Barometric pressure variation

Air tightness of Australian buildings is a great unknown. Despite testing methods being developed and implemented in many advanced European and North American countries, this has not happened in Australia. This paper notes energy efficiency gains that can be achieved through tighter construction, and follows on from the investigation into testing methodology and literature discussed in TEC 23: Air Leakage in Buildings -Review of International Literature and Standards. Several domestic case studies are used to implement two accepted testing methods and aid to build the case for increased awareness of airtight housing in Australia.

This article considers a new type of air infiltration through building envelopes caused by the barometric pressure variation. This process is independent from wind action or stack effect. A new building–atmosphere differential equation of air exchange is established. Based on the solution of the differential equation of air exchange, we propose the notion of pressure equilibration time [Formula: see text] that characterizes the dynamic response of the building. Furthermore, experimental climatic data were processed using Fourier analysis methods in order to build an identification model based on the regular harmonics of external pressure oscillation. The barometric pressure reconstructed in its parameterized form was introduced in the differential equation of air exchange as a term that models the dynamics of the external action. The analytic solution of the differential equation of air exchange demonstrates that the indoor–outdoor pressure difference is insignificant at less than 1...

• Nouveaux paradigmes pour une meilleure appréhension et gestion de la Tension Artérielle (ou Pression Artérielle),

• La place de la Tension Artérielle dans la survenue et le développement du Glaucome Évolutif à Pression Normale (GEPN <- PPO), et

• Risques de l’obésité et du diabète sur la vue.

The purpose of this study was to determine whether the weather – specifically changes in barometric pressure – affects the behavior of students with ASD/AS in the classroom. The motivating factors for this capstone were: 1) a desire to provide factual evidence to support primarily anecdotal evidence regarding the correlation between student behavior and the weather; 2) to contribute to an area of research that is lacking in data. The author traces the effects of weather on humans throughout history and proposes that since students with ASD/AS can experience hypersensitivity or hyposensitivity, they can be extra sensitive to atmospheric changes in pressure, ultimately resulting in changes in classroom behavior. Data collected over an 8 week period was statistically analyzed using two different methods: Pearson linear and Spearman non-normal correlation; it was also graphed and qualitatively analyzed. The statistical analysis did not support the hypothesis, but the topical analysis found that there is a change in behaviors when there is a significant change (> 0.10 Hg) in pressure.

This article considers a new type of air infiltration through building envelopes caused by the barometric pressure variation. This process is independent from wind action or stack effect. A new building–atmosphere differential equation of air exchange is established. Based on the solution of the differential equation of air exchange, we propose the notion of pressure equilibration time [Formula: see text] that characterizes the dynamic response of the building. Furthermore, experimental climatic data were processed using Fourier analysis methods in order to build an identification model based on the regular harmonics of external pressure oscillation. The barometric pressure reconstructed in its parameterized form was introduced in the differential equation of air exchange as a term that models the dynamics of the external action. The analytic solution of the differential equation of air exchange demonstrates that the indoor–outdoor pressure difference is insignificant at less than 1...

Background: Contamination of operating room air is associated with increased risk of surgical site infection. Door opening events occur often during surgery. The effect of door opening on room pressure and contamination is investigated, and detection of door opening events via a single internal barometric pressure sensor is demonstrated. Methods: A single barometric pressure sensor stationed in a corner away from the door was used to measure room pressure in a simulated OR with air flow conditions of 20 ACH and a positive pressure of approximately 7.5 Pa. A laser-based particle counter was used to measure particle levels during a series of 20 periodic door opening events. Results: The average (standard deviation) detected room pressure in the OR under positive pressure decreased by approximately 6.5 (1.2) Pa (p>3 × 10 − 17). When the door is closed the pressure returns. Initial airborne particle levels in the room were 36 (6) /ft 3. 20 periodic door openings performed over 40 min. resulted in particle levels exceeding 200/ft 3. Conclusions: OR barometric pressure decreases and recovers when the door to an OR under positive pressure is opened and closed and provides a detectable signal for passively monitoring and tracking door openings. The number of particles in the unoccupied OR increases as increasing numbers of door opening events occur.

The European Union is promoting renewable sources by searching new ways of saving energy in order to minimize the impact on the environment of the conventional power plants. The research focuses on the importance of renewables in energy balance of the Passive House during warm season. Secondly, it was analysed the influence of the environment on the behaviour of the low energy building. For study, it was analysed the Passive House located in the University Politehnica of Bucharest campus. The monitoring system installed acquires information about indoor comfort level and energy balance between house, grid and photovoltaic system.

Air infiltration holds a central role in building energy consumption and is associated to several building physics phenomena. Air infiltration in buildings due to wind-induced pressure is a complex process, strongly influenced by the turbulent nature of wind. This extended summary highlights the findings of a series of studies with focus on unsteady wind and its impact on air exchangesin buildings. The focus is on wind gustiness and its relation to air infiltration under natural conditions. Wind spectrum analysis shows that high-frequency wind gusts provide important information, while only considering mean wind speed and direction are not adequate to predict air exchanges in buildings. The impact of gustiness becomes greater for evenly distributed leakages between windward (upstream) and leeward (downstream) façade. Infiltration measurements under unsteady wind can vary significantly from results estimated based on pressurization measurements. In addition, wind gustiness is respons...

Uncontrolled leakage paths in a building have been very clearly stated as an important reason for energy loss. While steady state conditions have been studied in detail there are only few studies that discuss the influence of natural unsteady phenomena to the infiltration rates of a building. In the current numerical study, unsteady wind conditions are performed around a single-room model. Two scenarios of wind gust frequency and five angles of wind direction are employed, while variable leakage areas are simulated and solved in a transient mode, aiming to investigate the variation of the air exchange rates (ACH). The results show large differences between ACH under high wind gust frequency compared to the scenario of the low one, rising up the uncertainty of estimating the infiltration rates of a building. In addition, wind direction is a factor that could also cause significant variations on the leakage rates. However, it seems that when the gust frequency is high then even the ob...

Requirements for measuring the building airtightness have been proposed and included by many countries for national regulations or energy-efficient programs to address the negative effect of poor airtightness on building energy performance, durability and indoor environment. The methods for measuring building airtightness have continuously improved and evolved over a number of years. At present, the well-established and widely accepted method for quantifying the building airtightness is the fan pressurisation method (blower door being the most wellknown), which can be implemented by pressurising the test building to a range of high pressures (usually in steps across 10–60 Pa range) and measuring the corresponding fan flow rate. As an alternative method, the Pulse technique can be utilised to measure building airtightness at low pressures (typically at 4Pa) by rapidly releasing a 1.5-second pulse of air from a pressurised vessel. It is known that the outdoor weather condition and in ...

During the past ten years, the means of ventilating single-family residences has received considerable attention. In many areas, the use of natural ventilation for infiltration has either come under close scrutiny, or has already been supplanted by mechanical ventilation systems. To evaluate the energy efficiency and ventilation effectiveness of both mechanical and natural ventilation strategies, both complex and simplified infiltration models are used. This paper examines the inaccuracies associated with using simplified models to compare ventilation strategies. Two simplified techniques for combining mechanical ventilation flows to the flows caused by wind and stack effects are examined. The simplified combination techniques are compared with the results obtained with an iterative flow-balance simulation. The flow-balance simulation determines the ventilation by balancing the incoming and outgoing flows under the pressure conditions resulting from the combination of wind effect, s...

The human body is a highly aerobic organism, in which it is necessary to match oxygen supply at tissue levels to the metabolic demands. Along metazoan evolution, an exquisite control developed because although oxygen is required as the final acceptor of electron respiratory chain, an excessive level could be potentially harmful. Understanding the role of the main factors affecting oxygen availability, such as the gradient of pressure of oxygen during normal conditions, and during hypoxia is an important point. Several factors such as anaesthesia, hypoxia, and stress affect the regulation of the atmospheric, alveolar, arterial, capillary and tissue partial pressure of oxygen (PO2). Our objective is to offer to the reader a summarized and practical appraisal of the mechanisms related to the oxygen&#39;s supply within the human body, including a facilitated description of the gradient of pressure from the atmosphere to the cells. This review also included the most relevant measuring me...

Air infiltration contributes to a heat loss typically representing up to one third of the heating demand of a building. The building airtightness, also quantified as air leakage, is the fundamental building property that impacts infiltration. The steady (de)pressurization method (blower door) is the widely accepted standard process for measuring building air leakage. However, this method requires the enclosure to be pressurised to a typical range of 10-60 Pa, which is not physically representative of the pressures experienced by buildings under natural conditions. The Pulse technique is a novel alternative method, which measures air leakage at low pressures; quoting it at a reference pressure of 4 Pa. An experiment was designed to test the leakage characteristics of a detached house in the UK and compare them with the infiltration rate; which were measured by tracer gas techniques, utilising the decay method. The blower door and Pulse tests were both performed multiple times during ...

Mechanical positive input and extract ventilation are common strategies employed in English houses, generally because they provide adequate indoor air quality and specifically because they are effective at minimizing mould growth and its associated negative health consequences. Air is either exclusively supplied or extracted (never both) by a mechanical system at a prescribed airflow rate designed to ensure adequate indoor air quality. The remaining airflow, required to balance mass through the building, occurs through the fabric, through a mix of purpose provided and adventitious airflow paths. However, there is an important need to reduce adventitious airflow during the heating season in order to save energy and this is highlighted by the building standards of many countries who advocate increasing the airtightness of their housing stocks. Increasing a fabric&#39;s airtightness also increases its resistance to airflow and so a positive displacement or extract ventilation system mu...

The classical barometric formula used in atmospheric models is derived neglecting the presence of chemical reactions in the atmosphere. However, many chemical reactions are continuously taking place either promoted by sunlight or simply by the thermal motion of the molecules. In this report, the effect of chemical reactions on the barometric formula will be modeled and discussed. Such effect is not only related to individual molecular concentration profiles but also to thermal profiles when the heat of reaction is considered. The derivation of the model is based on a simple reversible chemical reaction, but it is also generalized for any arbitrary set of chemical reactions taking place in the system. Even under the steady-state assumption, the differential equations obtained do not provide a direct analytical solution and therefore, they must be numerically integrated. A particular example is presented for illustrating the model obtained but also the numerical solution method.

Pascal's law, while originally proposed for liquids, has usually been considered valid also for gases. However, the fact that the molecules in a gas are separated from each other beyond their spheres of action most of the time, does not allow the direct transmission of the weight of the gas in the vertical direction. Undoubtedly, the mass of gas and the gravitational acceleration influence the pressure of the gas, but not according to Pascal's law. Although a previously reported mathematical model of the motion of gas molecules supports this idea, an additional experimental verification is presented in this report. The validation of Pascal's law in gases is done considering the effect of differential air pressure on the acceleration of a body during free fall, particularly for low-density bodies. The free fall experiments were done considering four boxes (made of paper) of different sizes and densities, showing significantly lower free fall accelerations (p-value < 2.2x10^-16), compared to the predictions obtained assuming the validity of Pascal's law in gases.

This article considers a new type of air infiltration through building envelopes caused by the barometric pressure variation. This process is independent from wind action or stack effect. A new building–atmos-phere differential equation of air exchange is established. Based on the solution of the differential equation of air exchange, we propose the notion of pressure equilibration time 50 that characterizes the dynamic response of the building. Furthermore, experimental climatic data were processed using Fourier analysis methods in order to build an identification model based on the regular harmonics of external pressure oscillation. The barometric pressure reconstructed in its parameterized form was introduced in the differential equation of air exchange as a term that models the dynamics of the external action. The analytic solution of the differential equation of air exchange demonstrates that the indoor–outdoor pressure difference is insignificant at less than 10 À3 Pa for any harmonic of the external pressure variation. At the same time, it is concluded that the airtightness of the envelope has little influence on the process, as the indoor–outdoor pressure equilibration is almost instantaneous in a continuous regime of variation. The described mechanism of air infiltration explains the alternation of infiltration and exfiltration of air in buildings. For this, a mass balance of air exchange for the specific ranges of time is performed. We prove that the barometric pressure variation has an effect that accounts for 3.19% of the total quantity of air exchanged. The advances provided by this paper constitute a useful instrument for further studies concerning the stack effect in thermal dynamic conditions. Practical application: The paper proposes a novel methodology of determining the air exchange build-ing–environment by considering a new component of infiltration and its cyclic variation: the barometric pressure. A new mechanism of natural air infiltration is determined and modeled and it should be added to the existing ones: wind action and stack effect. A complete methodology of analysis and extraction of the cyclic processes hidden in an envelope of stochastic variations is defined and applied with the support of signal processing techniques and spectral analysis. The refinement of the mathematical instrument was able to distinguish through a deterministic approach an influence of 3.19% of the new barometric component. Furthermore, with few adaptations, the methodology constructed in this study can be applied for investigation of the stack effect by considering the cyclic variation of the atmospheric temperature. Currently, the stack effect is analyzed only for average conditions of temperature, a simplistic approach that suggests a large potential for further improvement.

Heat loss throughairinfiltrationcan reach50% of totalin a buildingfrom the interactionwith the external environment. Tolimitor controlairinfiltrationinbuildingsrequires acorrect estimate of them based onseveral models. From thetechnicalliteratureare foundvariousevaluation algorithmsstarting fromtheusual"rule of practice" to rigorous analyticalalgorithms. This studyaims atpresentingvariousexistingmodelsfor estimatingair leakage, and also it is builta new algorithmto evaluate thenatural infiltrationof the air through the envelope, taking in consideration the cyclicvariation of theatmospheric pressure.