OBJECTIVE: To evaluate plume composition during simulated diode laser equine upper airway surgery. METHODS: A 980-nm diode laser fiber was applied in continuous-wave mode in contact with laryngeal and pharyngeal tissues of 6 equine cadaver heads, and resultant plumes were collected for analysis. Measured parameters included the real-time concentration of particulate matter under the size of 2.5 μm (PM2.5), organic carbon (OC), elemental carbon (EC), and volatile organic compounds (VOCs). RESULTS: Visible smoke was encountered during surgical laser application and plume collection. Diode laser median activation time was 326 seconds (IQR, 116 to 387 seconds), and median energy was 8,099 J (IQR, 2,721 to 9,110 J). Mean real-time PM2.5 concentrations during laser procedures exceeded 5 mg/m3 throughout. Organic carbon concentrations were much higher than EC concentrations in the surgical plume, with a median OC/EC ratio of 422. Fifty-five individual VOCs were identified. All measured surgical plume components were higher than control samples. CONCLUSIONS: The evaluation of surgical plumes collected during simulated upper airway diode laser surgery revealed high levels of harmful fine particulate matter PM2.5 exceeding Occupational Safety and Health Administration standards. Increased OC and OC/EC ratio were also observed. Surgical plumes contained VOCs, including the known carcinogenic compounds benzene and toluene. CLINICAL RELEVANCE: These data suggest the need for mitigation strategies, such as specialized masks or local exhaust ventilation, to decrease the exposure of personnel to plumes generated during equine upper airway laser surgery.