Ventilated Compartment Research Articles

CFD and machine learning based hybrid model for passive dilution of helium in a top ventilated compartment

Abstract For hydrogen management in the containment of Nuclear Power Plants (NPPs), besides the Passive autocatalytic Recombiners (PAR), the passive dilution of lighter gas plays an important role. This could be an attractive option to optimize the containment design and to estimate the extent of dilution. Passive dilution has many other applications in nuclear industry. The experimental studies of air entrainment in the upward rising helium plume and the resulting dilution of helium gas by the Canadians in terms of Volume Flow Magnification Factor (VFMF) have been utilized for Computational Fluid Dynamics (CFD) validation. The CFD based Fire Dynamics Simulator (FDS) predicted values of VFMF found to be in good agreement with the test data. After FDS code validation, parametric study has been carried out to generate a data base of VFMF for range of hydrogen injection, side opening area and opening height. In present study various Machine Learning (ML) models are evaluated based on two-parameter relationship i.e. non dimensional hydrogen injection and VFMF using the CFD code generated database. The trained ML models were used for the predictions of the mass flow rate of gas entrainment (through opening) in the rising buoyant plume in terms of VFMF. The ML predictions were in good agreement with the predictions against test data. Multivariate Adaptive Regression Splines (MARS) based ML model found to performed best and discussed in the paper. The paper highlights details of methodology of numerical simulation, results of the CFD studies and machine learning based predictions.

Experimental and numerical study of an elevated pool fire scenario in a confined and mechanically ventilated compartment

The present work deals with an experimental and numerical investigation of an elevated pool fire scenario in a confined and forced ventilated compartment. Although often encountered in industrial installations or in common buildings, this type of configuration is rarely studied in the literature. This study is supported by a set of two large-scale fire experiments performed in the framework of the OECD-PRISME3 project and numerical simulations (RANS and LES methods) carried out with the CALIF3S-Isis software. The objective is to improve the physical understanding of the phenomena that are experimentally highlighted and to assess the capabilities of Computational Fluid Dynamics (CFD) on this type of configuration. First, the comparison between the two large-scale fire tests (one elevated and its equivalent on the ground) exhibits a strong modification of the fuel mass loss rate associated with a change in the thermal and species stratifications. Then, a preliminary simulation using a predictive approach commonly used and efficient for the case of a ground fire scenario shows by contrast its limitations when applied to the case of the elevated fire. Therefore, in addition to the essential step consisting in the validation of the code with a prescribed approach on this type of elevated fire, the simulations also reveal a specific phenomenology (smoke filling, strong vitiation, oxygen-pumping, …). Finally, taking into account these particularities allows in fine, for the studied case, the improvement of the prediction of the mass loss rate of the fire.

Effect of Opening Size on the Development of Ventilation-limited Fire

There are many factors, that affect the development of indoor fire, such as the size of the fire source, the opening or space of the room, and the nature of the combustible materials. Among them, the space of the room, has a significant impact on the development of a ventilation-limited fire. In this paper, the Fire Dynamics Simulator (FDS) software is used to analyze, the risk of fire initiation in the restricted ventilated compartment, when the size of vertical ventilation space is different. Through, a combination of experimental design, numerical simulation, and theoretical analysis, the changes in the level of carbon monoxide, visibility, temperature, Heat Release Rate (HRR) and, the smoke exhaust efficiency of natural smoke at different opening sizes are observed. It is observed that, when the ratio of inlet and outlet area reaches 2:1, the natural smoke exhaust effect is the best, however, the increasing in the opening size has little significance on the smoke exhaust effect. The research on the influence of smoke outlet size, will helps in the development of the law regarding fire prevention, smoke exhaust design, and fire rescue work of a building.

Development of the intellectual complex for parallel work of steam boilers

High rates of industrial and social progress require a sharp increase in heat generation on the basis of the powerful development of fuel and energy. Design of parallel operation of several boilers today is an important and necessary part of effective work in the workplace. Parallel connection of the boiler is made to: increase the maximum output and its subsequent progression, improve resiliency boilers, economical power consumption due to less loss of efficiency when operating at partial power, raising the living resource boilers, thrifty power consumption due to less loss of efficiency when operating at partial power, raising the living resource boilers, prevent local overheating and coking of tubes in the separation of heavy residues. Despite the significant advantages of using a parallel connection of the boiler there are problems such as a complex piping boiler, consumption of materials to connect the boiler, the increase in unforeseen expenditure. In the operation of the boiler unit therein may be damaged (piping, boiler elements accident water economizers) become unstable (water omission due to poor ventilation compartment exhaust emissions occur explosions and pops) that create dangerous situations fraught failure of the equipment or boiler unit as a whole, with the destruction of large material losses and loss of human life. A neural network is a system of contact between a simple processor whose operation is processing of received signals and send them to other CPUs. This processor is called a neuron. Artificial neural networks are selected for the development of process control systems due to the fact that they are fault tolerant. In a neural network information is distributed throughout the network, which means in case of failure of the neuron network behavior will be changed slightly, changing the behavior of neurons, but the network itself continues to operate successfully. Neural networks are not programmed in the usual sense of the word, they are trained. The possibility of training - one of the major advantages of neural networks over conventional algorithms. Technical training is to find the coefficients of the connections between neurons. During training, the neural network is able to identify the complex relationships between input and output data, and perform synthesis. This means that in case of successful learning network will be able to return the correct result on the basis of data that were not available in the training set.

Experimental study of flame extinction with fuel diffusion combustion inside a wall-opening compartment under reduced ventilation conditions

The present study investigates experimentally the transient flame extinction behavior with fuel diffusion combustion inside a wall-opening compartments at reduced ventilation condition. The characteristic parameters to quantify the flame extinction mechanism include the Global Equivalence Ratio (GER) extinction time and critical gas temperature right before extinction. Their coupling effect on the dynamic process of flame extinction with fuel diffusion combustion inside compartments of various scales and opening sizes is quantified and formulated. It is found that: (1) flame extinction is easier to occur for smaller opening size or relatively larger compartment scale which could be well represented by two non-dimensional quantities i.e. the GER and non-dimensional heat loss; (2) the time to reach flame extinction is shorter as the fuel supply flow rate is higher while it is longer as the opening size is larger; (3) the gas temperature inside the compartment when flame extinction is reached first increases with fuel supply rate until a plateau is reached. A formula is established to describe the critical gas temperature right before extinction as a function of a newly defined non-dimensional integrated parameter including both fuel combustion heat release and heat loss factors in which the fuel supply rate opening ventilation compartment scale and transient extinction time scale are involved in general to reflect physically their interplay in controlling the flame extinction inside the compartment. The present study provides new observation quantification and formulation of the mechanism of flame extinction with fuel diffusion combustion inside a wall-opening compartment under reduced ventilation condition.

Effects of elevated pool fire in a naturally ventilated compartment

This paper presents an experimental analysis of fire behavior due to elevated fuel pan with diesel in a fixed ventilated compartment of size 4 m (height) × 4 m (length) × 4 m (width) having door opening of 2 m (Hd) × 1 m (W). A reasonably large pool size of diameter 0.8 m is used in experiments so that the results may be useful for industrial fire hazard analysis. The variable parameter, taken as fire source height ‘h’ is from the floor that is 0.3 m, 0.6 m, 0.9 m, 1.2 m, 1.5 m and 1.8 m. During experimentation, it is observed that variation in pan height significantly affects the mass loss rate (MLR), heat release rate (HRR), flame behavior, smoke layer height, doorway mass flow and global equivalence ratio (GER). In case of higher elevated fire, HRR decreased drastically, one-fourth of maximum HRR value obtained in case of lower elevation of fire source. Lowest elevated pool fire shows good agreement for MLR and HRR with other experiment performed in an open space, i.e., well ventilated condition. For a significant elevated fire, the average fuel mass loss rate, flame temperature, smoke layer height, doorway mass flow rate and exit velocity were lower. With respect to above parameters, fire scenario inside the compartment seems to be less hazardous in case of higher elevated fire. A completely different trend has been found for the variation of GER with respect to MLR in current study.

Determination of Mass Loss Rate and Smoke Generated of Jordanian Hardwood Timber under Different Flaming Combustion and Limited Ventilation Environment

Natural wood has been used in structural applications for decades. Smoke from wood fires, additives and wood-protective coatings is a cause of death and serious injury in limited ventilation compartment. Ventilation restrictions in modern day designs complicate the combustion process and increase incomplete combustion products due to a reduction in the amount of oxygen available for fuel oxidation. Jordanian hardwood samples have been examined, tested and evaluated according to their mass loss rates, specific optical density, mass optical density, transmittance, and visibility using qualitative research used to realise the dynamics of fire phenomena. Four types of natural wood were tested under different heat fluxes with different Flaming combustion in a Smoke Density Chamber (SDC). The samples studied were Beech, Oak, Rhamnus, and Abies. The samples have been exposed to 25 and 50 kW/m2 heat fluxes in a limited ventilation compartment. Twelve samples were tested, each with dimensions of 75 x 75 mm and 10 mm thickness. An evaluation of the tested parameters, such as mass loss rate (MLR), specific optical density, transmittance, visibility and mass optical density (MOD have been carried out to determine their effectiveness as predictive parameters. Main results shows Beech has the lower values of specific optical density despite it has higher values of MLR% and MOD compared to other samples studied. Also, the mass loss rate (MLR %) increases with the heat flux even with different flaming conditions. In the opposite, there is a strong dependence for the mass optical density (MOD) on the heat flux and flaming conditions. Key conclusions have been drawn up that could be used in wood products and future works. The main objective of this work is to model the fire dynamic behavior in the pre-fire time. The results of this study can provide the bases for ventilation process and considerations of using natural woods in Jordan for different applications.

Fire development in multi‐compartment facilities: PRISME 2 project

Fire development in multi‐compartment facilities: PRISME 2 project

Repeatability assessment of large‐scale fire experiment involving water spray system in a forced ventilated compartment

SummaryRepeatability of large‐scale fire test remains a key issue for code validation process. Most of the large‐scale experimental studies are based on single experiment, and the influence of repeatability is barely considered in the test analysis process. Due to the substantial cost, reproducing several trials of a given large‐scale fire scenario is not often performed. In the framework of the OECD PRISME 2 project, this topic has been identified, and a specific large‐scale fire test has been reproduced twice in the final goal of assessing the level of repeatability. The scenario is an oil pool fire in an enclosure mechanically ventilated and during which a water spray system is activated. The analysis consists in identifying a set of variables on which metrics is applied in order to quantify the levels of discrepancy between the two tests. A set of 27 variables are selected such as they characterize the whole fire scenario (the fire source, the gas phase, walls, the ventilation network, and the water spray system). The analysis points out that the repeatability levels are different depending on the type of variable. The gas temperature or species concentrations are more repeatable than gas pressure or air flow rate. In addition, a new methodology is proposed in comparing, for each physical variable, the variations due to repeatability (ie, the precision) and the uncertainty. A new metric is proposed helping modelers in code validation process.

Spray fire induced gas temperature characteristics and correlations in a ceiling ventilated compartment

Spray fire, one of the common fires, often occurs in ship cabin and results in serious economic loss and casualties. However, there are few literatures [1–3] in terms of compartment spray fire, especially its gas temperature characteristics. Hence, a series of spray fire experiments were conducted in a 2 m × 2 m × 1.88 m ceiling ventilated compartment. It is found that the injecting pressure and ceiling vent size have significant effect on gas temperature. Gas temperature increases with the increase of injecting pressure and the increase in ceiling vent size results in a higher maximum gas temperature. The gas heat gain dominates the total heat transfer. The percentage of gas heat gain decreases with the ceiling vent size while the heat transfer through ceiling vent and compartment walls increases. For estimating the time-dependent average gas temperature in the combustion process, a simplified model was developed according to the thermal analyses, which shows good agreement with experimental data. Furthermore, based on M-Q-H method, a dimensionless analysis was performed for the total average gas temperature rise during the whole combustion process and the corresponding correlation was established, which can be applicable to estimate the gas temperature in ceiling ventilated compartment spray fire scenario.

THE DYNAMICS OF THE CONCENTRATION OF GASEOUS HARMFUL SUBSTANCES IN THE COMPARTMENT OF THE PRESSURE CHAMBER DO NOT HAVE THE TECHNICAL MEANS TO REMOVE THEM

Ventilation of the diving chamber compartment is a prerequisite for maintaining the concentration of harmful gaseous products of human metabolism is not higher than the maximum permissible values. The organization of ventilation of the compartment on the «open» cycle by blowing it with air or gas mixtures, leads to the need for a large stock of these components as part of the life support system of the chamber. The use of a «closed» ventilation cycle consisting in the transmission of air flow in the compartment of the pressure chamber through the cartridges for the removal of carbon dioxide and gaseous harmful impurities leads to a significant reduction in the need for fresh air, which is important in the creation of mobile barocompleses and in the modes of therapeutic recompression using helium gas mixtures. The article deals with the change in the concentration of harmful impurities of carbon monoxide, ammonia and acetone in the compartments of the chamber of different volumes in their ventilation on the «open» cycle, as well as on the «closed» cycle when using only the carbon dioxide removal unit. Due to the fact that there are several harmful substances in the atmosphere of the compartment at the same time, the assessment of their concentration was carried out with the use of the total toxicity index of the gas environment. On the example of the regime of training descents of divers and medical personnel to a depth of 100 m it is shown that the use of only the carbon dioxide removal unit in the ventilation compartment on the «closed» cycle leads to a significant excess of the maximum allowable toxicity index in the entire range of compartments, volume from 1,7 to 3,68 m3. It is shown that the duration of stay of people in the atmosphere with the level of toxicity exceeding the limit value depends on the volume of the compartment. The smaller the compartment, the faster the total content of harmful substances reaches the maximum permissible level of toxicity and the higher the content of harmful substances in the atmosphere of the compartment at the time of completion of the training descent. The results presented in the article indicate that with prolonged presence in the compartment of the chamber of people, ventilation of the compartment in a «closed cycle» using only the carbon dioxide removal unit is not permissible.

Generalized estimation of the ventilatory distribution from the multiple-breath washout: a bench evaluation study

BackgroundThe multiple-breath washout (MBW) is able to provide information about the distribution of ventilation-to-volume (v/V) ratios in the lungs. However, the classical, all-parallel model may return skewed results due to the mixing effect of a common dead space. The aim of this work is to examine whether a novel mathematical model and algorithm is able to estimate v/V of a physical model, and to compare its results with those of the classical model. The novel model takes into account a dead space in series with the parallel ventilated compartments, allows for variable tidal volume (VT) and end-expiratory lung volume (EELV), and does not require a ideal step change of the inert gas concentration.MethodsTwo physical models with preset v/V units and a common series dead space (vd) were built and mechanically ventilated. The models underwent MBW with N2 as inert gas, throughout which flow and N2 concentration signals were acquired. Distribution of v/V was estimated—via nonnegative least squares, with Tikhonov regularization—with the classical, all-parallel model (with and without correction for non-ideal inspiratory N2 step) and with the new, generalized model including breath-by-breath vd estimates given by the Fowler method (with and without constrained VT and EELV).ResultsThe v/V distributions estimated with constrained EELV and VT by the generalized model were practically coincident with the actual v/V distribution for both physical models. The v/V distributions calculated with the classical model were shifted leftwards and broader as compared to the reference.ConclusionsThe proposed model and algorithm provided better estimates of v/V than the classical model, particularly with constrained VT and EELV.

New developments in data regression methods for the characterization of thermal stratification due to fire

The study deals with the data regression methods used for validating zone code modeling in comparison with experimental fire tests. These methods aim at determining both the temperatures of upper and lower zones and the interface location calculated from experimental vertical temperature profiles. A new data regression method is proposed to improve the determination of upper and lower temperatures and position of the interface. This new method merges both the thermal stratifications showing constant temperature in the upper layer as often encountered for well ventilated fire (approach of Quintiere et al. [4]) and those showing constant gradient as often observed for fire in closed and forced ventilated compartment (approach of Audouin et al. [8,9]). These two latter existing methods and the new former one are then applied to large scale fire tests experiments performed in IRSN facilities. The major outcomes indicate that the most appropriate regression method depends on the basic shapes of the experimental vertical temperature profiles. The interface height is the most sensitive variable to the choice of the regression methods. Indeed, discrepancy higher than 100% can be found concerning this last variable. In contrast, the temperature of lower zone appears to be the less sensible variable. The discrepancy on the upper temperature is found also significant in some cases. From these investigations, guidelines are proposed to improve the data regression process needed for validating zone codes and are supported by a thorough analysis of these three data regression methods using experimental data from large-scale fire tests.

Experimental determination of fire heat release rate with OC and CDG calorimetry for ventilated compartments fire scenario

ABSTRACTThis research deals with the experimental determination of the heat release rate (HRR) of fires in mechanically ventilated compartments based on oxygen consumption (OC) and carbon dioxide generation (CDG) calorimetry. It proposes formulations for fire in force‐ventilated compartments on the same basis as the relations established for hood calorimetry in an open atmosphere but considering inertia and unsteady behavior of the fire via the time variation mass of O2 and CO2 in the compartment. The value of the new formulations of HRR has been tested in two series of propane gas fire experiments performed in a large‐scale facility. The first series involves a fire scenario with one compartment, and the second series, a fire scenario with three compartments connected to each other by doorways. In the first test series, the OC and CDG formulations for HRR are assessed. In the second test series, the OC and CDG formulations are presented with two approaches to definition of the control volume: approach involving three rooms and the flow rate in the ventilation network and approach involving only the fire room and the flow rate through the doorways. On the basis of the fire experiments considered, the most accurate method (accuracy to within 10%) for determining the HRR is the CDG formulation with approach for the control volume without considering the flow rates at the doorways. This analysis points out the different features of each method (OC and CDG) and thoroughly discusses their advantages and drawbacks. The overall analysis allows guidelines to be formulated for fire HRR calculation in confined and ventilated compartments. Copyright © 2013 John Wiley & Sons, Ltd.

Relative effects of inertia and buoyancy on smoke propagation in confined and forced ventilated enclosure fire scenarios

In this study, we focus on smoke propagation in confined and forced ventilated enclosure fire scenarios as it is a source of possible hazardous situations. The objective of the present contribution is to investigate the effect of the three physical mechanisms (buoyancy, gas expansion and forced ventilation) on diverse examples of smoke flow through transfer elements. Three types of pool fire scenario have been considered with several transfer elements typical of nuclear industry. The first scenario is a fire in one ventilated compartment and the propagation means are the release of smoke through the ventilation ducts. The second scenario is a fire in one ventilated room connected by a doorway to another ventilated room. The smoke flow investigated is the flow at the doorway. The last scenario is a fire in a ventilated compartment connected to an adjacent room with leakages. The smoke flow considered is a smoke leakage. Each scenario and the smoke propagation are analysed on the basis of large scale representative fire tests performed during the PRISME project and numerical simulations with a zone-modelling code, SYLVIA of IRSN. The results show ventilation is the driving mechanism for smoke propagation in the one-room configuration whereas buoyancy plays the major role for the doorway flow. Finally, depending on the kind of leakages, mechanical ventilation can act on the buoyancy-induced smoke propagation.

Determination of the heat release rate of large scale hydrocarbon pool fires in ventilated compartments

This contribution deals with the experimental determination of the Heat Release Rate (HRR) of hydrocarbon pool fires based on Oxygen Consumption (OC) and Carbon Dioxide Generation (CDG) calorimetry. This methodology, initially developed for open atmosphere fires, is modified for fires in ventilated compartments. The fire tests considered are under-ventilated large scale hydrocarbon pool fires in one confined and mechanically ventilated room. The formulation of the HRR for compartment application is presented as well as the fire experiments, the facility and the measurement techniques. This study presents the methodology that leads to the determination of the HRR and discusses the results and features of this method. First, the results of the mass balances of all species and soot within the compartment are presented and discussed. These are key elements to validate the accuracy of the HRR determination. Then, the calculation of the heat release rate with the two methods, OC and CDG, are presented. The OC methods give higher amplitude than the CDG methods. The effects of CO and soot production on the HRR calculation are discussed. This analysis points out the different features of each method (OC and CDG) and thoroughly discusses their advantages and drawbacks. The overall analysis gives guidelines for fire HRR calculation for fires in ventilated compartments.

Temperature and humidity control inside an automobile during heating period

This article investigates a control strategy for the automobile climate control problem; in particular, the heating mode in winter is considered when the initial car compartment temperature and outside temperature are colder than comfortable. By analyzing the air-conditioning processes involving the automobile air-handling unit operating in various weather conditions on a psychrometric chart, a control strategy is developed based upon the concept of conservation of sensible heat and latent heat. Irrespective of the car compartment's initial condition, the control strategy is to control air flow and mixed air temperature such that the compartment conditions in terms of temperature and humidity reach a set condition. The proposed strategy is composed of two parts. The first is to adjust air mass flow rate by balancing the latent heat transfer between ventilation and automobile compartment. Meanwhile, the second part is to control the percentage of heating air flow rate such that a precise temperature can be maintained. In short, balancing the sensible heat transfer among the air condition processes is essential to achieving temperature control, as variation in the net sensible heat will lead to changes in temperature. The proposed control strategy is evaluated in a Matlab/Simulink simulation environment. The results suggest that the proposed control strategy results in an improved indoor humidity level when compared to traditional fuzzy control.

A kinetic model for human blood concentrations of gaseous halocarbon fire-extinguishing agents

A simple kinetic model for calculating the blood concentration history of humans exposed to time-varying concentrations of gaseous, halocarbon fire-extinguishing agents is described. The kinetic model was developed to extend experimental physiologically based pharmacokinetic (PBPK) models for arterial blood concentration of halocarbons, obtained from constant concentration exposure of dogs to time-varying exposure conditions for humans. In the present work, the simplified kinetic model was calibrated using published PBPK-derived arterial concentration histories for constant concentration exposure to several common fire-extinguishing agents. The calibrated kinetic model was then used to predict the blood concentration histories of humans exposed to time-varying concentrations of these fire-extinguishing agents in ventilated compartments and the results were compared with PBPK-derived data for the agents. It was found that the properly calibrated kinetic model predicts human arterial blood concentration histories for time-varying exposures as well as the PBPK models. Consequently, the kinetic model represents an economical methodology for calculating safe human exposure limits for time-varying concentrations of gaseous halocarbon fire-extinguishing agents when only PBPK-derived human arterial blood concentration histories for constant exposure conditions are available.

Experimental Studies on Water Mist Suppression of Liquid Fires with and without Additives

The purpose of this article is to examine the effect of additives on the extinguishment of liquid pool fires with water mist. Tests are conducted using gasoline, diesel, and ethanol pool fires in a 3.0 × 3.0 × 3.0 m well ventilation compartment. The additives included representative kinds of metal compound, NaHCO3, film-forming agent, AFFF, and a multi-component agent, MC additive. Results showed that the suppression performance varied greatly depending on fuel type, additive type, and concentration. The higher the fire point, the easier it is to extinguish the hydrocarbon liquid pool fires with water mist. But for the polar fuel, small fractal flames existing around the pool edge after the fire is suppressed increased the suppression difficulty. The benefit of adding film-forming additives is observed in the suppression of hydrocarbon fires when forming a thin film layer by fluorinated surfactant on the surface. However, too much film-forming additive decreased the marginal fire extinguishing effectiveness due to the saturation effects of surfactants. Addition of a small quantity of film-forming additives did not improve the performance of water mist for ethanol fires, which is considered to be eroded by the fuel. Addition of metal compounds increased the effectiveness of water mist gradually both for ethanol and hydrocarbon fires, but there also existed upper agent limit because of the associated limiting vapor pressure of the active metal compound. The multi-component additive showed a combined suppression effect of film-forming agent and metal chemicals. It effectively extinguished both ethanol and hydrocarbon fires though coupling the physical and chemical fire suppression mechanisms and seems worth further exploration.

Can new pulmonary gas exchange parameters contribute to evaluation of pulmonary congestion in left-sided heart failure?

Assessment of pulmonary congestion in left-sided heart failure is necessary for guiding anticongestive therapy. Clinical examination and chest x-ray are semiquantitative methods with poor diagnostic accuracy and reproducibility. To establish reference values, describe reproducibility, and investigate the diagnostic and monitoring properties in relation to pulmonary congestion of new pulmonary gas exchange parameters describing ventilation/perfusion mismatch (variable fraction of ventilation [fA2] or the drop in oxygen pressure from the mixed alveolar air of the two ventilated compartments to the nonshunted end-capillary blood [DeltaPO(2)]) and pulmonary shunt. Sixty healthy volunteers and 69 patients requiring an acute chest x-ray in a cardiac care unit were included. The gas exchange parameters were estimated by analyzing standard bedside respiratory and circulatory measurements obtained during short-term exposure to different levels of inspired oxygen. Nine patients were classified as having pulmonary congestion using a reference diagnosis and were followed during 30 days of anticongestive therapy. Diagnostic and monitoring properties were compared with chest x-ray, N-terminal probrain natriuretic peptide (NT-proBNP), spirometry values, arterial oxygen tension, alveolar-arterial oxygen difference and venous admixture. The 95% reference intervals for healthy subjects were narrow (ie, fA2 [0.75 to 0.90], DeltaPO(2) [0.0 kPa to 0.5 kPa] and pulmonary shunt [0.0% to 8.2%]). Reproducibility was relatively good with small within subject coefficients of variation (ie, fA2 [0.05], DeltaPO(2) [0.4 kPa] and pulmonary shunt [2.0%]). fA2, DeltaPO(2) and NT-proBNP had significantly better diagnostic properties, with high sensitivities (100%) but low specificities (30% to 40%). During successful anticongestive therapy, fA2, DeltaPO(2), NT-proBNP and spirometry values showed significant improvements. The gas exchange parameter for ventilation/perfusion mismatch but not pulmonary shunt can have a possible role in rejecting the diagnosis of pulmonary congestion and in monitoring anticongestive therapy.