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• Indoor environmental quality (IEQ) in low-income flats. • Occupants have an influence on air quality. • Variability in window opening routines and natural ventilation intervals. • Observed outcome was poor quality and often unhealthy indoor air. Thermal comfort and Indoor air quality (IAQ) in residential buildings with different degrees of airtightness was studied in two climates in Spain. Behaviour was compared in the areas occupied by day and by night. The IAQ of the buildings studied, erected before energy efficiency regulations were in place (1939–79) and lacking mechanical ventilation, was compared to their airtightness. The rationale for that approach was that under such circumstances air change depends on uncontrolled natural ventilation (=opening windows) and consequently on the outdoor temperature. Relative humidity was also taken into consideration, given the condensation that may be induced where ventilation is insufficient. In winter in both climates, the CO 2 levels were over 1200 ppm, with means on the order of 1900 ppm in Madrid and 1400 ppm in Seville and higher at night than during the day. Infiltration-mediated air changes/hour appeared to be insufficient to maintain the house under healthy conditions and the risk of surface condensation is higher in the most airtight dwellings. [ABSTRACT FROM AUTHOR]

It is generally assumed that vertical pollutant dispersion can reduce exposures to ambient pollutants in tall buildings, as concentrations of some ground-source pollutants are diluted at higher floors. However, we are aware of very few measurements of airborne pollutant concentrations that have been made specifically along the height of tall buildings. Therefore, we conducted a pilot study to measure the vertical variation in the concentrations of several outdoor pollutants and environmental parameters along the height of a ∼60-story (∼300 m) building in downtown Chicago, IL during a one-week period in the summer of 2017. Simultaneous measurements of concentrations of size-resolved particulate matter 0.3–10 μm (which were also used to estimate PM 1 , PM 2.5 , and PM 10 mass concentrations), ozone (O 3 ), nitrogen dioxide (NO 2 ), carbon dioxide (CO 2 ), and carbon monoxide (CO), as well as temperature and relative humidity, were made using multiple sets of instrumentation installed in the outdoor air intakes of the mechanical systems upstream of any filtration or mixing processes on the 2nd, 16th, 29th, and 44th floors and in an open-air area on the 61st floor. The average PM 1 and PM 2.5 concentrations estimated on the top two floors were more than 30% lower than on the 2nd floor. Temperature, humidity ratio, and CO 2 concentrations decreased with height, O 3 concentrations increased with height, and NO 2 concentrations were less consistent. Most of the differences between floors were statistically significant. Floor height was more strongly correlated with PM 1 , PM 2.5 , PM 10 , CO 2 , and O 3 concentrations than with local wind speed and direction. [ABSTRACT FROM AUTHOR]

There is a long-standing dispute about indoor air humidity and perceived indoor air quality (IAQ) and associated health effects. Complaints about sensory irritation in eyes and upper airways are generally among top-two symptoms together with the perception "dry air" in office environments. This calls for an integrated analysis of indoor air humidity and eye and airway health effects. This overview has reviewed the literature about the effects of extended exposure to low humidity on perceived IAQ, sensory irritation symptoms in eyes and airways, work performance, sleep quality, virus survival, and voice disruption. Elevation of the indoor air humidity may positively impact perceived IAQ, eye symptomatology, and possibly work performance in the office environment; however, mice inhalation studies do not show exacerbation of sensory irritation in the airways by low humidity. Elevated humidified indoor air appears to reduce nasal symptoms in patients suffering from obstructive apnea syndrome, while no clear improvement on voice production has been identified, except for those with vocal fatigue. Both low and high RH, and perhaps even better absolute humidity (water vapor), favors transmission and survival of influenza virus in many studies, but the relationship between temperature, humidity, and the virus and aerosol dynamics is complex, which in the end depends on the individual virus type and its physical/chemical properties. Dry and humid air perception continues to be reported in offices and in residential areas, despite the IAQ parameter "dry air" (or "wet/humid air") is semantically misleading, because a sensory organ for humidity is non-existing in humans. This IAQ parameter appears to reflect different perceptions among other odor, dustiness, and possibly exacerbated by desiccation effect of low air humidity. It is salient to distinguish between indoor air humidity (relative or absolute) near the breathing and ocular zone and phenomena caused by moisture-damage of the building construction and emissions therefrom. Further, residential versus public environments should be considered as separate entities with different characteristics and demands of humidity. Research is needed about particle, bacteria and virus dynamics indoors for improvement of quality of life and with more focus on the impact of absolute humidity. "Dry (or wet) air" should be redefined to become a meaningful IAQ descriptor. [ABSTRACT FROM AUTHOR]

Air pollution surveys of formaldehyde (HCHO) were conducted in 2324 rooms decorated within one year in 2007-2009 in Hangzhou, China. The mean HCHO concentration (CHCHO) was 0.107 ± 0.095 mg/m³ and 38.9% of samples exceeded the Chinese National Standard GB 50325-2010. Over the past 3 years, the CHCHO decreased with time (p < 0.05). Relationships of potential factors to indoor CHCHO were also evaluated. CHCHO was related to temperature (T), relative humidity (RH), time duration of the windows and doors being closed before sampling (DC), time duration from the end of decoration to sampling (DR) and source characteristics (d). A model to relate indoor CHCHO to these five factors (T, RH, DC, DR, d) was established based on 298 samples (R² = 0.87). Various factors contributed to CHCHO in the following order: T, 43.7%; d, 31.0%; DC, 10.2%; DR, 8.0%; RH, 7.0%; specifically, meteorological conditions (i.e., RH plus T) accounted for 50.7%. The coefficient of T and RH, R-m, was proposed to describe their combined influence on HCHO emission, which also had a linear relationship (R² = 0.9387) with HCHO release in a simulation chamber test. In addition, experiments confirm that it is a synergistic action as 7 and RH accelerate the release of HCHO, and that is a significant factor influencing indoor HCHO pollution. These achievements could lead to reference values of measures for the efficient reduction of indoor HCHO pollution. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a practical investigation into the indoor air quality of a fully air-conditioned eight-storey healthcare facility in the East Malaysia region before and after vapour decontamination. East Malaysia is located in a hot and humid climate, which favours the growth of bacteria, yeasts and moulds. The main purpose of the investigation is to identify the potential of tea tree oil vapour decontamination to improve the indoor air quality by reducing the active bacteria, yeast and mould concentrations in indoor air. A total of 336 samples have been taken inside the building for indoor air at 84 different locations and 24 samples have been taken for outdoor air at 12 locations, which are near the fresh air intakes of the air handling units. The vapour decontamination method is used in the present study. Results show that the humidity levels remain high during the entire study period, exceeding 60% relative humidity, favouring the growth of bacteria, yeasts and moulds. By applying vapour decontamination from the air handling units to the ventilated air serving areas, the average bacteria, yeast and mould count is successfully reduced to below the recommended threshold of 500 CFU m−3 for normal zones, and 35 CFU m−3 for critical zones. The decontamination study result strongly suggests that the very real potential for applying tea tree oil vapour as air treatment in tropical countries like Malaysia for indoor air quality management in healthcare facilities. [Copyright &y& Elsevier]

Abstract: A study was undertaken to determine the effect of variations in temperature, relative humidity, occupancy density and location (indoor/outdoor) on the concentrations of viable airborne bacterial and fungal spores at an air-conditioned and a non air-conditioned food stall in Singapore. Typically, bioaerosols consisted of 50.5% bacteria and 49.5% fungi in the indoor environment. In contrast, for the outdoor environment, bacteria on an average only accounted for 20.6% of culturable airborne microorganisms whereas fungal concentrations were 79.4%. Results on bioaerosol size distributions revealed that 67% of indoor bacteria and 68% of outdoor bacteria, 85% of indoor fungi and 68% of outdoor fungi were associated with fine mode particulates (<3.3 μm). Occupant density was the key factor that affected indoor airborne bacteria concentrations while concentrations of outdoor airborne bacteria depended strongly on ambient temperature. Indoor fungal concentration was positively correlated to relative humidity whereas outdoor fungal concentration was positively correlated to relative humidity and negatively correlated to temperature. The study also compared the biological air quality between a non air-conditioned food stall (Stall A) and an air-conditioned food stall (Stall B). The dining area of the former had lower bacterial concentrations as compared to the latter, while fungal spore’s concentrations showed a reverse trend. The dominant airborne bacteria genera were Staphylococcus, Pseudomonas, Alcaligens, and Corynebacterium whereas Penicillium, Aspergillus and Cladosporium were the most common fungal genera and groups in both food stalls. [Copyright &y& Elsevier]

Abstract: Research into dynamic moisture storage in hygroscopic building materials has renewed interest in the moisture buffering capacity of building materials and shown the potential for these materials to improve indoor humidity, thermal comfort and indoor air quality in buildings. This paper complements previous research by estimating the effect of hygroscopic materials on energy consumptions in buildings. The results show that it may be possible to reduce heating and cooling energy consumption by up to 5% and 30%, respectively, when applying hygroscopic materials with well-controlled HVAC systems. The paper also describes two different experimental facilities that can be used to measure accurately the moisture buffering capacity of hygroscopic building materials. These facilities provide different convective transfer coefficients between the hygroscopic material and ambient air, ranging from natural convection in small, sealed jars to fully developed laminar and turbulent forced convection. The paper presents a numerical model and property data for spruce plywood which will be used in a companion paper [O.F. Osanyintola, P. Talukdar, C.J. Simonson, Effect of initial conditions, boundary conditions and thickness on the moisture buffering capacity of spruce plywood, Energy and Buildings (2006), doi:10.1016/j.enbuild.2006.03.024.] to provide additional insight into the design of an experiment to measure the moisture buffering capacity of hygroscopic materials. [Copyright &y& Elsevier]

Data from a nationwide survey on the status of the Swedish residential building stock and indoor air quality was placed in the public domain by the National Board of Housing, Building and Planning of Sweden. The current research investigates the indoor humidity conditions in Swedish residential buildings, single-family houses and apartments, assessing the measurements from the extensive BETSI-survey against adjusted relative humidity levels based on existing norms and Standards. The aim of this study is to investigate associations and correlations between relative humidity levels and multiple building and system characteristics, occupancy patterns and behaviors and health symptoms-complaints. The analysis uses 13 categorical and 9 continuous variables-parameters of the examined dwellings. Analysis shows that low indoor relative humidity is a realistic issue in Swedish dwellings during the heating season. The issue is more prevalent in apartments than single-family houses. In addition, low indoor relative humidity seems to be more extensive in dwellings with higher indoor temperature, smaller volume, higher ventilation rate and frequent airing practices, lower number of occupants, constructed mainly after 1985, in city suburbs and in the northern parts of the country. The developed multinomial logistic regression model may predict very accurately the relative humidity level of the Swedish dwellings, during heating season. This analysis offers additional evidence to the scientific literature for possible correlation of low relative humidity with specific health symptoms, complaints and disturbances. • Low relative humidity is a realistic issue in Swedish dwellings, mainly apartments. • The issue is more extensive in dwellings with higher indoor temperatures. • Moisture supply values are suggested for this climate and dwellings. • Possible correlation of low relative humidity with specific health symptoms. • Method may be used widely also in epidemiological and health related campaigns. [ABSTRACT FROM AUTHOR]

In most urban environments, outdoor air pollutants affect indoor air quality. In 2019, Seoul, South Korea mandated filtered ventilation systems in newly constructed buildings to reduce PM 2.5 levels. This study aimed to evaluate PM 2.5 concentrations before and after the installation of a pre-filter and to analyze their behavior under different relative humidity conditions. The pre-filter system was installed in two selected houses (A and B) with the same ventilation system to evaluate indoor and outdoor PM 2.5 concentrations. To reduce indoor PM 2.5 concentrations through the ventilation system, a high-performance filtering system (G4 + F8 + H13) was installed. The ventilation system was better at maintaining indoor air quality than an air cleaner. Furthermore, the pre-filter was more effective in reducing PM 2.5 that was introduced from the outside rather than that generated indoors. The results revealed that after installation of the pre-filter system, the percentage of PM 2.5 concentration below 10 μg/m3 increased for house A and B, respectively. In addition, when the pre-filter was not installed, the average I/O ratio was 1.4 ± 0.09 and 2.3 ± 0.09 for house A and B, respectively. However, after the pre-filter was installed, the average I/O ratio for house A was 0.4 ± 0.58 and that for house B was 2.1 ± 0.05. After pre-filter installation, the percentage of I/O ratio (range of 0–1) increased with an increase in the relative humidity, that is from 72.1% to 95.1% for house A and from 8.5% to 24.7% for house B. Image 1 • Pre-filter installation prevents PM 2.5 inflow from outdoors to indoors. • After pre-filter installation, PM 2.5 below 10 μg/m3 increased. • Ventilation system was better at maintaining IAQ than an air cleaner. • I/O ratio <1 increased with an increase in relative humidity. • Increase in relative humidity is associated with a decrease in the I/O ratio. [ABSTRACT FROM AUTHOR]

• Thermal comfort and energy saving potential of DOAS-CF was studied. • Thermal comfort and IAQ acceptability were highest satisfaction at 27°C at 0.94 m/s. • Mean thermal sensation was highly correlated to the average SET* as a linear function. • Annual energy consumption of DOAS-CF was reduced by 25.8% as temperature rose 3°C. The performance of a Dedicated Outdoor Air System integrated with ceiling fans (DOAS-CF) to enhance thermal comfort, perceived air quality (PAQ) and energy-saving potential was examined. 26 subjects were exposed to the combinations of temperatures (24, 27 and 30°C) and air velocities in the range of 0.07 to 1.87 m/s at relative humidity (RH) of 60% for 3.5 h. The results showed that subjects felt thermally neutral and comfortable at 24°C with air velocity of 0.07 m/s, 27°C with air velocity of 0.94 m/s and 30°C with air velocity of 1.87 m/s. Thermal comfort (87%), thermal preference (72%), thermal acceptability (100%) and indoor air quality acceptability (98%) were highest at 27°C at 0.94 m/s. The mean thermal sensation was highly correlated to the average SET* as a linear function. An energy simulation tool (IES-VE) was used to simulate the energy consumption and quantify the energy savings of the DOAS-CF. Relative to a typical room design condition of 24°C with a conventional air-conditioning system, DOAS-CF achieved a 25.8% reduction in annual energy consumption when the room temperature was raised by 3°C but compensated by increased air movement. [ABSTRACT FROM AUTHOR]