Les filtres plissés à très haute efficacité (THE) jouent un rôle essentiel dans le maintien du confinement des installations industrielles à risques, les réacteurs nucléaires par exemple. Ces filtres permettent le piégeage des aérosols, qui sont la principale source de contamination externe. Dans ce cadre, l’IRSN (Institut de Radioprotection et de Sûreté Nucléaire) conduit des études pour caractériser les performances des filtres THE. L’objectif de la présente thèse a été de développer un modèle prédictif décrivant l’évolution de la résistance aéraulique du filtre au cours de son colmatage. Le colmatage d’un filtre plissé THE est piloté, d’une part par les conditions aérauliques imposées dans les réseaux de ventilation, d’autre part par la nature du média et les propriétés des particules collectées par le filtre. Ainsi, les travaux réalisés ont été répartis sur deux volets. La première partie a été dédiée à l’étude de l’aéraulique du filtre suivant une approche double expérimentale et numérique. Un banc expérimental permettant de mesurer les champs de vitesse dans un pli de filtre plissé THE a été développé. Les mesures réalisées ont servi à la validation des codes de calcul utilisés (ANSYS CFX® et GeoDict®) et au développement d’un modèle de perte de charge initiale des filtres plissés vierges. Une validation du modèle à l’échelle de filtres complets avec des géométries différentes a ensuite été effectuée. La deuxième partie a porté sur l’étude du colmatage des filtres plissés THE suivant une approche expérimentale et numérique. Un banc expérimental a été développé pour la détermination des paramètres entrant en jeu dans les modèles de colmatage (porosité, taille de particules …), puis des simulations numériques à l’aide du logiciel GeoDict ont été réalisées pour caractériser la croissance du dépôt sur la média. La combinaison des résultats expérimentaux et numériques a conduit au développement d’un modèle décrivant l’évolution de la résistance aéraulique du filtre THE au cours de son colmatage avec des particules microniques / High Efficiency Particulate Air (HEPA) pleated filters are used to ensure the containment of airborne contamination within nuclear facilities. These filters are often the last barrier before a potential release of radioactive substances into the environment. Predicting their performances (pressure drop and efficiency) is a main thrust of research for IRSN which aims at avoiding any unexpected failure of those devices on French nuclear facilities. The clogging phenomenon is mainly influenced, on one side, by the flow conditions imposed in the ventilation network and, on the other side, by the media characteristics and the particles properties which are collected by the filter. Consequently, the work carried out has been divided into two parts. In the first part, we focused on the study of the airflow behavior within a HEPA pleated filter with an experimental and numerical approach. An experimental bench has been developed to measure the airflow field at the entrance channel of a HEPA filter pleat. Then, the experimental measurements have been used to validate GeoDict® and ANSYS CFX® simulations. The combination of the experimental and the numerical results have been used to develop a model to predict the evolution of the initial HEPA filter pressure drop. The work performed in the second part deals with the clogging of the filter. An experimental bench, dedicated to the characterization of the parameters that intervene in the clogging models such as the porosity, the pressure drop and the particles size, has been developed. Then, numerical simulations conducted with GeoDict® have been realized to describe the cake formation on the surface of a HEPA pleated filter. Finally, we developed a model to predict the evolution of HEPA pressure drop during clogging with micronic particles

Infecções fúngicas invasivas têm emergido como causa de alta morbimortalidade entre pacientes com neoplasia hematológicas, principalmente os submetidos a transplante de células-tronco hematopoéticas (TCTH). Fungos estão onipresentes na natureza, logo, medidas com o objetivo de reduzir a carga fúngica em ambientes hospitalares têm sido preconizadas. No presente estudo, foi realizada coleta de fungos no ar em dois centros de referência em TCTH do sul do Brasil, que possuem instalações distintas, assim como diferentes formas de controle de ar. Todos os quartos do hospital 2 são equipados com filtro de partículas de ar de alta eficiência (HEPA), enquanto no hospital 1 não há sistema específico de filtragem do ar; além disso, os pacientes internados no hospital 2 são de maior risco para doença fúngica invasiva, em função de fatores relacionados ao hospedeiro. Foram realizadas 130 coletas de ar no período de dezembro de 2009 a janeiro de 2011, sendo as amostras provenientes de quartos, banheiros e corredor. Para fins de análise, os fungos pertencentes ao gênero Aspergillus, Rhizopus e Fusarium foram considerados como fungos filamentosos potencialmente patogênicos, enquanto os demais fungos foram classificados como ambientais. A comparação entre os corredores dos hospitais 1 e 2 não mostrou diferença quanto a quantidade de fungos isolados (p=0,114 para fungos ambientais e p=0,622 para fungos filamentosos potencialmente patogênicos). Já os quartos de ambos os hospitais apresentaram redução significativa na quantidade de fungos filamentosos potencialmente patogênicos, quando comparados com os corredores (p<0,0001). Comparando-se os quartos dos hospitais 1 e 2, observou-se menor quantidade de fungos ambientais no hospital 2 (p<0,0001); contudo, para fungos filamentosos potencialmente patogênicos não se encontrou diferença (p=0,7145). Durante o período de estudo, a incidência de doença fúngica invasiva por fungos filamentosos foi de 2,1% no hospital 1 e 7,6% no hospital 2. A baixa carga fúngica nos quartos do hospital 1 poderia ser explicadas pelo uso de medidas protetoras adicionais, incluindo janelas e portas fechadas, reforçando-se a importância de tais medidas no cuidados em ambientes protegidos. / Invasive fungal infections have emerged as a cause of high morbidity and mortality among patients with hematologic malignancies, especially among those undergoing hematopoietic stem cell transplantation. Fungi are ubiquitous in nature, therefore measures aimed at reducing fungal burden in hospitals have been emphasized. In this study air samples were collected in two HSCT centers in Southern Brazil, which have distinct facilities, as well diferent air control systems. All rooms of hospital 2 are equipped with HEPA filters. In addition, patients hospitalized in this unit are at a higher risk for invasive fungal diseases. A total of 130 samples were obtained during December 2009 to January 2011 from rooms, restrooms and corridors. For analysis, all fungi belonging to the genus Aspergillus, Rhizopus and Fusarium were considered filamentous fungi potentially pathogenic, while others were considered environmental fungi. The comparison between corridors of hospital 1 and 2 showed no difference in fungal concentration (p=0.114 for environmental fungi and p=0.622 for potentially pathogenic). The rooms of both hospitals showed a significant lower concentration in PPF, as compared to corridors (p<0.0001). Comparing rooms of hospital 1 e 2 there was a lower amount of environmental fungi in hospital 2 (p<0.0001) – however no difference was observed for potentially pathogenic (p=0.714). During the period of study, the incidence of invasive mold infection was 2.1% in hospital 1 and 7.6% in hospital 2. The low fungal burden in rooms in hospital 1 may be explained by the implementation of additional protective measures, emphasizing the importance of such measures in protected environments.

Infecções fúngicas invasivas têm emergido como causa de alta morbimortalidade entre pacientes com neoplasia hematológicas, principalmente os submetidos a transplante de células-tronco hematopoéticas (TCTH). Fungos estão onipresentes na natureza, logo, medidas com o objetivo de reduzir a carga fúngica em ambientes hospitalares têm sido preconizadas. No presente estudo, foi realizada coleta de fungos no ar em dois centros de referência em TCTH do sul do Brasil, que possuem instalações distintas, assim como diferentes formas de controle de ar. Todos os quartos do hospital 2 são equipados com filtro de partículas de ar de alta eficiência (HEPA), enquanto no hospital 1 não há sistema específico de filtragem do ar; além disso, os pacientes internados no hospital 2 são de maior risco para doença fúngica invasiva, em função de fatores relacionados ao hospedeiro. Foram realizadas 130 coletas de ar no período de dezembro de 2009 a janeiro de 2011, sendo as amostras provenientes de quartos, banheiros e corredor. Para fins de análise, os fungos pertencentes ao gênero Aspergillus, Rhizopus e Fusarium foram considerados como fungos filamentosos potencialmente patogênicos, enquanto os demais fungos foram classificados como ambientais. A comparação entre os corredores dos hospitais 1 e 2 não mostrou diferença quanto a quantidade de fungos isolados (p=0,114 para fungos ambientais e p=0,622 para fungos filamentosos potencialmente patogênicos). Já os quartos de ambos os hospitais apresentaram redução significativa na quantidade de fungos filamentosos potencialmente patogênicos, quando comparados com os corredores (p<0,0001). Comparando-se os quartos dos hospitais 1 e 2, observou-se menor quantidade de fungos ambientais no hospital 2 (p<0,0001); contudo, para fungos filamentosos potencialmente patogênicos não se encontrou diferença (p=0,7145). Durante o período de estudo, a incidência de doença fúngica invasiva por fungos filamentosos foi de 2,1% no hospital 1 e 7,6% no hospital 2. A baixa carga fúngica nos quartos do hospital 1 poderia ser explicadas pelo uso de medidas protetoras adicionais, incluindo janelas e portas fechadas, reforçando-se a importância de tais medidas no cuidados em ambientes protegidos. / Invasive fungal infections have emerged as a cause of high morbidity and mortality among patients with hematologic malignancies, especially among those undergoing hematopoietic stem cell transplantation. Fungi are ubiquitous in nature, therefore measures aimed at reducing fungal burden in hospitals have been emphasized. In this study air samples were collected in two HSCT centers in Southern Brazil, which have distinct facilities, as well diferent air control systems. All rooms of hospital 2 are equipped with HEPA filters. In addition, patients hospitalized in this unit are at a higher risk for invasive fungal diseases. A total of 130 samples were obtained during December 2009 to January 2011 from rooms, restrooms and corridors. For analysis, all fungi belonging to the genus Aspergillus, Rhizopus and Fusarium were considered filamentous fungi potentially pathogenic, while others were considered environmental fungi. The comparison between corridors of hospital 1 and 2 showed no difference in fungal concentration (p=0.114 for environmental fungi and p=0.622 for potentially pathogenic). The rooms of both hospitals showed a significant lower concentration in PPF, as compared to corridors (p<0.0001). Comparing rooms of hospital 1 e 2 there was a lower amount of environmental fungi in hospital 2 (p<0.0001) – however no difference was observed for potentially pathogenic (p=0.714). During the period of study, the incidence of invasive mold infection was 2.1% in hospital 1 and 7.6% in hospital 2. The low fungal burden in rooms in hospital 1 may be explained by the implementation of additional protective measures, emphasizing the importance of such measures in protected environments.

Dans les installations nucléaires, les particules en suspension sont le vecteur d’une grande partie de la contamination radiologique. Pour cette raison, l'IRSN (Institut de Radioprotection et de Sûreté Nucléaire) étudie les filtres THE (Très Haute Efficacité) plissés qui sont l'un des dispositifs permettant assurer la sécurité de l'exploitation nucléaire. Pour éviter les rejets dans l'environnement, la compréhension du comportement des filtres en particulier dans la situation accidentelle doit être aussi exhaustive que possible. L'accident le plus probable et le plus pénalisant pour les dispositifs de confinement est l’incendie qui conduit à une production massive de particules de suie. Dans ce cas, le colmatage des filtres est un problème qui doit être pris en compte. Jusqu'à présent, une corrélation empirique a été développée pour prédire l'augmentation de perte de charge. Toutefois, le caractère empirique de cette corrélation ne permet pas son utilisation dans toutes les situations. Une compréhension phénoménologique et un modèle de colmatage est alors nécessaire. Le travail de thèse qui suit vise à lier l'évolution de la perte de charge à des observations physiques pour chaque étape du colmatage. Pour ce faire, l'étude a été divisée en deux parties. La première se focalise sur le comportement du filtre plan en mesurant la pénétration de particules à l'intérieur du medium et la porosité du dépôt formé sur sa surface. La deuxième partie consiste en une expérience à petite échelle basée sur un seul pli. L'accumulation de particules à l'intérieur du pli a été directement observée, de plus, la déformation du pli ainsi que les écoulements d'air dans le pli (en utilisant une méthode de PIV) ont été mesurés. Au cours de ces expériences, la perte de charge a été mesurée et les paramètres mesurés ont été liés à l'évolution de la perte de charge. La finalité est de construire un modèle analytique simple afin de prédire l'évolution de la perte de charge des filtres en fonction de la masse déposée, des caractéristiques de l'aérosol et des conditions aérauliques. La principale perspective ouverte par ces résultats est la validation des modèles numériques complets pour surmonter les limites expérimentales. Le prolongement logique de ce travail sera l'étude du comportement d'un filtre colmaté soumis à des contraintes de température, d’humidité et aux agressions chimiques de produits de combustion / In nuclear facilities, airborne particles are the vector of most of the radiological contamination. For this reason, pleated HEPA filters are one of the containment devices which are actively studied by the IRSN (Institut de Radioprotection et de Sûreté Nucléaire) to ensure the safety of nuclear exploitation. To avoid contamination of the environment, the understanding of the behavior of the filters especially in accidental situation has to be as exhaustive as possible. The most probable accident and the most penalizing for the containment devices is fire which leads to a massive soot particle production. In this case, the clogging of the filters is a problematic which has to be taken into account. Up to now, an empirical correlation has been developed to predict the pressure drop increase. The empirical nature of this correlation doesn’t allow its use in all situations. A phenomenological understanding and model of the clogging is then necessary. The following PhD work aims to reduce the pressure drop evolution to physical observations for each step of the clogging in order to model it on the most physical basis as possible. To do so, the study has been divided in two parts. The first one focusing on the behavior of flat filter by measuring the penetration of particles inside the medium and the porosity of the deposit formed on its surface. In the second part a small scale experiment based on a single pleat has been developed. Accumulation of the particles inside the pleat has been directly observed, deformation of the pleat as well as airflow in the pleat (using a PIV method) has been measured. During these experiments, pressure drop has been monitored and the measured parameters have been linked to the pressure drop evolution. Finality is to build a simple analytical model to predict the pressure drop evolution of the filters as a function of the deposited mass, the aerosol characteristics and the ventilation conditions. The main perspective opened by these results is the validation of complete numerical models to overcome the experimental limits. The logical extension of this work will be the study of the interaction of a clogged filter with temperature, air moisture and chemical aggression

No description available.

The Institute of Clean Energy Technology (ICET) at Mississippi State University was awarded a contract by the DOE to design, fabricate, assemble, and characterize a research grade test stand to assist in the development of ASME AG-1 Section FI Metal Media Filters. The major barriers to completing the code section is development of a test stand for collecting data necessary to specify performance requirements for use and for filter qualification. Currently there is not a test stand capable of performing this testing. Performance criteria for the FI test stand were developed by the Section FI project team and ICET. These performance criteria were used to create a test stand to collect the data necessary to get Section FI balloted and approved.

A unique accelerated aging chamber for experimentally determining the life of nuclear grade high efficiency particulate air (HEPA) filters was designed, implemented, and characterized. A design document was developed under the Nuclear Quality Assurance program (NQA-1). The aging process is achieved by sustaining an elevated humidity condition inside the chamber for an extended period of time. Elevated humidity conditions expose the media to commonly occurring stressors that mimic the degradation a typical filter in practical applications would experience. The aged media may then be analyzed using autopsy methodology resulting in data that can be used to better understand the useful life of HEPA filters. The chamber allows age studies to be conducted in a fraction of the time. The industry requires a more complete understanding of the useful life of HEPA filters as opposed to the rule of thumb which states to dispose filters 10 years after the manufacture date.

Air filters are routinely used to remove various aerosols ranging from radioactive particles to airborne viruses. The overall performance of a filter may be simplified to consider only two main performance characteristics: 1) the efficiency at which particles are removed by the filter, and 2) the filter’s resistance to air flow. Per the DOE Nuclear Air Cleaning Handbook, HEPA filters require a minimum filter efficiency of 99.97% for particles 0.3 micrometers in diameter. Understanding how filters will perform with respect to time and mass loading is essential towards building more robust filters that operate more efficiently and safely. Analyzing the mechanics of the filter media will provide better direction towards design improvement by exploring the relationship between the pressure drop and loaded particle mass. This work summarizes the design, construction, and characterization of a testing apparatus intended to perform penetration and loading testing on various test medias with selected aerosols.

Denna rapport presenterar en utvärdering av en centrifugal luftrenare från företaget Airission som användes i en infektionsavdelning på Karolinska Universitetssjukhuset. Airissions luftrenare rensar bort partiklar och aerosoler, genom så kallad centrifugalteknologi, en relativt oprövad teknologi för luftrening. Målet var att undersöka och försöka verifiera luftrenarens funktion och prestanda samt jämföra den med en konventionell luftrenare som använder traditionella tvåstegsfilter för att rena luft.För att utföra studien användes ett bioaerosolmätinstrument som i realtid mäter partikelnivåerna i rummet. Testerna utfördes under olika driftförhållanden och tidsintervall med luftrenare påslagen respektive avstängd. Datainsamlingen och analysen inkluderade beräkningen av medelvärdet, jämförelse av partikelnivåerna mellan de olika testfallen och beräkning av standardavvikelsen.Resultaten visade att Airissions centrifugala luftrenare fungerar väl för rening av luft från partiklar och aerosoler. Reningseffektiviteten var jämförbar med en konventionell luftrenare. Den var mer effektiv än en konventionell luftrenare utan användning av högeffektiva luftfilter, mer allmänt känt som HEPA-filter. En signifikant minskning av antalet partiklar i luften observerades medan luftrenaren var i drift. Det uppstod dock en del komplikationer vid appliceringen av HEPA-filtret, vilka kunde ha haft en negativ påverkan på båda luftrenarna. Sammanfattningsvis visar analysen att den tillämpade centrifugalteknologin hos Airissions luftrenare fungerar väl. Jämförelsen av den konventionella luftrenaren visar vissa fördelar med en luftrenare som använder centrifugal teknologi - både gällande effektivitet och kvalitet.Denna rapport bidrar till kunskapen om luftreningslösningar för att förbättra luftkvaliteten och minska spridningen av luftburna sjukdomar, framför allt i sjukhusmiljöer. Resultaten kan vara till nytta för fortsatt forskning och utveckling av mer effektiva luftrenare som i sin tur ger ett bättre skydd för patienter och sjukhuspersonal som exponeras för luftburna smittämnen. / This report presents an evaluation of a centrifugal air purifier from the company Airission used in an infectious ward at Karolinska University Hospital. Airission's air purifier removes particles and aerosols using centrifugal technology, a relatively untested technology for air purification. The goal was to investigate and attempt to verify the functionality and performance of the air purifier and compare it to a conventional air purifier that uses traditional two-stage filters for air purification.To conduct the study, a bioaerosol measuring instrument was used to measure real-time particle levels in the room. The tests were performed under different operating conditions and time intervals with the air purifier turned on and off. Data collection and analysis included calculating the mean values, comparing the particle levels between different test cases, and calculating the standard deviation.The results showed that Airission's centrifugal air purifier effectively purifies air from particles and aerosols. The purification efficiency was comparable to a conventional air purifier. It was more effective than a conventional air purifier without the use of highefficiency air filters, commonly known as HEPA filters. A significant reduction in the number of particles in the air was observed while the air purifier was in operation. However, some complications arose during the application of the HEPA filter, which could have had a negative impact on both air purifiers.In summary, the analysis demonstrates that the applied centrifugal technology in Airission's air purifier works well. The comparison with the conventional air purifier shows certain advantages of an air purifier that uses centrifugal technology - in terms of both efficiency and quality.This report contributes to the knowledge of air purification solutions to improve air quality and reduce the spread of airborne diseases, especially in hospital environments. The results can be useful for further research and development of more effective air purifiers, which in turn provide better protection for patients and hospital staff exposed to airborne pathogens.

Les filtres plissés à Très Haute Efficacité (THE) sont utilisés pour le maintien du confinement des substances radioactives dans les installations nucléaires ; ils constituent ainsi un des éléments sensibles de la sûreté nucléaire. Certains scénarios accidentels, comme l’apparition d’une brèche sur une tuyauterie avec relâchement de vapeur, peuvent conduire à une forte augmentation de l’humidité relative de l’effluent gazeux filtré. Ces travaux permettent de pallier le manque de données analytiques dans la littérature concernant le comportement des filtres plissés THE, en termes de variations de leur perte de charge et de leur efficacité, en cas d’exposition à un débit d’air humide non saturé. Des expériences de colmatage de filtres ont été réalisées sur un banc d’essais à l’aide de deux aérosols : un aérosol non-hygroscopique micronique d’alumine et un aérosol hygroscopique submicronique de chlorure de sodium. Les résultats ont mis en évidence que l’influence de l’humidité durant le colmatage d’un filtre THE dépend de plusieurs paramètres : la géométrie du filtre (plane ou plissée), la granulométrie et la nature hygroscopique de l’aérosol de colmatage et enfin, le temps d’interaction entre l’aérosol et l’air humide. Des mesures d’efficacité des filtres plissés vierges et à différents degrés de colmatage, réalisées avec l’aérosol normalisé d’uranine, se sont également révélées sensibles à la présence plus ou moins importante d’humidité relative dans l’air. Enfin, l’ensemble des résultats a permis d’élaborer une approche empirique d’estimation de l’évolution de la perte de charge d’un filtre THE ; le modèle qui en résulte est applicable durant la formation sous humidité d’un gâteau de particules sans réduction de la surface de filtration / Pleated High Efficiency Particulate Air (HEPA) filters are used for maintaining the containment of radioactive substances in nuclear plants; thus, they are sensitive elements of nuclear safety. Some accidental situations, such as the emergence of a hole on a pipe with release of steam, can lead to a high increase of the air humidity. This work can overcome the lack of analytical data in the literature regarding the behaviour of pleated HEPA filters, in terms of changes in pressure drop and efficiency, in presence of humidity (unsaturated air). Experimental clogging tests have been performed on a test bench with two aerosols: non-hygroscopic micronic alumina particles and hygroscopic submicronic sodium chloride particles. The results showed that the influence of humidity during the clogging of a HEPA filter depends on several parameters: the geometry of the filter (plane or pleated), the size distribution and hygroscopicity of the aerosol clogging and finally the interaction time between the aerosol and humid air. Measurements of efficiency of clean and clogged filters (at different degrees of clogging), performed with the normalized soda fluorescein aerosol, are also sensitive to the presence of more or less relative humidity in the air. Finally, all results helped to develop an empirical model for estimating the evolution of the pressure drop of HEPA filters; this model is applicable during the formation of the particulate cake in presence of humidity without reducing of the surface area filtration