Room Ventilation Research Articles

The public-health significance of far-UVC-induced indoor ozone and its associated secondary chemistry.

There has been much recent interest in whole-room far-UVC (wavelength around 222 nm) to markedly and safely reduce overall levels of airborne pathogens in occupied indoor locations. Far-UVC light produces very low levels of ozone-in real-world scenarios induced ozone levels of less than 10 ppb, and much less in moderately or well-ventilated rooms compliant with US far-UVC dose recommendations, and very much less in rooms compliant with international far-UVC dose standards. At these very low ozone levels, there is no epidemiological evidence of increased health risks from any of the very large outdoor ozone studies, whether from ozone alone or from ozone plus associated pollutants. Indoors, at the low ozone concentrations of relevance here, ozone does not react rapidly enough with preexisting airborne volatile organic compounds to compete with even extremely low levels of room ventilation, so significant ozone-induced ultrafine particle production is very unlikely. Direct measurements in real-life room scenarios are consistent with these conclusions. A potential exception is the cleaning material limonene, which has an unusually high ozone interaction cross-section; in the far-UVC context, turning off far-UVC lights during cleaning with limonene products would be reasonable.

Quantifying Ventilation Design, Room Layout, and Occupant Activity Parameters during Aerosol-Generating Medical Procedures in Hospitals

The risk of airborne disease transmission in hospital rooms during aerosol-generating medical procedures is known to be influenced by the size of the room, air ventilation rate, input-to-output flow ratio, vent surface area, and vent location. However, quantitative recommendations for each ventilation design parameter are scarce. Moreover, room layout and occupant activity parameters, such as furniture locations and healthcare worker movement, are often omitted from studies on airborne disease transmission in hospital settings. As a result, the development of policies and technologies aimed at mitigating airborne disease transmission in hospitals has been limited. To address this shortfall, this study is aimed at first characterizing existing ventilation, room layout, and occupancy parameters in hospital rooms where aerosol generation medical procedures (AGMPs) occur and then testing the hypotheses that ventilation, room layout, and occupancy parameters vary significantly between hospital rooms and, in some cases, with time. Information on AGMPs was collected via a survey circulated to healthcare workers within British Columbia’s Interior Health Authority (IHA), while hospital room and ventilation system information was collected by reviewing drawing packages of 37 IHA hospital rooms. The survey results indicate that AGMPs commonly occur in trauma, ICU, or general ward rooms with positive or negative pressure ventilation systems. Statistical tests, with room type (trauma, ICU, or general), room pressure (positive or negative), and/or time as independent variables, show that variables relating to ventilation (number of supply vents, supply and exhaust vent location, ventilation rate, and supply and exhaust area) and room layout (congestion score, room volume, light area, and number of lights) vary with room type but not with room pressure. Occupant activity variables (number of workers, number of moving workers, and speed score) also vary with room type, although to differing extent with room pressure and time. The survey and drawing review data presented in this study can help guide systematic comparisons of mitigative technologies as well as parametric investigations on how room layout, ventilation, and operational parameters influence airborne disease spread. This is a crucial first step in achieving quantitative and clinically relevant recommendations for mitigating airborne disease transmission in healthcare settings.

Analysis of a reactive porous separation effects on depollution and indoor air quality: Application of LBM-MRT to heat and mass transfers

The reduction of energy demand and the indoor air quality associated with energy demand are the main goals of thermal buildings. This work is devoted to the study of the effect of a reactive porous separation on the ventilation (cooling) and depollution capacity in a rectangular room ventilated by air displacement. The model is considered as a cavity heated on its right verticle wall and thermally isolated by the other three walls. A porous separation divides the room into two compartments. The system of equations was solved using the Lattice Boltzmann method with multiple relaxation times. The extended Darcy Brinkman-Forchheimer model was used to simulate the porous material. An additional linear term is added to the standard transport equations (material diffusion) to account for reaction effects, this term was derived from Arrhenius' law. Over a wide range of Richardson and Darcy numbers, the results of the computations show the influence of these parameters on the flow structure, making it possible to categorize the different convection phenomena (natural, forced and mixed). The most important point to note is that the addition of reaction (fixing reaction) improves indoor air quality and can achieve a 55 % reduction in air renewal time, thus saving on energy costs. However, this reactif effect has no influence on the thermal efficiency of the proposed model.

Assessing the performance of the airflow window for ventilation and thermal comfort in office rooms

Assessing the performance of the airflow window for ventilation and thermal comfort in office rooms

Hybrid ventilation in residential and office buildings

This project is focused on hybrid ventilation systems, a combination of natural and mechanical ventilation in residential and office buildings. Especially in dwellings hybrid ventilation systems are quite common. For instance, this can be the frequently occurring combination of exhaust fans in bathroom and toilet and / or a range hood in the kitchen with window ventilation in the other rooms. Currently, these systems are part of the planning reality, however, there are neither planning aids nor focused building standards available. A recently completed research project documents the state of the scientific knowledge, identifies most common planning challenges, and thus provides the basis for future planning aids for hybrid ventilation. This paper sets out to define the term “hybrid ventilation”, presents the most common hybrid ventilation systems in Switzerland and gives planning guidelines for current components of hybrid ventilation systems.

Investigation on the unsteady ventilation performance of oscillating jet air supply through both spontaneous vortex street effect and active modulation

Ventilation is one of the most vital measures to create a healthy and comfortable indoor environment, significantly influencing indoor air quality and building energy consumption. The conventional steady-state airflow field of a ventilated room, if not reasonably configured, is prone to cause air stagnation in certain regions, whereas the unsteady airflow improves the mixing effect, which favors the dispersion and purging of indoor air pollutants. This paper proposes a method to induce an unstable air flow field utilizing the spontaneous Karman vortex street effect on the air-supply jet and swinging modulation. The quasi-periodicity of the airflow field and its influence on the indoor pollutant purging effect were investigated. The effects of air velocity oscillation and pollutant concentration decay in a ventilated room were studied through experimental measurements and computational fluid dynamics analysis. The results show that the transverse oscillation jet has a dominant period of 1.6 s and the longitudinal oscillation jet has a dominant period of 2.987 s, and both jets have a width about twice that of the free jet. The airborne pollutant discharge efficiency of the oscillating jet was higher than that of the free jet at the occupancy level, and the longitudinal oscillating jet purged pollutants faster than the transverse oscillating jet. This study reveals that oscillating jets can provide an option to create periodic flow fields and improve the efficiency of ventilation.

Assessment the operating room based on environmental factors and monitoring anesthetic gases in southwest of Iran

Background/objectivesOccupational exposure of employees to residual anesthetic gases in the operating room without a proper ventilation system can adversely affect their health. The purpose of this study was to assessment the environmental factors and monitoring the concentration of anesthetic gases in the operating rooms. MethodsTwenty-three operating rooms were examined. Simultaneously with each sampling, the temperature and humidity were measured with a moisture meter, a psychrometer, IR thermometer (Triplett MS475). The data was then analyzed using the Mann-Whitney and Pearson correlation tests. ResultsThe findings showed that the average concentration of isoflurane (P-value = 0.036) and sevoflurane (P-value = 0.049) were significantly higher in hospitals without ventilation system. Also, result of this study showed that the average level of isoflurane and sevoflurane (P-value = 0.315 and P-value = 0.120), there was no significant relationship in hospitals without cooler than hospitals with cooler system.Based on result this study, there was not found significant relationship between isoflurane and humidity (P-value = 0.586), isoflurane and temperature (P-value = 0.890), sevoflurane and humidity (P-value = 0.692), and sevoflurane and temperature (P-value = 0.199). ConclusionAccording to the results, the most important ways to reduce adverse health effects and reduce occupational exposure levels among employees and patients including the use of modern equipment, improvement of the operating room ventilation system, the use of a cleaning system closes to the exit pipe of the anesthesia machine, employee training, control of environmental factors (temperature and humidity), and frequent monitoring of anesthetic gases.

Experimental investigation of effect of ventilation strategies on the performance of cold storage

AbstractFresh fruits and vegetables are living organisms that require fresh air to survive while being stored. Respiratory gases can build up and damage produce if there is not enough ventilation during storage. Ventilation is required to prevent an excessive build‐up of respiratory gases and to maintain the freshness of produce. In hot and dry areas, air ventilation of refrigerated storage can have a negative impact on food produce quality and affect storage performance. An indoor experimental study was carried out to investigate the air ventilation of the cold room during various modes of air supply. The energy recovery device (ERD) with and without evaporative cooling arrangement is used in the air supply and the performance enhancement is compared. The ERD reduces the air ventilation load by more than 50% compared to direct ventilation of the cold room and consequently, it reduces the total power consumption of air ventilation. Furthermore, the overall cooling performance of the system is improved by up to 45.7% when the ERDs are used compared to the direct supply of fresh air during air change mode and the use of energy‐saving equipment has also proven improvements in the desired air conditions for food production.

Minimizing Defects in Radiator Grille Upper Garnish Parts using Six Sigma (DMAIC) at PT. AAS

To achieve quality improvement, companies must align their production processes with customer needs, control production costs effectively, and maintain product quality. This approach enhances customer satisfaction, increases market share, and boosts profitability. PT. AAS, an automotive company specializing in injection molding and painting, relies on resin as its primary raw material to produce car parts for major clients like Hyundai, Suzuki, and Astra. To dominate the market, PT. AAS must prioritize delivering quality products on time to earn customer trust and secure continuous orders. Initially, the QC data for the injection molding area showed a high defect rate of approximately 17.5% for the Garnish Radiator Grille Upper part, from December 2022 to May 2023. Prior to implementing the Six Sigma method, PT. AAS had a DPMO (Defects Per Million Opportunities) value of 58,177, equivalent to a 3.10 Sigma level. After applying the Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) process, the DPMO decreased to 17,991, resulting in a 3.60 Sigma level. This suggests that PT. AAS currently operates at a 4 Sigma level, with a strong potential to reach 5 or even 6 Sigma by addressing the root causes of rejection. The fishbone analysis highlights the need for action across all departments, including Management. Key areas to focus on include Material, ensuring the correct resin delivery to the Injection Molding station; Machine, verifying proper machine settings and utilizing the 5S methodology; Environment, optimizing room temperature and ventilation; and Man, providing training to enhance operators' knowledge and sense of responsibility.

Volume-targeted mask ventilation during simulated neonatal resuscitation

ObjectiveMask positive pressure ventilation (PPV) in the delivery room is routinely delivered with set peak inflation pressures. To aid mask PPV, stand-alone respiratory function monitors (RFMs) have been used in...

Comparison of ventilation techniques for compensation of mask leakage using a ventilator and a regular full-face mask: A bench study

BackgroundThe use of noninvasive ventilation (NIV) during and after extubation is common. We designed this study to determine the optimal strategy to compensate for mask leaks and achieve effective ventilation during NIV by comparing commonly used operating room ventilator systems and a regular facemask. MethodsWe tested four operating room ventilator systems (Dägger Zeus, Dägger Apollo, Dägger Fabius Tiro, and General Electric Healthcare Carestation 650) on a lung model with normal compliance and airway resistance and evaluated pressure control ventilation (PCV), volume control ventilation (VCV), and AutoFlow mode (VAF). We set the O2 flow at 10 L/min and the maximal flow at 13, 16, or 26 L/min. We simulated five leak levels, from no leak to over 40 L/min (I to V levels), using customized T-pieces placed between the lung model and the breathing circuit. We recorded the expired tidal volume (Vte) from the lung model and peak inspiratory pressure via two flow/pressure sensors that were placed distally and proximally to the T-pieces. Results1. Comparison of four ventilators: with any given ventilation mode, an increase in leak level caused a decrease in Vte. With PCV, only Zeus produced Vte larger than 150 ml at leak level V. 2. Effect of ventilation mode on Vte: across all four ventilators, PCV resulted in a higher Vte than VCV and VAF (P < 0.01). PCV mode with all ventilators at leak level II provided Vte values that were equal to or greater than those obtained with no leak. 3. Effect of O2 flow on Vte Using PCV mode: only Carestation 650 Vte at leak level II during PCV were significantly greater with 16 L/min O2 flow compared with 10 L/min O2 flow (P < 0.01). 4. Actual leak: increasing the O2 flow from 10 L/min to the maximum O2 flow dramatically increased the real leak with all 4 ventilators at any fixed leak level (P < 0.01). 5. Preset PIP vs. actual PIP with PCV: at low preset PIP and leak levels such as leak II and III, the discrepancy between preset PIP and actual PIP was small. The disparity between the preset and actual PIP grew when the target PIP and the leak level were raised. ConclusionFor NIV using a mask, the ventilator is preferred whose Pressure generator is Turbine, the PCV mode is preferred in the ventilation mode and the oxygen flow is set to 10 L/min or maximum oxygen flow.

A Case Study on the Variable Frequency Drive for Ship Engine Room Ventilation

Increasing ship energy efficiency is essential to reducing fuel consumption and ship-based harmful emissions. In a ship’s engine room, there are a lot of electric motors, and their energy consumption is remarkable. The effective operation of these electric motors becomes significant when taking into account ship energy efficiency with regard to the effects on the environment and climate change. The electrical, mechanical, and operational efficiencies of electric motors can be improved with a variable frequency drive. In order to improve the ship’s overall energy efficiency, the electric motors used for engine room ventilation are examined in this paper using variable frequency drives for two different ambient temperatures. Energy consumption of the engine room ventilation fans is calculated and the change in the efficiency depending on the air temperature is analyzed. By using data from actual crude oil tanker ships, the outcomes are compared with those of the traditional system. The results indicate an energy consumption reduction of more than 80% is achievable by using VFD electric motors for engine room fans. The result corresponds to 153.279 kWh of energy instead of 613.116 kWh annually.

Real-Time Measurements of Indoor-Outdoor Exchange of Gaseous and Particulate Atmospheric Pollutants in an Urban Area.

Air pollution is one of the greatest environmental risks to health, causing millions of deaths and deleterious health effects worldwide, especially in urban areas where citizens are exposed to high ambient levels of pollutants, also influencing indoor air quality (IAQ). Many sources of indoor air are fairly obvious and well known, but the contribution of outside sources to indoor air still leads to significant uncertainties, in particular the influence that environmental variables have on outdoor/indoor pollutant exchange mechanisms. This is a critical aspect to consider in IAQ studies. In this respect, an experimental study was performed at a public site such as a university classroom during a non-academic period in Madrid city. This includes two field campaigns, in summer (2021) and winter (2020), where instruments for measuring gases and particle air pollutants simultaneously measured outdoor and indoor real-time concentrations. This study aimed to investigate the dynamic variations in the indoor/outdoor (I/O) ratios in terms of ambient outdoor conditions (meteorology, turbulence and air quality) and indoor features (human presence or natural ventilation). The results show that the I/O ratio is pollutant-dependent. In this sense, the infiltration capacity is higher for gaseous compounds, and in the case of particles, it depends on the particle size, with a higher infiltration capacity for smaller particles (<PM2.5). Additionally, under specific situations of high atmospheric stability, the concentrations of gases derived from traffic tend to accumulate in the room, keeping the background concentrations. These concentrations decreased when room ventilation was produced simultaneously with well-ventilated (high wind speed) external conditions. This suggests that the meteorology and turbulence parameters played a key role in influencing indoor ambient pollution conditions by enhancing the dispersion or accumulation of pollutants. The obtained results highlight the high number of variables involved in the outdoor/indoor exchange of air pollutants and, consequently, how complex its study is. Thus, the knowledge of these factors is critical for understanding the behavior of indoor pollutants and controlling human exposure in indoor environments.

Numerical study on the indoor flow field and ventilation performance in the power room of a hybrid locomotive that passes through a tunnel

Under the background of energy saving, emission reduction, and green transportation, the electrification construction of railway lines is difficult owing to long cycles and high costs. Hybrid locomotives have emerged as fuel locomotives that can run on electrified lines and that achieve energy saving, emission reduction, and railway emergency on non-electrified lines. Train power equipment is highly integrated in the locomotive power room, which leads to the ventilation and heat dissipation performance of indoor high-heat equipment becoming one of the main factors that affect the safe operation of trains. This study focuses on the flow field and ventilation of locomotive power rooms in railway vehicle/tunnel systems and explores the variation of the ventilation flow rate and flow field in a power room when trains pass through a tunnel at different speeds. Based on the unsteady Reynold-averaged Navier–Stokes (RANS) equations and shear-stress transformation (SST) k-ω turbulence model, the relative motion between a train and a tunnel is simulated by sliding mesh, and the related algorithm settings are verified through experiments. The results show that: train speed is linearly related to the air inlet flow rate, and trains have a critical speed, which affects the original indoor air-cooling circulation system. This critical speed is reduced by the tunnel environment; The propagation and superposition of the pressure wave in a tunnel have no evident effect on the flow rate of the power room vent; Train speed is negatively correlated with the fan efficiency; thus, it deteriorates the fan efficiency in the tunnel environment; The symmetrical distribution of ventilation openings in a power room can effectively balance the fresh-air flow, but it is not conducive to cooling equipment located near the locomotive. These conclusions can contribute to improving future designs of the ventilation systems of hybrid electric locomotive power rooms.

Experimental analysis of airborne contaminant distribution in an operating room with different ventilation schemes

Experimental and numerical investigations were performed in a research operating room to compare laminar air flow and turbulent mixing ventilation systems in reducing the concentrations of airborne germs and surgical smoke in operating room air. In addition, measurements at scattered positions were conducted to find positions that are suited best for airborne monitoring in real-time during surgeries. In the experiments, particle counters were used to sample tracer aerosols originating from the wound area and the facial area of the thermal manikins representing surgical staff. The results showed that it is important to perform monitoring close to the areas with high hygiene requirements. Increasing the air change rate with turbulent mixing ventilation significantly reduced the number of airborne particles, however, not in the surgical microenvironment. Our findings show varying results considering the particle concentration using laminar air flow compared to turbulent mixing ventilation. With laminar air flow, higher contaminant levels are obtained in the areas with a high demand for contamination reduction. In contrast, laminar air flow was more effective in reducing the concentration of surgical smoke in the facial areas of the surgical staff. Regarding airborne germs, monitoring should be performed at the instrument tables and close to the wound area to evaluate the risk for surgical side infections. These results can support the development of guidelines and best practices for operating room ventilation design and maintenance to improve patient safety and reduce the risk of healthcare-associated infections.

Reversible decentralized ventilation: Experimental determination of efficiency by carbon dioxide level

We studied decentralized ventilation devices based on a regenerative heat exchanger with a reverse mode of operation. These devices are capable of recovering up to 90% of the heat used for ventilation of premises. They are a cheaper alternative to central units, and can solve the problem of high heat consumption for ventilation of buildings. Such devices are of little use in practice, since their efficiency concerning providing the required air exchange is poorly studied. The reverse mode of operation is not typical for room ventilation, since the same device constantly changes its purpose between supply and exhaust, which constantly changes the air distribution pattern in the room and can affect the efficiency of dilution and removal of harmful substances. Taking this fact into account makes the study original. The aim of the study is to experimentally determine the efficiency of ventilation in the premises of civil buildings when using such devices. The efficiency criterion was the level of carbon dioxide concentration in the room with a specified limit value of 1000 ppm. People were the source of carbon dioxide. Ventilation was represented by two decentralized devices. The experiment consisted in determining the level of carbon dioxide concentration in natural conditions with a different number of people in the room and different ventilation performance. The results of the experiment were verified by analytical determination of the level of carbon dioxide in the room. As a result of the experiment, dependences of changes in CO2 concentration over time were obtained when one, two and five people were in a room with and without ventilation. To ensure the level of carbon dioxide concentration below the limit (1000 ppm), the required ventilation capacity for one person was 40 m3/h, for two people – 80 m3/h, for five people – more than 160 m3/h. The results allow us to make conclusions about the efficiency of decentralized ventilation devices with reversible mode for premises with a small number of people.

Numerical study of indoor flow field and ventilation performance of the power room of a diesel locomotive under crosswind

Power room is the core part of the railway internal combustion locomotives, houses many high-power equipment within a limited space. The ventilation performance of a power room are the key factors that ensure the efficient operation of locomotives. Numerical simulations were conducted to study the indoor and outdoor flow fields of the power room, with focus primarily on the indoor flow field of the locomotive. The effects of locomotive and crosswind speeds on the ventilation performance and indoor flow field of a power room were studied. Furthermore, the effects of fan performance on the power room ventilation were compared and analyzed. The numerical methods used were verified using experimental data. Results showed that as locomotive speed increased, the power room ventilation performance decreased, while the airflow rate of certain power room air intakes increased, with an increase in locomotive speed. Crosswinds significantly increased the power room ventilation quantity, especially when the intakes faced the crosswind. When the crosswind speed surpassed a certain threshold, the intakes on the leeward side of the power room entered an air-leakage state. The indoor flow field distribution of the power room was unaffected by the fan performance. Though the effect of fan performance on the amount of airflow entering the power room varied, the fan performance positively correlated with the overall ventilation performance of the power room. Considering the strong airflow separation caused by the back-step corner of the driver cab, attention should be paid to the placement and intake position of the power room in the design stage.

Comparative Study of Natural Lighting Quality in Sharia Housing Based on Daylight Factor Evaluation Using Autodesk Revit

The Islamic residential concept is the famous tagline that several real estate developers chose for their housing products today; it attracts customer attention, primarily from the Muslim community. But only some housing products are suitable to all the ideal criteria of the Islamic Residential concept. Excellent Sharia housing must fulfill all Islamic residential concept requirements, including public facilities, open space, and building quality. The strategy of the ideal Islamic housing concept requirement is optimal natural light and ventilation in the entire room. The inner courtyard is one of the solutions to afford this strategy. The types of openings also affect the daylight penetration in a room. Autodesk Revit Simulation evaluates this research about the daylight factor aspect of Islamic housing in Sharia housing. The research method is a qualitative, quantitative, and comparatively mixed method. The minimum requirement of daylight factor for housing is 5%. The study object shows that in the case of Medina Residence 1, it sufficiently offers the most daylight factor affordability in a Sharia housing project. The research hypothesis is to maximize the daylight factor by modifying several types of windows and adding skylight openings to increase the daylight factor of the entire room. Increased wall window ratio and more inner open spaces are the solutions for the minimum size of the building site. In the case of Medina residence 1, the skylight opening can be applied, but the effect is less significant than making more openings facing the open space.

Protocol of randomized controlled trial comparing T piece resuscitator versus self-inflating bag for resuscitation in the delivery room in preterm neonates

Background: Neonatal resuscitation is a critical process for a newborn with effective ventilation as its key component. Three manual ventilation devices, including self-inflating bags (SIB), flow-inflating bags (FIB), and T-piece resuscitator (TPR) are recommended for positive pressure ventilation (PPV) in the delivery room. To date, there is insufficient evidence regarding the optimal device for establishing effective ventilation in newborns. This study is planned to compare the effectiveness of TPR and SIB during resuscitation. Methods: This will be a single centre, open-label, randomized controlled trial. Study participants will be preterm ≤34 of gestation needing PPV at birth as per NRP algorithm. Newborns will be randomly assigned to two groups (TPR or SIB). SpO2 at 2 and 5 min, time to reach heart rate &gt;100/min by pulse oximetry, and duration of PPV will be recorded. Primary outcome is need of delivery room intubation. Intention to treat analysis will be done using STATA version 17.0. A priori defined subgroup for purpose of analysis will be gestation ≤30 and 31-34 weeks. Trial will be done as per good clinical practice guidelines. Conclusions: If PPV with TPR is proven to be more efficacious in terms of less delivery room intubation, there would be a way towards finalizing the TPR as primary device for providing PPV during delivery room resuscitation at birth. This study has potential to bring down need of delivery room intubation with less duration of mechanical ventilation and morbidity in form of IVH, BPD and composite outcome of BPD and death. Trial registration: CTRI number: CTRI/2023/01/048660.

Bed-level ventilation conditions in daycare centers

In Dutch daycare centers, most often, semi-enclosed beds are used in bedrooms. Given that air usually does not mix completely in a ventilated room, there are concerns about whether room-level ventilation would be enough to keep the air clean inside semi-enclosed beds. No studies into the bed-level ventilation conditions in daycare centers have been identified. Therefore, a field survey was performed in 17 Dutch daycare centers to collect bedroom ventilation conditions and occupants’ characteristics. Based on that information, a full-scale bedroom identical to that of typical daycare centers was constructed in a climate chamber. The bed-level ventilation conditions were investigated by examining the dispersion and inhalation of CO2 gas exhaled by a breathing thermal baby model while sleeping in a bed. The effect of three variables, i.e., sleep positions (supine, lateral-to-wall, lateral-to-corridor), baby ages (12- and 30-month-old), and ventilation rates (55 and 250 m3/h), were studied. The results showed that excess exhaled CO2 concentration was accumulated inside the semi-enclosed bed in most cases. This indicates that bed-level ventilation conditions are not sufficient enough when only relying on the room-level mixing ventilation mode. The inhaled CO2 concentration of infants sleeping inside the bed was remarkably high, on average, three times higher than the measured values in the room exhaust. The study provides knowledge on the bed-level ventilation conditions in miniature semi-enclosed sleeping spaces under a mixing ventilation mode at room level and highlights the need to improve the air quality inside the baby bed.