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Introduction: Airborne Biologic Particles (ABPs) are a potential risk factor for infection following total joint arthroplasty. Factors such as temperature and humidity may affect the number of ABPs which can increase the risk of infection. Comparisons of ABP count between Total Hip Arthroplasty (THA) and Total Knee Arthroplasty (TKA) have yet to be made. Our study examines the differences in ABP count between primary THA and TKA procedures. Methods: We analyzed all primary TJA procedures done within the same OR at an academic institution from April 2019 to June 2020. All procedures between the dates of March 15, 2020 – May 4, 2020 were excluded to avoid COVID-related confounding. Intraoperative measurements of temperature, humidity, and ABP count per minute were recorded. A report containing surgical data from the same time was generated using the institution’s Electronic Health Records (EHR) system and cross-referenced to the intraoperative measurements using procedure start and end times. ABP was calculated as an average ABP count per minute. Descriptive statistics were used to evaluate differences in variables of interest. P-values were calculated using t-test for continuous variables and chi square for categorical values. Results: A total of 168 cases were included in the study, comprised of 98 (58.3%) primary THA and 70 (41.7%) primary TKA. No significant differences in room temperature or particle counts across all particle sizes were found between THA and TKA groups. Similarly, time spent in the room was not significantly different between THA and TKA. The only variable that was significantly different between the two groups was average relative humidity, with higher humidity in the THA group (46.9% + 7.56 vs 44.4% + 8.02, p=0.008). Conclusion: There were no significant differences in temperature or particle count between primary THA and primary TKA procedures, suggesting OR air quality was similar between the two procedure types. Further investigation including additional variables such as OR size, airflow patterns, and different procedure types should be performed to better characterize the role of ABPs in air quality and infection risk.