Global evidence and research gaps on indoor air quality in healthcare facilities

Indoor air quality (IAQ) is a critical determinant of clinical safety and infection control in healthcare facilities, where vulnerable populations exhibit greater susceptibility to indoor environmental conditions. This review synthesises global evidence from 215 peer-reviewed publications identified through PRISMA screening between 2015 and 2025, comprising 26 review papers and 189 primary studies. Evaluating publication trends, setting distribution, monitored parameters and regulatory frameworks, the findings reveal a sharp post-pandemic surge in research that is heavily skewed toward operating rooms (44%) and intensive care units (35%), while high-density patient waiting areas (< 2%) remain severely understudied. Although microbial contaminants and particulate matter are consistently prioritised to track infection risks, critical ventilation performance indicators like carbon dioxide concentrations (15%) and airflow (6%) are rarely monitored. Furthermore, using Malaysia as a representative case study with year-round tropical climates highlight a significant regulatory gap, as Malaysia relies primarily on general IAQ guidelines rather than comprehensive healthcare-specific IAQ threshold standards. Findings suggested that international IAQ thresholds may not be directly transferable to tropical healthcare facilities without adaptation. By connecting global evidence with local practices, this review identified key research gaps and highlighted the need for region-specific IAQ frameworks to support patient safety, staff well-being, and infection control in tropical healthcare settings.