Development of a Qualitative Questionnaire for Indoor Air Quality Monitoring: A Scoping Review of Subjective Assessments in Studies Using Low-Cost Sensors

Background: Individuals spend most of their time indoors, yet the influence of indoor environmental characteristics on cognitive, emotional, and physical health is often underestimated. Indoor Air Quality (IAQ) plays a critical role in preventing discomfort and health issues such as Sick Building Syndrome (SBS). This study proposes a methodological framework integrating quantitative data from low-cost sensors with qualitative assessments of user perception, enabling a comprehensive evaluation of IAQ and its impacts. Methods: To develop a qualitative questionnaire, a Scoping Review was conducted with Scopus, since the aim was to identify questionnaire components from previous studies rather than to synthesize intervention effects, as in a systematic review. Keywords related to IAQ, user perception, wellbeing, and pollutant monitoring in living and working environments were applied. Starting from 281 initial documents, only 35 were selected because they reported relevant surveys or questionnaires within the scope of the analysis. Results: Across the 35 included studies on living and working spaces, the most frequently reported questionnaire items were grouped into five thematic domains—demographic factors, health symptoms, user perceptions, building and occupancy conditions, and monitored pollutants—to support the development of the qualitative questionnaire. These five domains supported the development of the proposed qualitative questionnaire but are also readily scalable to living spaces. Conclusions: Based on these findings, a team designed a structured questionnaire covering lifestyle, demographics, workplace conditions, perceived air quality, and related symptoms. This tool supports parallel analyses of qualitative and quantitative data. The proposed framework fosters multidimensional interpretation and may inform design, management, and AI-driven approaches for improving IAQ assessment across diverse contexts.