for 2 weeks, especially in economically challenged households without enough space to create a private sick room and bathroom. The CDC recommends that at-home patients and their caregivers use makeshift facemasks for care-giver protection. They do not address the possibility of virus spread via smaller particles that are not captured by improvised facemasks. Accumulating evidence supports the significance of patient-generated aerosols, with and without ambient PM, in the transmission of SC2 infection, but haven’t been subject to controlled study. U.S. PM2.5 concentrations are linked to a 15% increase in COVID-19 deaths per ?g/m3 of PM2.5, suggesting an interaction between the two stressors. Thus, we plan to quantify SC2 in different PM fractions in home isolation rooms of newly diagnosed individuals Moreover, a common recommendation to reduce indoor aerosol exposures is filtration, and based on our experience we plan a crossover trial of air cleaners in home isolation rooms. We hypothesize that portable indoor particle filters will reduce both airborne PM and associated viral particle concentrations in the air around patients. We aim to test this hypothesis by enrolling 20 individuals from our employee health clinics with newly diagnosed SC2 infections in a cross-over randomized trial of home air cleaners. These will be continuously operated alternately for two consecutive 24-hour cycles, one cycle with a HEPA filter, and the other with a sham filter. Size selective impactors in the isolation room will elucidate particle sizes most associated with virus. Samplers will allow capture of PM2.5, PM coarse (10-2.5), and >PM10 fractions. In both the isolation room and the main living area we will collect total inhalable particles (d<100 µm) at 10 L/min. These samples will be used in initial analyses to check if there is sufficient viral RNA in individual impactor stages for reliable detection and quantification. Concentrations of PM and virus will be compared between filtered and sham conditions .The greatest impact of our studies will be finding of a significant viral concentration in the aerosol range (specifically, particles < 10 µm) documenting the potential for aerosol exposure to SC2. Finding substantial viral content in aerosol size fractions will have additional public health implications, as preventing person-to-person aerosol transmission is more challenging than preventing transmission via larger droplets, the focus of almost all current prevention recommendations.