Gas Delivery Systems Research Articles

Hazards of anesthesia gas delivery systems

Hazards of anesthesia gas delivery systems

Contamination control in gas delivery systems for MOCVD

Each of the elements of a gas distribution system potentially is a source of contamination in film growth reactors. A detailed technical understanding of the origin and properties of the most common contaminants, their fluctuations and their interaction with the different elements in the delivery system are essential to provide consistent high gas purity for device growth. Governing processes in the gas source, the delivery system, and purifiers were addressed with selected examples, along with approaches for integrated solutions. The examples include impurity fluctuation in NH 3 as a function of the method of delivery, moisture outgassing from particle filters as a function of filter material and matrix gas, and low-level breakthrough in packed bed adsorbent-based purifiers as a result of transport and reaction rate limitations.

NON-PHYSICIAN ASSISTED SUICIDE: THE TECHNOLOGICAL IMPERATIVE OF THE DEATHING COUNTERCULTURE

This article reports on the 2nd Self-Deliverance New Technology Conference (NuTech), held in November 1999, in Seattle,Washington. Right-to-die activists from six countries met to demonstrate a number of devices for non-medical assisted death and to share preliminary findings on their use. The author attended all sessions of the private conference and received confidential memoranda and papers. An overt observer-as-participant method was used. Five devices for non-medical assisted death were demonstrated. These included three systems for breathing inert gas, a customized plastic bag for asphyxiation called the Exit Bag, and a closed circuit breathing system called the Debreather. Seven deaths out of eight trials were reported for the Debreather and four deaths were reported using the Exit Bag. Additionally, a non-quantified number of deaths using inert gas delivery systems were described by various conference delegates. The systems demonstrated by the NuTech group are designed to induce death quickly and painlessly. In general, they leave negligible, if any, post-mortem evidence of their use.The compulsion to use technology to cause death, the "technological imperative," has emerged as part of underground care of dying persons. This imperative raises serious challenges to the health care professions, legislators, and policy makers, particularly because it has led to a sophisticated, expanding movement of non-medical death providers.

NON-PHYSICIAN ASSISTED SUICIDE: THE TECHNOLOGICAL IMPERATIVE OF THE DEATHING COUNTERCULTURE

This article reports on the 2nd Self-Deliverance New Technology Conference (NuTech), held in November 1999, in Seattle,Washington. Right-to-die activists from six countries met to demonstrate a number of devices for non-medical assisted death and to share preliminary findings on their use. The author attended all sessions of the private conference and received confidential memoranda and papers. An overt observer-as-participant method was used. Five devices for non-medical assisted death were demonstrated. These included three systems for breathing inert gas, a customized plastic bag for asphyxiation called the Exit Bag, and a closed circuit breathing system called the Debreather. Seven deaths out of eight trials were reported for the Debreather and four deaths were reported using the Exit Bag. Additionally, a non-quantified number of deaths using inert gas delivery systems were described by various conference delegates. The systems demonstrated by the NuTech group are designed to induce death quickly and painlessly. In general, they leave negligible, if any, post-mortem evidence of their use.The compulsion to use technology to cause death, the "technological imperative," has emerged as part of underground care of dying persons. This imperative raises serious challenges to the health care professions, legislators, and policy makers, particularly because it has led to a sophisticated, expanding movement of non-medical death providers.

Evaluating Individual Risk in the Operation of Gas-Delivery Systems for the Gas-Flame Processing of Materials

Evaluating Individual Risk in the Operation of Gas-Delivery Systems for the Gas-Flame Processing of Materials

Medical gas delivery systems. Activity report of the local commission for surveillance of gas delivery at the University Hospital of Nancy

Local commissions for the surveillance of medical gas supply systems were made compulsory in France in 1985. This article analyses the activity of the local commission of the University hospital of Nancy. Main anomalies which occurred in the pipeline network, especially tightness problems, are discussed. Difficulties concerning the planning and the course of the visits of the gas supply systems by the commission are analysed. Finally, the actual power and responsibility of the commission members are considered.

Exposure of Inert Gas Purifiers to Air: Studies on Hydrocarbon Release in Resin-Based vs. Nickel-Based Purifiers

Gas purification is an integral part of many semiconductor manufacturing processes. Accidental air contamination into gas delivery systems can lead to adverse consequences. This paper addresses the use of inorganic nickel-based purifiers versus organomentallic resin-based purifiers in the event of air intrusion. Tests were performed under conditions that simulate a large purging error. Both purifier technologies undergo reaction exotherms. Hydrocarbon oil release, which results in catastrophic system contamination, occurs with organometallic resin purifiers. For nickel-based purifiers, system contamination is limited to air breakthrough.

Moisture Drydown in Ultra-High-Purity Oxygen Systems

Semiconductor manufacturing fabs use ultra-high-purity (UHP) oxygen for various process applications such as oxide growth, plasma etch, and chemical vapor deposition. Moisture is identified as one of the key impurities that can affect device production. Moisture drydown in inert gas delivery systems was studied extensively. However, moisture drydown or outgassing characteristics in oxygen were found to be different from those of inert gas systems. Moisture adsorption and desorption in UHP oxygen systems were studied using advanced APIMS techniques for trace-level moisture analysis. To understand moisture reaction pathways, isotopic water was used as an adsorbate on 316L electropolished stainless steel (EPSS) surfaces. Experimental results from moisture drydown in the EPSS tubing were used to validate a theoretical model developed to predict the moisture drydown performance of large-scale, oxygen distribution systems. Both experimental and model results were shown to be useful in UHP oxygen system design, cost control, metrology, and contamination control.

Highly reliable fitting for gas delivery systems

After confirming the basic characteristics of two types of metal gasket fittings, which are used in construction of ultrapure gas delivery systems for semiconductor manufacturing, it is noticed that the pipe usually twists at the time the fitting is tightened. This may be the possible cause of an external leak, therefore a twist leak test was undertaken to confirm the reliability of the seal during assembly. As a result, it was found that one type of fitting leaked and another type of fitting did not leak. This later type did not leak (leak rate is less than 2.98×10−16 Pa m3/s) even after 70° of twisting.

Complications of Anesthesia Gas Delivery Systems

Complications of Anesthesia Gas Delivery Systems

Contamination issues in gas delivery for semiconductor processing

The contamination contribution from two functionally similar gas delivery systems supplying a process tool is quantified in this investigation. The conventional gas delivery system consists of single-melt stainless steel tubing (/spl sim/20 Ra), elastomer components, and the ultraclean gas delivery system consists of double-melt stainless steel (/spl sim/5 Ra), all metal components. Moisture, oxygen, and hydrocarbon impurities desorbing from the wetted surfaces of the gas delivery system are analyzed using an atmospheric pressure ionization mass spectrometer (APIMS). Particle contamination from components in the gas delivery system is characterized with a condensation nucleus counter (CNC) using static and dynamic testing. Corrosion-induced particulate occurring in the heat-affected-zone (HAZ) near welded portions in tubing is also studied. The moisture contribution of the conventional gas delivery system is a factor of six greater than that from the ultraclean gas delivery system and the oxygen contamination is a factor of three greater. The particle shedding (0.01 /spl mu/m) in the static mode from the conventional manifold is 20 times greater than that from the ultraclean manifold. The HAZ of the conventional weldment shows aggressive corrosion-induced particulate and loss of the electropolished surface compared to the HAZ of the ultraclean weldment. The effect of the choice of material, components and manufacturing techniques is correlated to the extent of contamination contributed by the gas delivery system.

A numerical model of an intensive care ventilator-humidifier system

Current intensive care ventilator-humidifier systems neither monitor nor adequately control inspired gas humidity. Problems of low delivered humidity and condensation within ventilator circuitry are commonly encountered. To help to address these problems, a numerical model of a complete ventilator-humidifier-patient intensive care system has been developed. The model, based on a finite difference technique, can predict pressures, flow-rates, temperatures and relative humidities at discrete points throughout the system. A comparison of numerical predictions and measurements in a real system is reported. A strong qualitative agreement is demonstrated in all cases studied, and a good quantitative agreement is obtained in most cases. It is concluded that such models could be used to assess methods of controlling ventilator-humidifier systems to prevent the occurrence of condensation. Similar models could be developed for other medical gas delivery systems.

Materials selection for HBr service

This study was undertaken to determine the compatibility of hydrogen bromide (HBr) with common materials of construction used for specialty gas delivery systems. Reactions between reactive gases and materials of construction can result in the formation of particles and volatile metal complexes as well as the creation of corrosion products that can retain water. We found that when moisture is below 1 ppm v (designated as anhydrous), bromine from HBr is not incorporated beyond the native oxide of electropolished 316L stainless steel (EP316L) and no macroscopic degradation of the metal occurs. Also, if adequate purging and evacuation procedures are followed to remove the HBr, this material can be exposed to moist air without diminishing the initial surface quality. However, if adequate precautions are not followed to eliminate water in the presence of HBr, iron-and bromine-rich crystalline deposits form on the surface. Purge and evacuation procedures are inadequate for removal of the reactive species on this surface and corrosion proceeds upon subsequent exposure to air. EP316L exposed to HBr containing 1700 ppm v H 2O appears visually unaltered, but close inspection by SEM reveals the onset of corrosion. Of the materials examined in this study, Nickel-200 and Hastelloy C-22 are more resistant to HBr corrosive environments. In contrast, deleterious reactions occur between anhydrous HBr and elemental iron and the iron-rich surface of oxygen-passivated 316L.

Trace Water Vapor Detection in Nitrogen and Corrosive Gases by FTIR Spectroscopy

A commercial Fourier transform infrared spectrometer (modified to improve the purge) and a long‐path gas cell were used to demonstrate a detection limit of about 10 ppb for water in , , and . This technology is being developed as an in‐line monitor to extend the life of gas delivery systems and improve wafer yields in the semiconductor industry. The reported detection limit includes an improvement of about a factor of three achieved by applying quantitative multivariate calibration to the problem. Methods are discussed to compensate for background moisture in the beam path. Also, discussed are the choice of operating parameters to optimize the instrumental performance. Surprisingly, resolving the narrow water absorption bands is not necessary to achieve optimal sensitivity. In fact, optimal sensitivity is achieved at 2 to 4 cm−1 resolution, allowing the use of an inexpensive interferometer in the final instrument. A calibration over the range of 40 to 2000 ppb of water in has been performed and found to be in good agreement with published spectral data. Finally, an improved instrument design is discussed which is projected to have a lower detection limit and a shorter collection time.

06 O 04 Formation and control of particles in silane gas delivery systems

06 O 04 Formation and control of particles in silane gas delivery systems

Trace Moisture Analysis in Specialty Gases

Even though we have been successful in reducing impurities, particularly moisture in bulk gases such as , Ar, and to below the 1 ppb level for semiconductor industry, the same performance has not been achieved in specialty gas delivery systems. This is due to the fact that these specialty gases are very active and corrosive, and they contain trace impurities including moisture. These gases react readily with gas delivery system surfaces and deteriorate the process equipment and performance. In order to reduce impurities in specialty gases, it is essential to improve our methods for measuring the impurity level in these gases, in particular, the residual moisture. The current techniques such as impedance‐type or crystal oscillation moisture detection systems are inadequate because these gases not only attack the system but also dissolve in adsorbed moisture on the sensor, causing the measuring conditions to change drastically, necessitating frequent cleaning and recalibration of the detector. To improve the reliability and the sensitivity of measuring the moisture level in specialty gases, we have developed a method to overcome these difficulties. The concept of the new method is quite simple. First, we pass a specialty gas of interest through tubing to allow the moisture to completely adsorb onto the tubing surface and reach the equilibrium between the gas and the solid surface. Then, we switch the gas and pass a carrier gas such as Ar through the tubing to desorb the moisture. The stripped moisture in the Ar carrier gas is then measured. We have demonstrated this method experimentally to measure the moisture level in and . We heated a piece of stainless steel tubing to 400–450°C and passed ultrahigh purity Ar containing 50 ppt moisture to completely strip off the adhered moisture from the inner surface. Next, the and gas with an unknown moisture level was introduced to the tubing system for a sufficient period of time for all the moisture to adsorb onto the surface and reach the gas and solid equilibrium. Then we switched the gas and passed an ultrahigh purity Ar carrier gas through the system to strip off the adsorbed moisture and subsequently the moisture in the carrier Ar was measured by atmospheric pressure ionization mass spectrometry by using the flow ratio of the Ar carrier gas and the gas. This new method was found to be useful to detect impurities in all specialty gases to ppb level.

The Marshall Space Flight Center Drop Tube Facility

A description of the structural and instrumentation hardware and the improved experimental capabilities of the 105-m Marshall Space Flight Center Drop Tube Facility is described. The structure comprising the Drop Tube Facility is designed to provide a high-vacuum facility in a vertical orientation. The low-gravity environment obtained during free-fall and the containerless materials processing capabilities are discussed. Two furnaces, an electron-beam and an electromagnetic levitator, are used to melt metallic samples in a process environment ranging from 10−6 Torr to 1 atm. Specifics of the vacuum control and gas delivery systems are provided. The experimental instrumentation and data acquisition systems used to perform predrop and in-flight measurements of the melting and solidification process are discussed. Typical experimental results are presented as an indicator of the performance of the Drop Tube Facility.

The upgrading and replacement of anaesthetic equipment: a provincial approach

A formal on-site survey of all anaesthetizing locations in the Province of Manitoba was initiated in the Spring of 1988. Serious deficiencies of anaesthetic equipment previously noted on random survey were confirmed. Recognizing a need for improved standards for delivery of anaesthetic services through safe, functional anaesthetic equipment, the province undertook to fund the upgrading of all anaesthetic gas delivery systems under its jurisdiction. Sixty-six hospitals were surveyed for a total of 203 anaesthetic machines (111 urban, 92 rural). One hundred and sixty-seven machines had been used at least once in the previous year. After careful assessment 92 machines were replaced, 66 machines were upgraded and 45 machines were deleted from further service. Although the maintenance and upgrading of medical equipment is the individual health care facility's responsibility, substantial benefit was recognized by a provincial approach. The authors recommend a similar approach for other Canadian provinces.

Middle cardiac nerve section alters ventilatory response to Pa CO 2 in the cockerel

To determine whether afferents in the middle cardiac nerves (MCN) contributied to extrapulmonary Pa co 2 mg/kg), and cannulated the cutaneous ulmar vein, and the carotid and brachial arteries. The thorax was opened and each lung unidirectionally ventilated from separate gas delivery systems. A ligature, which temporarily occluded blood flow, was placed around the right pulmonary artery. Both cardiac sympathetic nerves were cut, as well as the left vagus just above the level of the recurrent branch. We exposed the non-perfused right lung to 105 Torr P co 2 to silence intrapulmonary cemoreceptors (IPC). We measured blood pressure, heart rate and ventilatory movements while the denervated left lung was used to fix Pa co 2 at sevel levels ranging from 7–140 Torr. As arterial P co 2 increased, ventilatory amplitude increased from 0.3 mm to 3.6 mm, while frequency decreased from 140 to 24 per min. After cutting the MCN, ventilatory movements were less responsive to Pa co 2 changes. Ventilatory amplitude was 3.0 mm at the lowest Pa co 2 and increased to 4.0 at the highest Pa co 2 . We conclude that: 1) when IPC discharge is low, afferents in the MCN inhibit ventilatory movements during hypocapnia, and 2) these afferens may contribute to systemic CO 2 sensitivity.

Medical gas delivery systems.

Medical gas delivery systems.