Indoor Air Research Articles

Indoor Air Quality Monitoring System with High Accuracy of Gas Classification and Concentration Prediction via Selective Mechanism Research.

The efficacy of sensors, particularly sensor arrays, lies in their selectivity. However, research on selectivity remains notably obscure and scarce. In this work, indoor pollutants (C7H8, HCHO, CH4, and NO2) were chosen as the target gas. Following the screening of six oxides from previous work, temperature-programmed desorption/reduction experiments were conducted to delve into the origins of selectivity. The results explicate the superiority of NiO in detecting toluene and unveil the distinctive NO2 sensing mechanism of WO3 sensors. Based on the sensor array comprising these oxides, it can clearly detect low concentrations of C7H8 (S = 1.6 to 50 ppb), HCHO (S = 1.4 to 50 ppb), and NO2 (S = 3.3 to 50 ppb), which satisfies the requisites of indoor air monitoring. Meanwhile, three machine learning models (Extreme Gradient Boosting, Support Vector Machine, and Back Propagation Neural Network) are employed for gas classification. The classification accuracies of these models are 95.45%, 100%, and 100%, while the R2 values of the concentration prediction are 99.65%, 94.9%, and 98.04%, respectively, indicating the rationality of material selection. Furthermore, it can still achieve relatively high accuracy in gas classification (94.12%) and concentration prediction (89.36%), even for gas mixtures of four gases. Finally, an indoor air quality monitoring system is developed, which enables real-time monitoring of indoor gas quality through the Internet of Things.

60-GHz Millimeter-Wave over Visible Light Communications for Downlink Wireless Networks

Background and Objective: In this paper, we address potential solution for downlink wireless communications by integrating visible light communications (VLC) with the broadband radio frequency (RF) networks operating at 60 GHz-millimeter wave (mmWave) band. For this hybrid design, the outdoor 60 GHz-mmWave based RF link is utilized to ensure backhaul connectivity for VLC indoor system, while the VLC exploiting the lighting infrastructure that essentially used LEDs as optical source to provide low-cost and high-speed data access. Methods: The hybrid 60 GHz-mmWave/VLC system is analyzed by using 16-QAM OFDM signal, and its performance is investigated by evaluating the signal to noise ratio (SNR) and the received signal power distributions, for regular placement of LEDs and random location of receivers within the room. The impact of the transmitter-receiver parameters, and their orientations and directivities are also considered. Results: Numerical results show the efficiency of the proposed system, which can retransmit RF signals at 60 GHz-mmWave band using visible optical carriers in the indoor environment. Conclusion: The results suggest that the hybrid 60 GHz-mmWave/VLC system is able to provide reliable wireless data transmission, making it an attractive solution for downlink indoor communications.

Systematic review of indoor soundscape assessments: Activity-based psycho-acoustics analysis

This study examines 22 peer-reviewed papers to offer insights into the current utilization of psycho-acoustic sound quality metrics in research focused on indoor soundscapes. The selection of papers followed the PRISMA method for systematic review, followed by descriptive and bibliometric analyses. The review focuses on (i) identifying what psycho-acoustic indicators can be utilized to obtain an objective soundscape assessment, and (ii) determining if soundscape descriptors vary with the desired activities within the indoor space. The findings provide an overview of how psycho-acoustic sound quality metrics are used to predict perceived annoyance in indoor environments. The discussion delves into response variables related to occupants’ sound perception across various indoor settings. It highlights the lack of sufficient research on prediction models based on psycho-acoustic sound quality metrics within indoor soundscapes. Further research is required to develop tools enabling the optimal design of indoor soundscapes, which can vary according to the intended use of the room.

A seasonal investigation of indoor air quality in relation to architectural features in government office buildings in Enugu, Nigeria

Indoor air quality (IAQ) is crucial to environmental health significantly impacting on the well-being and productivity of building occupants. Several studies have explored various aspects of IAQ in non-tropical regions but there is limited information on how seasonal variations affect IAQ in hot-humid climates like Enugu, Nigeria. This study investigated seasonal changes in key indoor air parameters including CO, CO2, HCHO, TVOC, temperature, RH, PM2.5, and AQI across rainy and dry seasons in 58 government offices in Enugu, and evaluated how these fluctuations relate to architectural features of the offices. Using a mixed-methods approach, data collection involved qualitative assessments of building design attributes alongside quantitative IAQ measurements taken with the BOSEAN T-Z01Pro detector. Seasonal variations were analyzed using paired T-tests, ANOVA, and regression models. The results revealed a marked increase in pollutant concentrations during the dry season (p < 0.001–0.005), resulting in a poorer air quality index compared to the rainy season. Architectural features accounted for 68.5% of the variability in AQI (R2 = 0.685, p = 0.000), with casement windows being significantly associated with better air quality (Exp B = -4.217, p = 0.013) These shows that the dry season poses a greater risk to IAQ which is worsened in offices where projecting windows were used, potentially impacting health and productivity. The study emphasizes the need to address seasonal IAQ differences when designing office buildings in tropical regions. Design architects can help reduce seasonal air quality challenges and support healthier, more productive indoor environments by incorporating ventilation strategies, such as the use of casement windows. Further research should include long-term monitoring across various settings and additional IAQ parameters for better understanding of IAQ dynamics.

A framework for assessing the current and future capability of mechanical night ventilation in the context of climate change

Night ventilation is a technique in which the indoor air and the building’s thermal mass is cooled down during nighttime to provide a heat sink available during the next day to help mitigating overheating and reducing the daytime space cooling demand. This paper proposes a framework on evaluating the use of mechanical night ventilation today and in the future. It considers analysis of the ventilative cooling system, including mechanical night ventilation, by means of key performance indicators that involve thermal comfort, energy use and resiliency criteria as suggested by IEA Annex 80. It, additionally, introduces an economic parameter in form of diurnal and nocturnal price ratio of electricity as economic trade-off between nighttime fan- and daytime fan and chiller use in terms of electricity. A historic office building in north-central Sweden is presented as a detailed case as to illustrate the use of the framework. The investigation was done using a validated model of the building in IDA-ICE building simulation program at both current climate and future climate in 2050s. It was revealed that an upgraded ventilative cooling system with three times larger capacity is required to fulfill thermal comfort. Even though mechanical night ventilation could result in the annual cooling source electricity saving intensity up to 0.9 kWh/(m²∙a) at extreme current climate (2018), it could just insignificantly reduce the total electricity use for space cooling (up to 2 %) and only at some night ventilation rates at all mentioned climates. Mechanical night ventilation, however, could be applied in an economically beneficial way if the electricity network has different nocturnal and diurnal electricity prices. A unitless index of maximum nighttime over daytime electricity price ratio was proposed representing the maximum tolerable price for nighttime electricity, given a daytime electricity price, based on night- and daytime ventilation electricity demand. For economically justified application of mechanical night ventilation, lower nighttime over daytime electricity price ratios were required for higher night ventilation rates. For the typical future climate with night ventilation rates larger than 2.6 ACH, it will be necessary to have nighttime prices that are lower than daytime if mechanical night ventilation is to be economical. The approach used in the framework can be applied to future research and practice, regardless of the case-specific parameters such as building type, climate zone, location, etc.

CFD simulation of indoor-outdoor wind-driven ventilation and traffic pollutant dispersion at a T-shaped street intersection (ISHVAC 2023)

Traffic exhaust is considered a predominant pollutant source for buildings along streets. However, there are few studies on ventilation and pollution dispersion inside buildings and along streets in a T-shaped intersection. This study investigates the ventilation performance and pollutant dispersion inside and outside multi-unit buildings at T-shaped intersections in different wind directions. Different wind-driven ventilation modes have been compared, i.e. SS2 (single-sided ventilation with 2 openings) and CV (cross ventilation). The results show that multi-unit buildings have the potential to enhance SS2 ventilation performance. The diffusion of outdoor pollutants into indoor environments is more closely related to wind direction for SS2 than CV. However, at certain wind directions (θ = 135°), a significant increase in indoor pollutant concentrations is observed in CV, nearly tenfold higher than that in SS2 cases. The findings could contribute to the understanding of ventilation in multi-unit buildings at T-shaped street intersections.

Assessment of Formaldehyde’s Impact on Indoor Environments and Human Health via the Integration of Satellite Tropospheric Total Columns and Outdoor Ground Sensors

Formaldehyde (HCHO) is harmful to human health and an adequate assessment of its concentrations, both in outdoor and indoor environments, is necessary in the context of sustainable policies designed to mitigate health risks. In this research, ground indoor and outdoor HCHO measurements are integrated with the analysis of tropospheric total columns obtained by satellite surveys to assess the concentrations of HCHO in a number of environments, exploiting the proximity of a World Meteorological Organization—Global Atmosphere Watch (WMO/GAW) observation site in Calabria, Southern Italy to a National Institute for Insurance against Accidents at Work (INAIL) department in the municipality of Lamezia Terme. The meteorological parameters used by the WMO station are also used to provide additional data and test new correlations. Using statistical significance tests, this study demonstrates the presence of a correlation between indoor and outdoor HCHO concentrations, thus showing that an exchange between indoor and outdoor formaldehyde does occur. Rooms located in the local INAIL building where indoor measurements took place also demonstrate degrees of susceptibility to HCHO exposure, which are correlated with the orientation of prevailing wind corridors in the area. The new findings constitute an unprecedented characterization of HCHO hazards in Calabria and provide regulators with new tools with which to mitigate formaldehyde-related risks.

Exploring the health impacts of window views: a literature review

ABSTRACT Window views are closely related to indoor environmental quality and influence health and well-being. This study aimed to review quantitative studies investigating the health effects of window views. It was conducted in four stages: literature identification, screening and selection, eligibility determination, and data synthesis and thematic analysis. Database searches yielded 5,616 articles; ultimately, 121 studies were included. The results showed the effects of different aspects of window views on various health-related outcomes, as reflected in physical, psychological, and life experience. Overall findings confirmed the important associations between window views and health. There were significant variations in the number of studies on different aspects of views. The largest number of studies was related to view content, with a larger a number of studies on nature features, and demonstrated positive outcomes in several health domains. There were fewer studies on access and clarity, and their impact on health-related outcomes needs to be further determined. Future research should consider the consistency of measurement, the complexity of pathways of influence, and the combined effects of multiple factors. This review provides useful insights for research on the health benefits of indoor environments and has potential value for evidence-based design and related guidelines and standards.

Robot Localization Method Based on Multi-Sensor Fusion in Low-Light Environment

When robots perform localization in indoor low-light environments, factors such as weak and uneven lighting can degrade image quality. This degradation results in a reduced number of feature extractions by the visual odometry front end and may even cause tracking loss, thereby impacting the algorithm’s positioning accuracy. To enhance the localization accuracy of mobile robots in indoor low-light environments, this paper proposes a visual inertial odometry method (L-MSCKF) based on the multi-state constraint Kalman filter. Addressing the challenges of low-light conditions, we integrated Inertial Measurement Unit (IMU) data with stereo vision odometry. The algorithm includes an image enhancement module and a gyroscope zero-bias correction mechanism to facilitate feature matching in stereo vision odometry. We conducted tests on the EuRoC dataset and compared our method with other similar algorithms, thereby validating the effectiveness and accuracy of L-MSCKF.

Qualitative Mechanisms of Perceived Indoor Environmental Quality on Anxiety Symptoms in University

The indoor environment is widely acknowledged as a non-pharmacological tool for regulating residents’ mental health. In dormitory environments with relatively high residential density, the mental health of university students requires particular attention. This study surveyed 445 students from a northern Chinese university and used structural equation modeling (SEM) to analyze the impact of perceived indoor environmental quality (IEQ)—including thermal, lighting, acoustics, indoor air quality, and overcrowding—on self-reported anxiety symptoms. The results indicated the following: (1) students’ perceptions of dormitory IEQ significantly affected anxiety symptoms, explaining 40% of the variance; (2) anxiety symptoms associated with the IEQ were mainly characterized by anxiety and panic (r = 0.91, p &lt; 0.001); (3) subjective perceptions of the acoustic environment (r = −0.55, p &lt; 0.001) and indoor air quality (r = −0.15, p &lt; 0.05) were key predictors of anxiety, while thermal environment, lighting environment, and overcrowding were not significant. The findings enrich the IEQ system and provide directions for optimizing the dormitory indoor environment from the perspective of student mental health, with implications for other types of residential buildings.

Innovative Antifungal Photocatalytic Paint for Improving Indoor Environment

Indoor air quality (IAQ) has emerged as a global concern due to the increasing presence of indoor pollutants, which have been shown to negatively impact public health. These pollutants stem from various household activities and the materials used in buildings. Previous studies have explored several methods to improve IAQ, including gas adsorption, ozonation, non-thermal plasma, and photocatalytic oxidation (PCO). However, these methods often have drawbacks, such as generating secondary pollutants or incurring high costs. This study examines the effectiveness of photocatalytic paint, which is activated by visible light, in controlling fungal growth to enhance IAQ. Experimental results showed that when applied to grown fungi, the photocatalytic paint led to a significant reduction in the size of fungal fibers, as observed through scanning electron microscopy (SEM). Furthermore, exposure to the photocatalytic paint reduced the size of fungal hyphae by 37% after 85 h. The paint produced by adding 1 mL photocatalytic paint to 10 mL commercial paint demonstrated high efficiency in fungi removal, i.e., reducing the weight of fungi by approximately 45% within 3 h. These results highlight the potential of photocatalytic paint to significantly inhibit fungal growth, offering a promising solution for improving indoor environments.

Indoor Airborne Microplastics: Human Health Importance and Effects of Air Filtration and Turbulence

Microplastics (MPs) are omnipresent particles that receive special attention because of their persistent nature and their potential impact on human disease and on the environment. Most MPs are generated by the degradation of larger plastic items such as clothing, car tires, and discarded plastic materials. In indoor environments, where human beings spend most of their time, aerial MP levels are higher, and the majority are fibers produced from textiles. Airborne MPs indoors are a greater potential danger to humans than MPs ingested in food and drink. Fragments small enough to remain substantially suspended in the air column, the small airborne microparticles that are measured as PM10 and PM2.5, become available for assimilation by human beings through respiration, potentially producing various health problems. Larger MPs act by ingestion and skin contact. MPs can carry microorganisms and micropollutants adsorbed to their surfaces, facilitating their uptake and survival within the human body. Indoor airborne MPs thus represent emerging pollutants of fast-growing concern that are especially important as potential invaders of the human respiratory system, reaching the alveoli of the lungs and finally entering the circulatory system and other tissues. Since this direct human exposure to MP contamination via indoor air is so important, we discuss in this article the ways in which MP concentration and dispersal in indoor air can be affected by air turbulence that is induced by anthropogenic objects such as air conditioners, filters, and purifiers. Much evidence is equivocal and further research is necessary.

Advancing characterization of VOC diffusion in indoor fabrics: A dual-porosity modeling approach

Volatile organic compounds (VOCs) are major chemical pollutants in indoor air. Indoor fabrics, such as curtains, carpets, sofas, and clothes, strongly adsorb VOCs due to their high loading rates and large specific surface areas. The desorption of VOCs from these fabrics can act as a secondary source, worsening indoor air pollution and prolonging its effects. The diffusion coefficient is a key parameter that determines the source-sink properties of fabrics. In this study, the VOC diffusion characteristics in fabrics were investigated through microstructural examination, mass transfer analysis, and environmental chamber experiments. Yarn and fiber gaps were identified as dual mass transfer channels within the fabrics and were represented using two distinct fractal models. A dual-porosity medium (DPM) model, based on these fractal representations, was developed to predict the VOC diffusion coefficients in indoor fabrics and was validated via experiments under various environmental conditions and fabric-VOC combinations. The results highlight the significant impact of fabric structure and composition on VOC adsorption and emission dynamics. The validated DPM model provides a comprehensive approach to predicting VOC diffusion in fabrics, providing a more accurate method for assessing indoor air quality and fabric-mediated human exposure.

Summer Energy Use and Comfort Analysis in Rural Chinese Dwellings: A Case Study of Low-Income Older Populations in Shandong

This paper aims to investigate the indoor environmental conditions and energy use behaviours of older individuals in rural cold climates of China, with a specific focus on cooling practices during the summer months in the Shandong region. This study employs a mixed-method approach, combining quantitative indoor environmental monitoring with qualitative interviews and observations, to explore the relationship between environmental factors, household living conditions, and energy use patterns across five types of elderly households: three generations living together, older people living with grandchildren, older people living with children, older couples living together, and older people living alone. Data collection was conducted over five weeks during the summer of 2023 using HOBO UX100-003 data loggers, while external weather conditions were monitored by the China Meteorological Administration. Face-to-face interviews were conducted to gain deeper insights into daily cooling behaviours and energy use. The results reveal that cooling practices and indoor environmental conditions vary significantly among the different household types. Multigenerational households showed more complex energy use dynamics, with younger family members frequently operating high-energy appliances like air conditioners, while older individuals tended to rely on natural ventilation and electric fans to reduce energy costs. In contrast, older couples and solitary older individuals demonstrated more conservative cooling behaviours, often enduring higher indoor temperatures due to limited financial resources and a desire to minimize energy expenditures. Despite the high energy use intensity in some households, many homes failed to achieve comfortable indoor environments, particularly in dwellings with minimal insulation and older building materials. This study concludes that economic status, household structure, and building characteristics play crucial roles in shaping cooling behaviours and indoor comfort during the summer.

Contact Risk Assessment in Dynamic Indoor Settings through Agent‐Based Modeling: A Spatially Explicit and Reproducible Approach

This study introduces an agent‐based model (ABM) pedestrian simulation tool to assess the risk of close contact (6 feet) in dynamic indoor environments, specifically in urban settings with diverse social activities and spatial structures. Our approach uses machine learning‐based sensitivity analysis (SA) to identify factors impacting the number of individual contacts, such as individual stay time and area. In addition, we conducted an in‐depth quantitative analysis to evaluate how specific factors, such as the strategic placement of obstacles, dwell time, and stay time near the entrances, mitigate the number of contacts. This analysis provides valuable insights for developing practical guidelines to curb contact risks in indoor environments. Lastly, we share the model, validation methods, and associated data as an open‐source Python library, complete with comprehensive documentation. This aims at fostering collaborative research and enables the application of our model across various scenarios, contributing to the development of spatially explicit models. Such efforts enhance the understanding of contact risks in urban indoor settings and promote joint research efforts, thus advancing the field through shared knowledge and tools.

Development of a whole-cell SELEX process to select species-specific aptamers against Aspergillus niger

BackgroundSpores produced by the filamentous fungus Aspergillus niger are abundant in a variety of environments. The proliferation of this fungus in indoor environments has been associated to health risks and its conidia can cause allergic reaction and severe invasive disease in animals and humans. Therefore, the detection and monitoring of Aspergillus conidia is of utmost importance to prevent serious fungal infections and contaminations. Among others, aptamers could serve as biosensors for the specific detection of fungal spores.ResultsIn this study, DNA aptamers specific to conidia of A. niger were developed by optimizing a whole-cell SELEX approach. Three whole-cells SELEX experiments were performed in parallel with similar conditions. Quantification of recovered ssDNA and melting curve analyses were applied to monitor the ongoing SELEX process. Next-generation sequencing was performed on selected recovered ssDNA pools, allowing the identification of DNA aptamers which bind with high affinity to the target cells. The developed aptamers were shown to be species-specific, being able to bind to A. niger but not to A. tubingensis or to A. nidulans. The binding affinity of two aptamers (AN01-R9-006 and AN02-R9-185) was measured to be 58.97 nM and 138.71 nM, respectively, which is in the range of previously developed aptamers.ConclusionsThis study demonstrates that species-specific aptamers can be successfully developed via whole-cell SELEX to distinguish different Aspergillus species and opens up new opportunities in the field of diagnostics of fungal infections.

A Bibliometric Review of Indoor Environment Quality Research and Its Effects on Occupant Productivity (2011–2023)

Over the past decade, there has been a growing recognition of the importance of indoor environmental quality (IEQ) in influencing occupant productivity. Researchers have studied various buildings, including offices, schools, hospitals, and residential settings, to understand the relationship between IEQ and productivity outcomes. Studies have taken a multifactorial approach, considering multiple aspects of IEQ. Evidence from the literature review suggests that the quality of the indoor environment is an essential factor that affects the productivity of building occupants, and it is one of the fundamental issues in the development of societies. This area of research requires the responsible participation of researchers at all levels, as there is significant scope to contribute to knowledge. Therefore, this study aims to conduct a bibliometric analysis of the published literature on indoor environmental quality and its impact on building occupant productivity through the scientific literature available from one of the largest and most famous academic databases, Scopus; the study was determined in 2011 to 2023. The search used differential thresholds for IEQ keywords affecting building occupant productivity. Three discrete queries were performed, resulting in approximately 3861 publications. These were filtered by reducing false positives and excluding publications irrelevant to the research topic. The final results were 72 publications. This study also used Excel and VOS viewer to analyse and create graphs and network visualisation maps to show the growth of publications and their types, active countries and institutions for recovered publications, international collaboration, author keywords, active journals, and citation analysis. This study can significantly advance our understanding of building occupant productivity and enhance quality of life and work. Evaluating the research outputs is essential for highlighting contributions to knowledge and global collaboration in this research area. The potential impact of this study is not just theoretical. It can shape the future of our built environments and the lives of those occupying them.

Post-occupancy evaluation (POE) of high-rise flats built using prefabricated prefinished volumetric construction (PPVC)

PurposeThere has been an increasing use of prefabricated prefinished volumetric construction (PPVC) in the construction of high-rise flats to enhance productivity and sustainability, but there have been little studies to evaluate if the use of PPVC satisfies construction quality and overall satisfaction with the flat. This study aims to evaluate how homeowners perceive living in PPVC flats after they have moved into their homes. This is done with a post-occupancy evaluation (POE) looking at total building performance (TBP) mandates covering spatial performance (SP), acoustics performance (AP), visual performance (VP), indoor air quality performance (IAQP) and thermal performance (TP).Design/methodology/approachData were collected through the use of a survey questionnaire which was developed based on literature review. The data gathered from 145 respondents were then analysed quantitatively using Jeffrey’s Amazing Statistics Program (JASP), Microsoft Excel and Comma-Separated Values (CSV) files. The data analysed were further validated through the use of interviews with industry professionals.FindingsBased on descriptive and inferential statistics, the key findings of this study are that most respondents are satisfied with their PPVC flats in terms of quality of construction, satisfaction, IAQP, TP, AP and VP. However, they are less satisfied with the interior of their PPVC flats.Originality/valueThis is the first ever POE in the world conducted with homeowners living in high-rise flats built using PPVC. The findings from the study highlighted homeowners’ concerns regarding the quality of construction, SP, and AP, particularly in the interior areas of the flats, and underscores the importance of considering homeowners' experiences and perceptions in the design and construction of PPVC housing.

Research on the thermal comfort of vertical radiant cold plate coupling with a new dual cold source dehumidification air conditioning system

Radiant cooling provides a completely novel air conditioning terminal that could provide better thermal comfort for the resident. However, the radiative system may encounter condensation issues under high-humidity environments. This article studies a radiant air conditioning system with dual-cold-source dehumidification which comprises a plate heat exchanger, a dual-cold fresh air dehumidifier, a capillary radiant cooling wall, and an air-source heat pump. The experimental results demonstrate a positive correlation between the temperature profile of the indoor air and the temperature distribution of the radiant cooling wall. Simulations were conducted to analyze the office’s air temperature and airflow velocity distributions under different supply air volumes and to assess thermal comfort employing computational fluid dynamics (CFD) software. The comfort levels with different air inlet positions are discussed. The simulation results demonstrate that the air conditioning system can maintain a high standard of comfort under an air supply of 350 m³/h.

Indoor air bacterial quality and associated factors in prison inmate cells of East Hararghe Zone and Harari Regional State, Eastern Ethiopia.

Bacterial indoor air load refers to the level of bacteria within and around dwellings and other structures. Pathogens, bacterial cell fragments, and bacterial organisms' byproducts can all pose major issues indoors, especially in prison inmate cells. However, there is lack of data on bacterial load and contributing factors in the East Hararghe zone and Harari regional state. The lack of studies on microbiological indoor air quality in prisons with contributing factors will therefore be filled by this investigation. The study aimed to assess bacterial indoor air load and contributing factors in prison inmate cells from October 1 to October 30, 2020. An institutional cross-sectional study was employed. All of the prisons in the East Hararghe zone and the Harari regional state served as the study's and source population. 62 prison cells were used in the investigation. Samples were obtained using the passively settling plate technique. The data were evaluated through the use of SPSS statistical software, Excel, and the statistical procedures of ANOVA, correlation, and chi-square test. The maximum and minimum bacterial loads, were recorded at 8:00 am (3027 CFU/m3) and 2:00 pm (1048 (CFU/m3) respectively. The correlation between the temperature and bacterial load was strongly positive (r = 0.680, p = 0.047), and the correlation of the moisture content and bacterial load was strongly negative (r = -0.671, p = 0.039). The levels of bacteria were higher than the guideline (2000 CFU/m3). While the relative humidity of indoor air was negatively correlated with bacterial load, temperature and bacterial load were significantly positively correlated. Harari regional state and East Hararghe zone prison commissions should be alarmed to alleviate these problems. The building standards need to be completely updated to the latest standards.