Quaternary ammonium compounds (QACs) are commonly used in disinfecting and personal care products for their antimicrobial, surfactant, and preservative properties. This study provides the first comprehensive assessment of QACs in assisted living facilities through the analysis of 19 QACs from three different QAC subgroups in indoor dust and air samples collected from three assisted living facilities in Indiana, United States (US), as well as in wristbands worn by the residents and staff of these facilities.