Background: Current standards and procedures for parametric load release are based on technologies from the 1960s, are consensus based and are often not supported by scientific evidence. In the literature, however, methods are reported which can fairly easily be implemented and improve current parametric load release for steam sterilization.Aim: To implement an improved parametric load release procedure, exceeding the current standards and methods for monitoring steam sterilization processes. Implementation of the procedure should be feasible for all interested end-users.Method: The steam sterilization criteria specified in the literature were used to define a set of steam sterilization conditions. A search for commercially available devices and methods which can assess these conditions parametrically was performed. After selecting a method, a field study was carried out.Findings: Two devices were identified which could be used to improve parametric load release after a steam sterilization process. A comparison showed that a permanently installed device which -independent from the sterilizer -measures the temperature, the steam composition in the chamber and the time for every steam sterilization process, offers the most advantages. The selected method has been implemented and tested on 51 steam sterilizers. Conclusion: The selected method makes steam sterilization safer, more sustainable, and more cost effective. It can be implemented by all interested end-users.(c) 2023 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

In practice it is claimed that load characteristics influence a surface steam sterilization process. To the best of our knowledge, no information on this topic has been found in the literature. The purpose of this study was to find if a load influences the duration and related characteristics of a surface steam sterilization process. In a case study, every load monitoring using an objective, quantifying steam penetration test was performed during 30 days. This resulted in 98 production processes with load monitoring. The acquired data were analyzed. A relation between the weight of a load and the duration of a surface steam sterilization process has been found. In this case study, it is demonstrated that the process time increases with the weight of the sterilizer load. Additionally, it is concluded that when the duration of a process is longer, diffusion will have a greater effect and steam penetration increases.LAY ABSTRACT: Steam sterilization is applied in most health-care facilities that reprocess medical devices, in pharmaceutical industries, and in labs where specific instrumentation and equipment have to be sterile. Steam sterilization is still not fully understood, as demonstrated in the literature. Our manuscript contributes to understanding the surface steam sterilization process. The information shared in our manuscript demonstrates by a case study that relations exist between the weight of the load which is steam sterilized, the duration of a process, and the steam penetration in a process. A quantitative relation can be used to predict the duration of a process and the steam penetration. It is likely that for other steam sterilizers these relations can be found as well. This is of interest for institutes researching decontamination and sterilization, health-care facilities, developers and manufacturers of medical devices, and committees addressing standards for steam sterilization.

The most commonly applied method to sterilize re-usable medical devices in hospitals is steam sterilization. The essential conditions for steam sterilization are derived from sterilization in water. Microbiological experiments in aqueous solutions have been used to calculate various time–temperature combinations to kill viable micro-organisms [ [1] Perkins J.J. Principles and methods of sterilization. Charles C Thomas, Springfield1956 Google Scholar ]. In principle, similar conditions can be realized by the presence of condensate of steam. The Medical Research Council (MRC) adapted the time–temperature combinations of Perkins [ [1] Perkins J.J. Principles and methods of sterilization. Charles C Thomas, Springfield1956 Google Scholar ] for steam sterilization, but added 'a further (safety) period' [ [2] Working Party on Pressure Steam Sterilizers of the Medical Research Council Sterilisation by steam under increased pressure. Lancet. 1959; 273: 425-435 Abstract Scopus (11) Google Scholar ] to allow for 'deviations in steam quality'.

Sodium sulfate is known as one of the most destructive salts causing weathering. Many experiments on accelerated weathering tests show that major deterioration effects by weathering are caused by drying and wetting cycles of porous materials saturated with salt solution. In this study we have performed accelerated weathering tests with sodium sulfate in common building materials (fired-clay brick, Indiana limestone and Cordova limestone) measuring the concentration in the materials simultaneously with their expansion. The concentration of sodium sulfate solution is measured non-destructively using Nuclear Magnetic Resonance, while the expansion of the sample caused by crystal growth is measured with a fiber optic displacement sensor. The simultaneous measurement of solution concentration within a material and expansion allow assessment of crystallization pathways most responsible for damage during weathering, i.e., cycles of wetting and drying. It was shown by direct observation, that with rewetting of the partially dried samples, the present thenardite experiences a rapid partial transformation to decahydrate. Simultaneously with this transformation a rapid expansion of the sample was measured in situ.

A set-up especially designed for semi-simultaneous measurements of 1H, 23Na and 35Cl in ordinary cementitious materials using nuclear magnetic resonance was built. This setup makes use of the main field of a whole body magnetic resonance imaging system (Philips Intera), which has allowed us to combine two measurement setups into one, i.e., a 23Na/35Cl and a 1H insert. This 1.5 T field was chosen as a compromise between the signal-to-noise ratio of the spin-echo signal, which increases at higher frequencies, and the line broadening due to the presence of magnetic impurities of these materials, which leads to a decrease of the resolution at higher magnetic fields. The preliminary experiments show that this setup can be used to the study the interaction of different types of ions with cementitious materials. One-dimensional profiles of the moisture and dissolved ions can be measured with a spatial resolution of about 2 mm for 1H, 6 mm for 23Na and 9 mm for 35Cl.

The use of crystallization inhibitors has been proposed as a potential preventive treatment method against damage and is extensively tested for crystallization of single salts. However, in practice salt mixtures are present. Therefore, before using inhibitors in practice there is a strong need to explore their effect on salt mixtures. In this research, we studied the effect of ferrocyanide ions ([Fe(CN)6]4−) on NaCl crystallization in single salt and in salt mixtures of NaCl–KCl and NaCl–LiCl. A series of micro droplet drying experiments were undertaken. Time lapse microscopy of the crystallization was performed along with NMR measurements of hydrogen, sodium and lithium ions. This gives the possibility to visualize the drying of the droplet while simultaneously obtaining information of both NaCl and LiCl concentration in the droplet. For a NaCl solution droplet, in the presence of inhibitor, a significantly higher supersaturation prior to the onset of crystallization and a change in crystal morphology were observed. On the other hand, for salt mixtures, lower supersaturation compared to single salt and dendritic crystal morphology was seen in the presence of inhibitor. In a porous material, such a type of morphology can promote the formation of efflorescence that causes only little structural damage.

Sodium sulfate is known as one of the most destructive salts leading to the deterioration of porous materials, such as monuments, sculptures, and civil engineering structures. While sodium sulfate crystals are growing in a porous material, crystallization pressure will build up. In this study we have combined a nondestructive measurement of the concentration of the pore solution within a material by using NMR with an optical measurement of the expansion of the material during crystallization. These data permit calculation of the in-pore crystallization pressure during the growth of different crystalline phases induced by cooling in three different materials: fired-clay brick, Cordova Cream limestone, and Indiana limestone.

In dental offices, steam sterilisation is used to sterilise instruments and in that way to prevent the cross-contamination of patients and the dental team. In order to ensure that the sterilisation process has been executed successfully, every sterilisation process has to be monitored. The monitoring of every load in the steam steriliser is necessary and often even required, either directly (by legislation) or indirectly (by harmonised standards). The complete monitoring protocol consists of controls of the installation, the exposure, the loading, the packaging and, finally, the 'track and trace' of the instruments. For examining the installation, a steam penetration test, such as the Bowie and Dick test, can be carried out.

Salts are widely recognized as a cause of deterioration of porous building materials. A general approach to slow down salt damage problems is reducing the salt content of the affected object. One of the most common treatments is the application of poultices. Desalination by poultices may result from two different salt transport processes: diffusion and advection. In this study we consider only the advection process. In the case of advection based desalination the efficiency of salt extraction strongly depends on the pore-size range of the substrate and the poultice. For advection to be effective, the poultice materials should be adapted to the pore-size distribution of the substrate. However, the poultice can shrink during drying, which affects the pore-size distribution of the poultice material. The salt transport from the poultice to the substrate by water advection results from a capillary pressure gradient, but upon drying a salt concentration gradient may appear in the poultice/substrate interface. Because of this concentration gradient an osmotic pressure arises, which may change the drying behavior of the poultice/substrate system. We have investigated the effect of the pore size distribution of the poultice and the osmotic pressure on the drying behavior of a poultice/substrate system. To this end, we have measured the time evolution of moisture and salt concentration profiles in a system consisting of kaolin/sand poultice on a fired-clay brick, using a specialized NMR setup. Comparison of the results with a model based on capillary pressure equilibrium at the poultice/substrate interface shows that the accumulation of salt from the substrate in the poultice may improve the salt extraction process, because the osmotic pressure decreases the effective pore size of the poultice. (C) 2013 Elsevier Ltd. All rights reserved.

Repeated cycles of crystallization and dissolution of the salt crystals inside the pores of a building material can provoke damage to that material. To find effective treatment methods against this damage, a better understanding of the crystallization process is required. For this purpose, a microscopic study on a sodium chloride (NaCl) solution droplet is performed. The crystallization behavior of NaCl during repeated crystallization and dissolution cycles is studied using time lapse microscopy along with Nuclear Magnetic Resonance (NMR). Using NMR non-destructive and simultaneous measurements of hydrogen and dissolved sodium ions were made. The results show that with repeated cycles the number of available foreign nucleation sites for salt crystallization decreases. The resulting decrease of the number of crystals leads to an increase in crystal size. A maximum supersaturation up to 1.16 +/- +/- 0.08 was observed. (C) 2014 Elsevier B.V. All rights reserved.

Static 1H NMR Free Induction Decay (FID) signals of polymer solids contain a lot of information about the molecular dynamics. A T2 analysis of the FID has generally been performed in terms of discrete two- or three-component models. However, this requires a priori assumption of the number of proton species before analysis. This paper presents a method of analyzing the FIDs of the polymer solid samples in terms of a continuous T2 distribution. A mixed Gaussian and Exponential kernel function was used to represent the true characteristic of FIDs of the polymer solids. A simple and realistic assumption has been made to reduce the number of degrees of freedom in the continuum fitting and to make the fitting stable. An experimental static 1H NMR FID of a typical polymer solid sample was analyzed as an example in the end to demonstrate the application of this method.

In surgery medical devices are used that should be sterile. To obtain surface steam sterilization conditions in hollow medical devices (e.g. endoscopes), sufficient water vapour should be present in the narrow channels in these devices during sterilization. In this paper, a model to calculate the water vapour distribution in narrow channels during steam sterilization processes is presented. The narrow channels in the devices are modelled as tubes with one open and one closed end. The model is restricted to isothermal situations in which no condensation takes place. To validate the model, the time evolution of the water vapour density at the closed end of a test tube is quantified by a pilot experiment based on infrared light absorption measurements. A stainless-steel test tube was used with a length of 54 cm, a radius of 1.5 mm and a wall thickness of 0.5 mm. These dimensions are comparable to the channels in medical instruments. Both the model calculations and the experiments show that for a wide range of sterilization process parameters the vapour density near the closed end of the tube is insufficient for steam sterilization. Despite the simplicity of the model, a fair overall agreement is found between the model predictions and the experimental results. This agreement can be improved significantly by an empirical modification of the boundary conditions at the open end of the tube. Our calculations show that the tube length is the most important parameter. Some possible changes in the process parameters to increase the water vapour concentration at the closed end of the tube are addressed briefly.

The crystallization of salts is widely recognized as one of the most significant causes of irreversible damage to many cultural objects such as wall paintings, stone sculptures, historic buildings. The removal of salts from these objects is however difficult and often poultices are used. In these methods a wet poultice is applied to the surface of the substrate to be treated and is kept in place for some period of time before being removed. Many studies up to now on poulticing have focused on the salt and moisture transport solely in terms of advection and diffusion. The objective of this study is to demonstrate the potential contribution of osmotic pressure to salt extraction during poulticing treatments. To this end we have conducted a series of experiments where we have measured the moisture and salt transport during poulticing for some well defined materials. Here we have used nuclear magnetic resonance to measure non-destructively the moisture and ion transport during these experiments. This study shows that osmotic pressure can exert a significant influence on salt extraction by poulticing methods during drying. Importantly, as salt is transported from the substrate and into the poultice, this results in a build-up of osmotic pressure within the poultice decreasing the effective pore-size of the poultice. Therefore the build-up of osmotic pressure enhances the salt extraction and thus increases the efficiency of the poulticing treatment.

In surgery, medical devices that are used should be sterilized. To obtain surface steam sterilization conditions, not only in the sterilizer chamber itself but also in the loads to be sterilized, the amount of non-condensable gases (NCGs), for instance air, should be very low. Even rather small fractions of NCGs (below 1%) seriously hamper steam penetration in porous materials or devices with hollow channels (e.g., endoscopes). A recently developed instrument which might detect the presence of residual NCGs in a reliable and reproducible way is the 3M(TM) Electronic Test System (ETS). In this paper, a physical model is presented that describes the behavior of this instrument. This model has been validated by experiments in which known fractions of NCGs were introduced in a sterilizer chamber in which an ETS was placed. Despite several approximations made in the model, a good agreement is found between the model predictions and the experimental results. The basic principle of the ETS, measuring the heat transfer by condensation on a cooled surface, permits a very sensitive detection of NCGs in harsh environments like water vapor at high temperatures and pressures. Our model may serve to develop adapted and optimized versions of this instrument for use outside the field of sterilization, e.g., in heat exchangers based on steam condensation.

The microstructure of a polymer coating plays an important role in the water uptake behavior. This paper aims to correlate the molecular mobility and the water-polymer interactions with the microstructures of a highly cross-linked PU system. GARfield NMR imaging was used to monitor in situ the water uptake of the PU coating at different temperatures. The results of continuum T-2 fitting show that at temperatures below the enthalpy relaxation temperature (65 degrees C) the PU coating uptakes water, whereas the polymer matrix is not plasticized by the presence of water. At higher temperatures, however, the polymer matrix is significantly mobilized by the presence of water molecules as indicated by the appearance of the longer T-2 component. The water content in the PU coating is monitored by GARfield NMR at different temperatures. The results show that the water content decreases in two steps as the temperature decreases from 85 degrees C to the room temperature. This result is explained in combination with the molecular relaxation phenomenon probed by the DSC. A microstructure model was formulated based on the experimental results.

In dental offices steam sterilization is used to prevent infection of staff and patient. The necessity of sterilization is obvious. To ensure effective sterilization processes each load has to be monitored. Based on literature and standards a state of the art concept of every load monitoring is described.

In dental offices steam sterilization is used to prevent infection of staff and patient. The necessity of sterilization is obvious. To ensure effective sterilization processes each load has to be monitored. Based on literature and standards a state of the art concept of every load monitoring is described.

High spatial resolution NMR imaging techniques have been developed recently to measure the spatial inhomogeneity of a polymer coating film. However, the substrates of the polymer coatings for such experiments are generally required to be non-metallic, because metals can interact with static magnetic fields B0 and RF fields B1 giving rise to artifacts in NMR images. In this paper we present a systematic study on the effects of metallic substrates on 1D profiles obtained by high resolution NMR imaging. The off-resonance effect is discussed in detail in terms of the excitation profile of the RF pulses. We quantitatively show how the NMR signal intensities change with frequency offset at different RF pulse lengths. The complete NMR profiles were simulated using a Finite Element Analysis method by fully considering the inhomogeneities in both B1 and B0. The excellent agreement between the calculated and measured NMR profiles on both metallic and non-metallic substrates indicates that the experimental NMR profiles can be reproduced very well by numerical simulations. The metallic substrates can disturb the RF field of the coil by eddy current effect and therefore change the NMR profiles. To quantitatively interpret the NMR profile of a polymer layer on a metallic substrate, the profile has to be divided by the profile of a reference on the same metallic substrate located at the same distance from the coil.

Nuclear magnetic resonance (NMR) is used to non-destructively measure the moisture and dehydration profiles in gypsum during one sided heating to temperatures of 400 degrees C reflecting the conditions during fire. The temperature and moisture profiles are recorded simultaneously. The gypsum used in the experiments was extensively characterised using TGA, DSC, MIP, and NMR. The influence of the initial moisture content on the drying and dehydration processes was tested by varying the moisture content of the samples: capillary saturated, 50% RH, and 0% RH.By calibrating the NMR signal with moisture content we have shown that it is possible to not only measure free or absorbed water with NMR, but also measure the degree of hydration of the gypsum. Furthermore, by comparing the NMR signal decays it is possible to distinguish between these two water populations. The measured water profiles reveal that during one sided heating of a gypsum sample the dehydration inside is taking place in a two-step reaction. Furthermore, the profiles indicate that the vapour produce by the dehydration reactions condensates and thereby increases the local moisture content. The condensated water forms a so-called moisture peak behind the dehydration front.To our knowledge the measurements described in this article are the first quantitative in-situ evidence for the existence of two dehydration fronts in gypsum during one sided heating. Furthermore, the built up of a moisture peak in gypsum behind the dehydration front has not been reported in the literature to our knowledge. The NMR heating experiments presented in this paper can be used to evaluate and validate hygro-thermal models in the field of fire research on building materials. (C) 2011 Elsevier Ltd. All rights reserved.

This article presents the first non destructive measurements of salt ions transport through fired-clay brick during electrokinetic desalination using nuclear magnetic resonance technique. The effect of the strength of an applied electric field on the migration of salt ions is examined by varying the electrical potential gradients from 0.75–2 V cm−1 across the specimens. The measurements show that for electrokinetic to exceed ion transport by diffusion a minimum level of applied voltage is necessary. Below this threshold salt transport by diffusion is dominant over electromigration. The effect of advection on the salt transport is studied by introducing a hydraulic gradient across the specimen. The results show that advection is a major transport process in the materials studied. To assess the relative magnitude of the various active transport processes during electrokinetic desalination, a scale analysis on the basis of dimensionless numbers is presented. The value of these numbers determines which transport mechanism will dominate the desalination process in a given sample length and time scale.