Co-existence of normal and lognormal distributions for climate and environmental parameters in air-conditioned spaces

Abstract

<p>Indoor environments, particularly intermittently air-conditioned (AC) spaces, exhibit significant temporal heterogeneity. Most existing monitoring data reveal an approximately lognormal distribution of pollutant concentrations, and an approximately normal distribution of air temperature and humidity. However, thermal parameters and pollutant concentrations have been separately studied, in terms of their statistical distributions, in the literature. In this study, we conducted a year-long monitoring of thermal and pollutant parameters in six AC spaces with different air-conditioning systems. Using an in-house monitoring system with calibrated low-cost sensors for temperature, humidity, CO2, and particulate matter, alongside commercial sensors for occupancy and duct airflow rates, we collected a comprehensive dataset, which was analyzed herein together with additional data from building management systems and weather stations. Our findings reveal that concentrations of CO2 and particulate matter approximately follow a lognormal distribution, while air temperature and humidity approximately follow a normal distribution, across AC and non-AC hours in all seasons. Possible mechanisms for these distribution differences are discussed. The findings of this study may prove crucial for addressing extreme environments and indoor overheating to protect human health.</p>