BACKGROUND: Filtered-exhaust helmet systems are commonplace during total joint arthroplasty, but their ability to limit intraoperative contamination has been questioned. We hypothesized that activation of the airflow system after complete gowning would lead to decreased contamination of the surgical environment. METHODS: Using a fluorescent particle model, the maximal particle spread from a filtered-exhaust helmet and contamination of the surgical environment based on timing of airflow activation through simulated surgical gowning procedures were evaluated. RESULTS: Helmet airflow analysis revealed particle spread greater than 5 feet in all trials. Activation before gowning resulted in a significantly greater contamination in the control group compared with the experimental group (P = .014). CONCLUSIONS: We recommend complete surgical gowning before activation of the airflow system.