Good Indoor Air Quality Research Articles

Indoor environmental quality in offices and risk of health and productivity complaints at work: A literature review

Many service jobs are carried out in modern offices, with individual offices being increasingly replaced by open-plan settings. The high number of adult people working in office buildings, in most situations sharing the workplace with many others during a considerable part of their daily time, highlights the importance of providing adequate guidance to ensure the quality of office environments. This paper aims to summarize existing data on modern offices' indoor environmental quality (IEQ) conditions in terms of air pollution (volatile organic compounds (VOC), particulate matter and inorganic pollutants), thermal comfort, lighting and acoustics and the respective associations with health and productivity-related outcomes in workers. Evidence shows that although many offices present acceptable IEQ, some office settings can have levels of air pollutants, hygrothermal conditions/thermal comfort and illuminance that do not comply with the existing international standards and recommendations. In addition, findings suggest the existence of significant associations between the assessed IEQ indicators and the risk of detrimental effects on health and productivity of office workers. In particular, airborne particles, CO2, O3 and thermal comfort were linked with the prevalence of sick building syndrome symptoms. Poor lighting and acoustical quality have also been associated with malaise and physiological stress among office workers. Similarly, better productivity levels have been registered for good indoor air quality conditions, in terms of VOC, airborne particles and CO2. Overall, the evidence revised in this work suggests that for promoting health and productivity recommendations for office building managers include actions to ensure that: i) all relevant IEQ indicators are periodically controlled to ensure that levels comply with recommended limit values; ii) declared indoor pollution sources are avoided; iii) adequate ventilation and acclimatization strategies are implemented; and iv) there is the possibility of conduct personalized adjustments to environmental conditions (following workers' preferences).

Long-term analysis of indoor air quality and thermal comfort in a public school

The paper is focused on the investigation of the Indoor Air Quality (IAQ) in two classrooms from a thermal renovated school from Bucharest, related to indoor carbon dioxide (CO2), ozone (O3) concentrations or airborne particles (PM2.5), by using experimental data. The experimental campaign has been conducted over a long period (February-June 2022), allowing the study of indoor air quality under different weather data conditions. The results showed that the use of classroom ventilation is mandatory in order to reach a satisfactory degree of thermal comfort and indoor air quality and even the natural ventilation by windows opening remains a simply and useful tool to lower the indoor pollutant concentrations. However, if the target is to ensure permanent good indoor air quality in these learning spaces, a mechanical ventilation system is more adapted than the natural ventilation, due to the fact it is independent of the weather factors variation (outside temperature and wind velocity and direction).

Post Occupancy Evaluation of Indoor Air Quality in Green Rated Commercial Interiors

Good indoor air quality is crucial for the health, happiness, and satisfaction of the occupants. Since we spend so much time indoors, it is essential to maintain a reasonable level of indoor air quality. One of the elements contributing to the decline in indoor air quality was the interior materials. Having acknowledged this, green building rating systems have incorporated the use of low-emitting materials as a credit that may be gained. A system for assessing commercial interiors with a focus on interior materials exists and has been used by several commercial offices. This study aimed to understand the indoor air quality in green-rated commercial interior spaces that have won points for the use of low-emitting materials and indoor air quality. A post-occupancy review was conducted on an IGBC rated green commercial interior office space, in which various pollutant concentrations were measured and observations were made regarding space usage, cleaning processes, and maintenance. Almost 41.9% of the areas that were studied had CO2 values that exceeded the threshold. Additionally, the concentration of PM 2.5 was elevated in all locations, particularly during partial occupancy. The findings indicate that the use of low-emitting materials and finishes in office interiors helped to reduce the concentration of pollutants in the indoor environment. However, the concentrations of these various pollutants also depended on several other factors, such as the ventilation system, the use of electronic equipment, the frequency of cleaning practises, etc.

Assessing the “sufficient ventilation” requirement for Austrian buildings: development of a Monte Carlo based spreadsheet calculation to estimate airing intervals and mould risk in window ventilated buildings

In Austria the lack of guidelines or standards has caused many discussions and disputes on the question if “sufficient ventilation” can be ensured with window airing only, in particular in newly constructed, airtight residential buildings. This work presents the development of a calculation method aiming to provide a simple-to-use tool to estimate the risk of mould growth and the window airing interval required to ensure good indoor air quality assuming a range of different boundary conditions and occupant behaviours. The method implements a Monte Carlo approach calculating 1000 single zone mass balances for carbon dioxide (on a room level) and water vapor (on a housing level). Air infiltration through the building envelope is accounted using the so-called LBL-model. The time interval between window airing required to comply with CO2 limit value is estimated by calculating the time evolution of the CO2 concentration for 1000 different parameter combinations. The mould risk is estimated by a 1000-fold calculation of the daily averaged indoor air humidity and the resulting water activity on critical wall surfaces. The results are displayed as probability distributions providing information on the risk that the queried situation can or cannot ensure “sufficient ventilation”. Exemplary calculations for bedrooms of new multifamily buildings estimate that intervals between window airing events (to keep time-averaged CO2-concentration below 1000 ppm), will vary between 23 and 190 minutes (representing the 5th and the 95th percentile). This is clearly below an acceptable intervention interval for bedrooms. For living rooms, the assessment shows a strong sensitivity on the “accessible” air volume. The humidity assessment for this type of housing suggests that mould growth could occur in about 17% of the cases even though air exchange corresponding to two airing events per day were assumed. An additional outdoor air exchange of up to 40 m³/h would be required to reduce the mould risk fraction to <1%, suggesting the need for mechanical ventilation concepts in residential housing to enable healthy indoor environment independently of occupant behaviour.

Indoor Air Quality and Smoking Control in Healthcare Environments in Northern China

Background: Air pollution has adverse effects on human health, while people experience regular contact with air pollutants in a high concentration via inhalation and ingestion. Nowadays, the average person spends more than 90% of their lifetime inside both private and public buildings, and this figure can reach close to 100% for the sick or elderly who cannot take care of themselves. Attention should be paid to indoor air quality (IAQ), especially for certain groups in specific places. Purpose: This study intends to investigate indoor air quality in a large general hospital in Northern China, where people desire clean air for good nursing, and then propose solutions to any air pollution present. Methods: Some influential factors related to air pollution, including PM2.5 and PM10, were measured in winter. Observations were applied to indicate that the smoking behaviors of medical staff were an important contributor to air pollution. Experimental measurements were designed to test the concentration of airborne nicotine. Questionnaire surveys and follow-up interviews were conducted to understand attitudes towards smoking behaviors and offer design strategies. Results: The scopes of 24 h mean concentrations of PM2.5 (10.2~57.8 µg/m3, 17.5~45.5 µg/m3, and 20.5~91.1 µg/m3) and PM10 (17.7~81.8 µg/m3, 13.0~83.8 µg/m3, and 31.7~188.1 µg/m3) exceeded relevant guideline values, and the airborne nicotine concentrations (1.29 µg/m3 and 1.62 µg/m3) confirmed that smoking behaviors occurred in the consulting room. Conclusions: To control tobacco to ensure good indoor air quality, smoking behaviors should be managed instead of forbidden. This will also provide greater satisfaction to medical staff. Smoking behavior management requires a comprehensive consideration based on ambient conditions and psychological demands. As there is a lack of specific requirements in relevant design regulations that are tailored to ensure the environmental satisfaction of medical staff, the findings from this study can be used as evidence to inform the design of healthcare environments for public health in future.

The Influence of Ventilation Measures on the Airborne Risk of Infection in Schools: A Scoping Review.

To review the risk of airborne infections in schools and evaluate the effect of intervention measures reported in field studies. Schools are part of a country's critical infrastructure. Good infection prevention measures are essential for reducing the risk of infection in schools as much as possible, since these are places where many individuals spend a great deal of time together every weekday in a small area where airborne pathogens can spread quickly. Appropriate ventilation can reduce the indoor concentration of airborne pathogens and reduce the risk of infection. A systematic search of the literature was conducted in the databases Embase, MEDLINE, and ScienceDirect using keywords such as school, classroom, ventilation, carbon dioxide (CO2) concentration, SARS-CoV-2, and airborne transmission. The primary endpoint of the studies selected was the risk of airborne infection or CO2 concentration as a surrogate parameter. Studies were grouped according to the study type. We identified 30 studies that met the inclusion criteria, six of them intervention studies. When specific ventilation strategies were lacking in schools being investigated, CO2 concentrations were often above the recommended maximum values. Improving ventilation lowered the CO2 concentration, resulting in a lower risk of airborne infections. The ventilation in many schools is not adequate to guarantee good indoor air quality. Ventilation is an important measure for reducing the risk of airborne infections in schools. The most important effect is to reduce the time of residence of pathogens in the classrooms.

Noise from ventilation systems in dwellings - Regulations and field test procedures in selected countries in Europe

In most countries in Europe, regulatory noise limits apply for service equipment in housing. During the last few decades, mechanical ventilation with heat recovery (MVHR) has become increasingly prevalent in new and retrofitted housing in Europe. The MVHR systems supply fresh air to obtain good indoor air quality, with minimal heat losses. However, the systems may operate continuously 24 hours/day and transmit noise into and between rooms by many possible paths. In practice, many people get annoyed or disturbed by the noise, especially during nighttime or when having quiet activities. Some countries have lower service equipment noise limits for continuous sources than for non-continuous sources, and lower limits also apply for the upper quality classes in acoustic classification schemes. Thus, both design and measurements become challenging. The aim of this paper is to investigate the noise limit values and descriptors applied to ventilation systems in housing in selected countries in Europe and compare limit values, field test and rating procedures as well as operating conditions and enforcement related to the limit values. Indications of typical design methods will also be included.

Experimental study of air distribution and heating performances of deflection ventilation

Deflection ventilation uses a purposely-designed deflector to divert supply air jet into the occupied zone directly. A few numerical studies have shown good indoor air quality with deflection ventilation. However, there was a lack of research on thermal comfort, which is also important to ensure human wellbeing. This study conducted experimental measurements when deflection ventilation was operated for winter heating. Eleven cases with different supply air velocities, supply air temperatures and deflection angles were carried out in an office-layout experimental chamber. As a comparison, another case with mixing ventilation was also measured. The predicted mean vote (PMV), draft rate (DR), air diffusion performance index (ADPI) and energy utilization coefficient (EUC) were adopted to evaluate the heating performances. The results showed that the deflection angle played a decisive role on air distribution. An inclined deflector (deflection angle: 35° downward) could elevate air temperature in the lower occupied zone as compared with a horizontal deflector (deflection angle: 0°), which provided efficient air distribution for winter heating. The average PMV values were in the range of −0.7 – 0.5, and the values of DR and ADPI in the occupied zone were typically less than 20% and higher than 80%, respectively. According to ISO 7730 and ASHRAE 113, deflection ventilation achieved satisfactory indoor environment with regard to thermal comfort. The EUC was typically greater than unity, indicating high energy efficiency of deflection ventilation, especially for the cases with deflection angle of 35°. In comparison with mixing ventilation, deflection ventilation can provide better thermal comfort as well as energy efficiency.

Monitoring summertime indoor overheating and pollutant risks and natural ventilation patterns of seniors in public housing

Indoor heat and air pollution pose concurrent threats to human health and wellbeing, and their effects are more pronounced for vulnerable individuals. This study investigates exposures to summertime indoor overheating and airborne particulate matter (PM2.5) experienced by low-income seniors and explores the potential of natural ventilation on maintaining good indoor thermal conditions and air quality (IAQ). Environmental and behavioural monitoring and a series of interviews were conducted during summer 2017 in 24 senior apartments on three public housing sites in NJ, USA (1930s’ low-rise, 1960s’ high-rise and LEED-certified 2010s’ mid-rise). All sites had high exposures to overheating and PM2.5 concentrations during heat waves and on regular summer days, but with substantial between-site and between-apartment variability. Overheating was higher in the 30s’ low-rise site, while pollutant levels were higher in the 60s’ high-rise. Mixed linear models indicated a thermal and air quality trade-off with window opening (WO), especially in some ‘smoking’ units from the older sites, but also improved both thermal and PM2.5 concentration conditions in 20% of the apartments. Findings suggest that with warmer future summers, greater focus is needed on the interdependencies among (1) thermal and IAQ outcomes and (2) technological and behavioural dimensions of efforts to improve comfort for vulnerable occupants.

Connecting Air Quality Measurements and Industrial Production as a Concept of Harmonious Management

Managing a manufacturing company currently requires anticipating development scenarios, depending on unexpected changes that occur in the environment. One such change is the need to guarantee sustainable production (SP), including in the environmental aspect of indoor–outdoor air quality. In this paper, we propose the mobile monitoring of the level of outdoor air quality of enterprises, in a city, based on the parameter's values: CO2, O3, NO, H2S, PM1, PM2.5, PM4, PM10, SO2 using sensors located in the public transport therein, thanks to which it is possible to match, in real time, those outdoor spaces with the highest air pollution. Such outdoor monitoring of the results of the air quality should indicate exactly where, in a city, anything untoward is being produced. This should result in remedial action leading to ensuring good indoor and outdoor air quality. This paper also gives a real-life case study. The harmony, in managing a manufacturing company, is visible thanks to combining the data of the examination of air quality, analysing the acquired data and recommending remedial actions, before the level of air pollution becomes critical.

Skyscrapers and the city: How tall buildings interact with their users and urban environment

Tall buildings have become a prevalent typology around the world. They carry benefits for the entrepreneur (profits) and the local authority (municipal taxes), the architect and the tenants (prestige). Yet little is known about the actual needs of the building itself, the fact that its different levels are exposed to different climatic conditions, thus have different energy needs, or the contingencies involved in living high up in, or down around them. This paper presents results of ongoing research, including tall buildings’ microclimatic peculiarities with height and ensuant energy needs; building envelope design and energy efficiency; microclimatic peculiarities created on the pedestrian level; and environmental quality. Specific modules results have been published in several papers, while additional work is ongoing, since this building prototype and its implications are still mostly poorly understood. Such work ties into climate change and the built environment, public health, survivability and resilience under extreme environmental events, which seem to become the norm. Results of parts of this research certainly tie into Covid-related contingencies and the need for usable public open spaces, efficient building ventilation to ensure good Indoor Air Quality (IAQ), and a whole array of other issues.

Determination of the Interzonal Airflows in Naturally Ventilated Dwellings Based on Concentration Measurements of the Metabolic Carbon Dioxide

The role of interzonal airflows is especially pronounced in naturally ventilated buildings. In such buildings, reversed airflows in the ventilation stacks might occur as well. This affects the air exchange rate and contaminant distribution in buildings. A significant increase in carbon dioxide concentration is a characteristic phenomenon for poorly ventilated rooms. This paper demonstrates the application of metabolic carbon dioxide concentration measurements for interzonal airflow estimation in naturally ventilated buildings. The presented method is based on the continuous measurements of CO2 concentration at one point in each zone. These measurements are used to estimate airflow pattern in a multizone building by applying an inverse analysis. The developed methodology employs an iterative Levenberg-Marquardt procedure to maximise the nonlinear likelihood function. The validity of the method was verified against measurements carried out in a single naturally ventilated room. Further, the method was applied to calculate the airflow pattern in two apartments in Poland, containing 4 and 6 zones. The obtained results revealed very poor ventilation in both investigated apartments and reversed airflow in exhaust ducts. The amount of fresh air entering the rooms was insufficient to ensure good indoor air quality. The developed methodology can be effectively used as a diagnostic tool to identify the potential problems with ventilation systems.

Assessment of the Electric Demand Management Potential of Educational Buildings’ Mechanical Ventilation Systems

Demand management is expected to reduce emissions from energy systems and support the utilization of renewable energy sources. In this paper, the focus is on the viability of educational buildings’ mechanical ventilation systems’ participation in electric demand management. The results suggest that when load shedding lasts for a short duration, the ventilation machine load seems more promising than expected for electric demand management, as even 60% of its electric power could be granted to such markets. Prolonging the load-shedding duration increases the risk of the indoor carbon dioxide (CO2) concentration exceeding the limit for good indoor air quality. This paper contributes to the academic community by providing information for the assessment of the demand management potential of buildings and eventually their significance in decarbonizing the electric energy system and filling research gaps concerning the impact of implementing demand management that involves a reduction in ventilation rate.

Air Damper Effect on Temperature and Airflow Distribution in Enhancing Thermal Comfort Performance

Heating, ventilating, and air-conditioning (HVAC) technology keeps growing towards providing people with good thermal comfort and indoor air quality. Most buildings use a centralized air-conditioning system in which the air-handling configuration of variable air volume (VAV) system focuses on controlling the zone temperature. But, some of the areas in the zone facing under-actuated and over-actuated airflow lead to the distortion of thermal comfort. Some indoor areas get too cold, and some get too hot due to improper air distribution. The indoor temperature inconsistency will affect the occupants' productivity and work performance. The main focus of this research is to improve the indoor environment's thermal performance by implementing an active air damper as an air controlling device for a centralized air-conditioning system. Indirectly, this will provide the control of temperature for a specific area in the zone with a VAV system. This paper presents the simulation results on the effect of the air damper pattern and its opening parameter against the temperature and airflow distribution in enhancing the thermal comfort performance. The simulation was performed using Ansys FLUENT to analyze three types of air damper patterns: iris, butterfly and radial. The comparison of CFD simulation results shows that the iris damper pattern can provide an acceptable range of temperature of 22 ºC to 24 ºC, which is significant to the desired thermal comfort. The uniform airflow distribution across the indoor area is obtained with no back-flow form in the ducting. Besides, there is a substantial temperature increment when the opening area of inlet airflow is reduced. Therefore, it can be concluded that the iris damper pattern is the best selection for an active air damper since it can provide the best temperature and air flow distribution performance compared to the butterfly and radial air damper.

Impact of Covid-19 on Heating, Ventilation and Air - Conditioning Systems

People spend much of their lives indoors, so air quality is particularly important to their health, ability to work, and well-being. The COVID -19 pandemic has heightened people's awareness of the importance of maintaining high indoor air quality. Such an emergency has underscored the need for adequate heating, ventilation and air conditioning systems that can provide a good indoor air quality, especially ventilation systems as important players in preventing and reducing the risk of airborne infections. In this paper, we review natural and mechanical ventilation and their roles in dealing with coronavirus, focusing on key factors for healthy indoor air. Two pillars are critical for ventilation: increased air exchange rate and air filtration in ventilation systems.

Deciphering optimal mixed-mode ventilation in the tropics using reinforcement learning with explainable artificial intelligence

The application of mixed-mode ventilation (MMV) in the tropics is challenging, given its hot and humid climate. Consequently, there are limited periods when operating in natural ventilation (NV) is desirable. Furthermore, the potential to use NV diminishes at locations characterized by generally light winds. Given the complex interactions in MMV, this study aims to use reinforcement learning (RL) to identify relationships that can further reduce cooling energy use while maintaining occupant thermal comfort. The control variable variables considered include the percentage of window opening area and dynamic cooling setpoint temperature. Results show that RL can achieve a 52% reduction in cooling energy while maintaining good thermal comfort and indoor air quality compared to the existing baselines that typically involve switching between NV and air-conditioning based on outdoor conditions. We then developed an Explainable AI (XAI) framework to prompt building scientists toward new insights into MMV control in the tropics, which consists of shapley additive explanations (SHAP) and decision tree. The SHAP is able to improve the transparency of RL strategy by revealing the impact of each input on the final decision and the decision tree can extract the key control rules from RL. Using the XAI framework, this study also identified that the RL algorithm was taking advantage of the internal thermal mass to increase cooling efficiency. The extracted rules are further applied to the actual testbed, showing the feasibility of the rules extracted by XAI approach.

Numerical investigation of the thermal and ventilation performance of a combined impinging jet ventilation and passive chilled beam system

Impinging jet ventilation (IJV) systems provide high ventilation efficiency and good indoor air quality (IAQ) in the cooling mode. However, they have a limited cooling capacity. Passive chilled beam (PCB) systems are widely used in indoor environments with high cooling loads and can potentially address the limitation of low cooling capacity of IJV. In this study, the possibility of combining IJV and PCB systems is investigated using computational fluid dynamics (CFD) simulations. The effects of two main factors, namely the percentage of cooling load removed by the PCB system (η) and supply air parameters (Lm) of the IJV system, on the thermal and ventilation performance of the IJV–PCB system are examined. The results indicate that the PCB system enhances the mixing of indoor air and effectively reduces the vertical temperature gradient in the IJV room. An optimal range of η that improves the cooling capacity and maintains the high ventilation performance of IJV is determined. This range for an IJV–PCB system is 0.15 ≤ η ≤ 0.45, considering thermal comfort, IAQ, and energy saving potential. In addition, the IJV–PCB system offers a wide selection range for Lm (0.4–1.2) compared with that of the IJV, and a high ventilation efficiency and good IAQ are maintained in the room in this range.

Internet-of-Things Based Hardware-in-the-Loop Framework for Model-Predictive-Control of Smart Building Ventilation.

In this work, a Hardware-In-the-Loop (HIL) framework is introduced for the implementation and the assessment of predictive control approaches in smart buildings. The framework combines recent Internet of Things (IoT) and big data platforms together with machine-learning algorithms and MATLAB-based Model Predictive Control (MPC) programs in order to enable HIL simulations. As a case study, the MPC algorithm was deployed for control of a standalone ventilation system (VS). The objective is to maintain the indoor Carbon Dioxide (CO2) concentration at the standard comfort range while enhancing energy efficiency in the building. The proposed framework has been tested and deployed in a real-case scenario of the EEBLab test site. The MPC controller has been implemented on MATLAB/Simulink and deployed in a Raspberry Pi (RPi) hardware. Contextual data are collected using the deployed IoT/big data platform and injected into the MPC and LSTM machine learning models. Occupants’ numbers were first forecasted and then sent to the MPC to predict the optimal ventilation flow rates. The performance of the MPC control over the HIL framework has been assessed and compared to an ON/OFF strategy. Results show the usefulness of the proposed approach and its effectiveness in reducing energy consumption by approximately 16%, while maintaining good indoor air quality.

A Study on the indoor air quality (IAQ) at primary school in Industrial Area: A case study to Sekolah Kebangsaan Pasir Gudang 3(SKPG3)

Existing research has shown that numerous air contaminants are present in classrooms, sometimes in high concentrations, which may have an impact on children’s health and academic performance. In order to create a safe, healthy, productive, and comfortable atmosphere for students, instructors, and other school personnel, schools must have good indoor air quality. This study has assessed the current IAQ’s level at selected school in one of the industrial areas in Johor Bahru, which is Pasir Gudang. To measure the quality of the indoor air parameters, three chemical substances which are Formaldehyde (HCHO), Total Volatile Organic Compound (TVOC) and Particulate Matter (PM) in the classroom were assessed. Besides that, this study also analyzed the temperature and relative humidity of the classroom surrounding. Furthermore, the students’ insight on the impact of IAQ parameters towards their class performances were also explored using questionnaire survey. It was found that physical parameters of the classroom were in good state, but the relative humidity percentage range was too high. Meanwhile, on the chemical contaminants, the measurement shows that the concentration of PM, HCHO and TVOC for the classroom are still in the permissible exposure range. In the end, some suggestions have been made to provide good indoor quality in the classroom by emphasizing proper design, construction, and ongoing maintenance procedures.

Nationwide evaluation of energy and indoor air quality predictive control and impact on infection risk for cooling season.

Since the coronavirus disease 2019, the extended time indoors makes people more concerned about indoor air quality, while the increased ventilation in seeks of reducing infection probability has increased the energy usage from heating, ventilation, and air-conditioning systems. In this study, to represent the dynamics of indoor temperature and air quality, a coupled grey-box model is developed. The model is identified and validated using a data-driven approach and real-time measured data of a campus office. To manage building energy usage and indoor air quality, a model predictive control strategy is proposed and developed. The simulation study demonstrated 18.92% energy saving while maintaining good indoor air quality at the testing site. Two nationwide simulation studies assessed the overall energy saving potential and the impact on the infection probability of the proposed strategy in different climate zones. The results showed 20%–40% energy saving in general while maintaining a predetermined indoor air quality setpoint. Although the infection risk is increased due to the reduced ventilation rate, it is still less than the suggested threshold (2%) in general.Electronic Supplementary Material (ESM)The Appendix is available in the online version of this article at 10.1007/s12273-022-0936-6.