Thermal comfort in educational buildings affects not only the well-being of students but also their academic performance. Over time, various methods have been developed to assess it. However, none of them takes into account the adaptation of students of different ages, which is an important issue. In recent years, the study of thermal comfort has become very important due to energy-saving measures and ventilation protocols to combat the spread of the SARS-CoV-2 coronavirus. Therefore, it is necessary to gather all the information to guide future research. Thus, this paper presents a comprehensive review of field studies on thermal comfort in classrooms at different educational levels. The focus is on those conducted during the global pandemic of COVID-19. It has been observed that students from climates with a higher degree of variation have shown a better adaptation. Children also tended to feel less affected by changing temperatures. High school and university students showed a greater range of dissatisfaction with heat than with cold. The adaptive approach is more suitable for recognising the comfort needs of all age groups. However, by using this approach together with the Fanger method, more reliable results have been reported. In most of the studies, comfort levels were found to be lower than those indicated by the standards, highlighting the need for guidelines adapted to the thermal comfort conditions of all students. Finally, the various natural ventilation measures to avoid COVID-19 infection have led to a decrease in comfort levels, especially in winter.

Nitrous acid (HONO) is an emerging indoor pollutant that can exert adverse health effects. The chemical production of indoor HONO has been attributed to NO2 heterogeneous reactions, and the source strength has been extensively evaluated via laboratory and model simulation studies. Photolysis of surface nitrate has recently been proposed as an indoor HONO source based on correlation analysis between indoor HONO accumulation and visible light radiation. However, neither experimental validation of the proposed mechanism nor source strength characterization is currently available. In this work, we designed an outdoor photochemical chamber (OPC) to simulate indoor HONO accumulation and established an indoor photochemical model (ICM) to calculate the indoor HONO budget. Indoor HONO accumulation revealed a distinct diel variation with a daytime maximum. Only with this indoor HONO source, the ICM reproduced the indoor HONO budget determined in the OPC. The enhanced reactive cross section of surface nitrate in visible light accounted for the major portion of the HONO source budget (77.2%) and the distinct diel variation. Success with the ICM encouraged us to simulate the HONO budget in real indoor environments. The calculated HONO production rates from surface nitrate photolysis at noon ranged from 1.4 to 4.1 ppbv h-1 under different indoor scenarios. On a daily average, this indoor HONO source contributed 42.4–52.7% to the total chemical sources in the living room but only contributed 4.7% to that in the kitchen, where NO2 heterogeneous reactions dominated.

The objective of this study was to measure particulate matter (PM) total loss rates in three older (1940s, 1960s, and 1980s) elevators in California during two phases and three low-cost intervention modes. Tracer gas decay and <2 μm aerodynamic diameter nontoxic NaCl particles (PM2) were used to calculate PM2 loss rates. The NaCl particles were considered surrogates for smaller particles carrying SARS-CoV-2. Empirical PM2 loss rates were paired with modeled dynamic scenarios to estimate SARS-CoV-2-relevant PM2 removal. Mean loss rates (hr-1) ranged from 1.8 to 184. Compared to a closed-door, stationary elevator, the moving elevators had a fourfold increased mean loss rate (hr-1), while an air cleaner in a stationary elevator increased the mean loss rates sixfold. In a dynamic particle removal simulation of a ten-story elevator, PM was removed 1.38-fold faster with an air cleaner intervention during bottom and top floor stops only (express ride) and 1.12-fold faster with an air cleaner during every other floor stops. The increase in removal rates due to the air cleaner was modest due to the higher moving and open-door removal rates, except during stationary phase. The half-life of PM2 particles in a stationary elevator after all passengers have left can be 8-12 minutes following a single emission and 2-5 minutes with an air cleaner. The low particle removal rate in the stationary elevator requires an intervention so that the particle removal rate will be high to eliminate infectious aerosol. If codes permit, keeping the door open when the elevator is stationary is most effective; otherwise, an air cleaner in a stationary elevator should be used. While an air cleaner is commonly seen as a substantial improvement in reducing potential virus concentration in air, in the moving elevator scenarios, the effect is quite modest. This paper provides empirical particle loss rates inside elevators, the effectiveness of air cleaners in a dynamic elevator space, two approaches to control infectious agents while the elevator is stationary, and support for a precautionary approach towards elevator use amidst a pandemic.

Indoor radon is a well-documented environmental factor as a second cause of lung cancer. Based on the chronological data on indoor radon concentration, lung cancer incidence, and the distribution of sex-age-specific population, the risk of lung cancer caused by indoor radon exposure in a total of 15 cities in China was assessed by using the risk model developed by the U.S. Environmental Protection Agency (EPA) in this study. The estimate revealed that both the excess relative risk (ERR) and lifetime relative risk (LRR) have obviously increased after 2010. The population attributable risk (PAR) in 2016 was estimated in a range from 6.66% to 22.42%, with a median of 15.33% for the 15 cities. The lung cancer incidence attributed to indoor radon in 2016 ranged from 3.96 to 15.07 per 10,000 population in males and 1.21 to 8.27 per 10,000 population in females. Across age and sex, the risk of lung cancer caused by indoor radon was found more pronounced in males and 40-45 age groups. The chronological variation of radon concentrations was considered in this study; the estimate of lung cancer caused by indoor radon in China is considered more reasonable than ever before.

With the rapid development of the real estate industry in China, urban air quality is inevitably affected. By using data of Chinese cities located in the Yangtze River Delta from 2009 to 2018, this paper is aim at examining the casual impact of house prices on air quality. By considering the endogenous problems, in this study, first, the birth rate of the previous six years and the area of state-owned land supply per capita in the previous year are taken as instrumental variables of house price. Second, the two-stage least squares method is used to assess the causal impact of house price on air quality. The findings of this study show that there is no significant relationship between urban house prices and air quality, and these results are obtained without considering the endogenous problem. While, after considering the endogenous problem, urban house prices showed a significant negative effect on overall air quality, especially for low administrative level cities. The increase in house prices has hindered the improvement of air quality mainly through the blind-scale expansion of real estate development investments and the inhibitory effect of innovation.

Production and use of chlorophenols (CPs) are being phased out around the globe, but with considerable lag in some highly populated countries. The process could be incentivized by leading countries sharing their experiences on problems that occurred, including the built environment. We previously reported that Swedish industry and authorities promoted CPs, including pentachlorophenol (PCP), as wood preservatives in buildings for decades. Yet, Swedish indoor research did not recognize exposure to the hazardous CPs and their odor potent derivatives, the chloroanisoles (CAs), which smell like mold and still evolve from legacy preservatives in damp building structures. We hypothesized that the toxic CPs and odorous CAs could be key players for health and odor problems not only in Sweden but also in the neighboring Nordic countries. We found no reports in scientific medical literature of CPs being used in buildings in these countries. However, grey literature shows that CPs were indeed used, even during building booms, in house exteriors, constructions, and interiors, from the 1950s up to the late 1970s (Denmark) and even the 1990s (Finland and Norway). One application of CPs was in houses erected on dampness-prone house foundations, conditions ideal for formation of odorous CAs through microbial methylation. Furthermore, our searches suggest that these problematic chemicals played hitherto unrecognized key roles when indoor air research evolved. Thus, odor became an important aspect of the “sick building syndrome” in Denmark and an early warning sign of health risks in Finland, as asthma and allergy were attributed to “dampness and mold.” None of the countries addressed the possible links between odor and health effects and exposure to CAs and CPs. In conclusion, our results suggest that unrecognized indoor exposure to toxic CPs and odorous CAs has mislead Nordic indoor air research for decades.

Nicotine, the primary component of cigarette smoke, is not only addictive but also indirectly contributes to lung diseases by increasing heart rate and blood pressure upon inhalation. Therefore, managing nicotine content in cigarette smoke necessitates accurate quantitative analysis. Nicotine from cigarette smoke is collected using a Cambridge filter, subjected to solvent extraction, and analyzed using instrumental techniques. However, since nicotine is susceptible to light-induced oxidation, losses may occur during pretreatment, reducing result reliability. This study assesses nicotine loss under various lighting conditions and storage durations. Nicotine collected in Cambridge filters is exposed to dark, visible radiation, and UV radiation (254 nm) for different time intervals (0–48 h), and the nicotine content is analyzed and compared. In dark conditions, a 1.6% decline in nicotine concentration occurs after 48 h. With visible radiation, a 9% reduction is observed, while under UV exposure, the concentration decreases by 16.9%. The UV radiation-associated decrease in nicotine concentration is −0.335% h−1, exhibiting strong linearity ( R 2 = 0.9465 ). Consequently, significant nicotine loss in Cambridge filter-collected samples is influenced by storage duration and lighting conditions. This study’s findings can enhance the accuracy of nicotine quantification in cigarette smoke, thereby improving the understanding of nicotine’s harmful effects in cigarette smoke.

The COVID-19 pandemic caused a paradigm shift in our way of using heating, ventilation, and air-conditioning (HVAC) systems in buildings. In the early stages of the pandemic, it was indeed advised to reduce the reuse and thus the recirculation of indoor air to minimize the risk of contamination through inhalation of virus-laden aerosol particles emitted by humans when coughing, sneezing, speaking, or breathing. However, such recommendations are not compatible with energy saving requirements stemming from climate change and energy price increase concerns, especially in winter and summer when the fraction of outdoor air supplied to the building needs to be significantly heated or cooled down. In this experimental study, we aim at providing low-cost and low-energy solutions to modify the ventilation strategies currently used in many buildings to reduce the risk of respiratory disease transmission. Measurements of the indoor air bacterial concentration in a typical office building reveal that ultraviolet germicidal irradiation (UVGI) modules added to the HVAC system are very efficient at inactivating pathogens present in aerosols, leading to indoor concentrations as low as outdoor concentrations, even with significant indoor air recirculation. Moreover, measurements of the CO2 and aerosol air concentration reveal that, with air supply vents placed in the ceiling, placing the air exhaust vents near the floor instead of on the ceiling can improve the ventilation capacity in terms of effective flow rate, with significant consequences in terms of energy savings.

Currently, preventing epidemics is an extremely critical global topic. Using present data to quickly conduct virus simulations is a difficult but interesting problem, especially when real situations are difficult to experimentally demonstrate. In the past, most studies have used package software for disease transmission simulation, but this approach is limited by availability and software cost. Therefore, we propose a visual simulation of disease transmission using building information modeling data and a 3D model using Unity. The results show that the proposed method can effectively predict the probability and route of disease transmission; it also verifies that the vertical pipeline on the floor plane is conducive to the spread of the virus (90%), and disease transmission on the plane gradually expands outward from the starting room and has a higher probability of spreading (80%) from the opposite room. In addition, a vertical pipeline was simulated using a toilet exhaust air ventilation pipeline, from which it can be observed that the adjacent floors have a higher diffusion probability (70%). It has also been confirmed that distance is the primary factor affecting disease transmission. This framework may provide designers and managers further protection against the spread of future epidemics.

As we spend approximately 80% of our time indoors, improving indoor air quality is necessary to lessen the spread and impacts of respiratory diseases and other health issues caused by particle pollution. Currently, in many countries, the primary method of cleaning indoor air is by using better, higher-grade filters in a recirculating air system or increasing ventilation with outdoor air. One way to supplement these time-tested approaches is by implementing ionization. We used a bipolar ionizer to test the removal efficiency of filters on different particle sizes with and without ionization. Calibrated cigarettes were used to generate smoke into a 28-cubic-meter chamber with a recirculating air handling system. It was found that ionization had a 275% increase in the removal efficiency of the most penetrating particle sizes (100-500 nm). We conclude that ionization drastically improves the filter removal efficiency of fine and ultrafine particles in indoor environments.