Indoor air pollution, particularly from cigarette smoke, poses significant environmental health risks, including respiratory and cardiovascular effects. Sansevieria trifasciata has been reported as a natural air purifier capable of reducing volatile organic compounds and carbon monoxide (CO) in indoor environments. However, evidence regarding the effectiveness of plant-derived extracts combined with essential oils remains limited. Objective: To evaluate the effectiveness of Sansevieria trifasciata leaf extract, alone or in combination with essential oil, in reducing CO concentrations in enclosed indoor spaces exposed to cigarette smoke. Methods A quasi-experimental pre-test–post-test control group design was employed using four experimental rooms. Interventions included 60 mL S. trifasciata extract (PBL-21), 60 mL extract + 5 drops essential oil (PBL-20), 5 drops essential oil only (PBL-19), and control with no intervention (PBL-18). CO concentrations were measured before and after a 60-minute diffusion period using a portable CO analyzer. Data were analyzed using paired t-tests and ANOVA. Results: CO levels decreased by 37.5% in PBL-21, 68.8% in PBL-20, and 33.3% in PBL-19, while the control group showed minimal change. The combination of extract and essential oil demonstrated the greatest reduction, suggesting a synergistic effect. Conclusion: The combination of Sansevieria trifasciata extract and essential oil effectively reduced indoor CO levels from cigarette smoke in a quasi-experimental setting. These findings support the potential of plant- and essential oil-based interventions as eco-friendly, accessible strategies for improving indoor air quality. Further research with larger experimental designs and chemical profiling is recommended to validate and optimize these interventions.