Gas sampling bags

Araki A, Noguchi T, Kato F, et al Improved method for mutagenicity testing of gaseous compounds by using a gas sampling bag. Mutat Res 307(l) 335-44, 1994... 

Several calibration procedures were attempted before a suitable procedure was found. When aliquots of vinyl acetate in hexane were injected directly into the hot desorbing oven, erratic results were obtained. This was probably due to reaction of vinyl acetate on the hot metal surface of the desorbing oven. Another procedure tested used gas sampling bags filled with known concentrations of vinyl acetate in helium. 

The second method has the same characteristics, except for the calibration table. Since the injection pressure when using gas sampling bags is lower, the response decreases and, therefore a new calibration table has to be prepared, mainly due to the non linear nature of the hydrogen calibration curve. 

Gas samples were collected in Tedlar gas sample bags and analyzed for their content of CO, C02, H-, CL, and total hydrocarbons using the process analyzer described lh Cw Moisture content of the gas was determined by the condensation method (15). 

A second topology for vapor delivery to sensor devices entails preparing the desired air/vapor mixture in a flexible gas sample bag and then drawing the gas past the sensor head by a vacuum pump placed downstream of the sensor (Fig. 7.8). The air/vapor mixture is simply prepared by adding a... 

Fig. 7.8. Flow cell arrangement for challenging sensor devices with air/vapor mixtures prepared in Tedlar gas sample bags...

In addition, we have begun more rigorous testing of the OSC sensors using the vacuum-driven pull method. A preliminary experiment is described here. A gas-tight fluoropolymer flow cell was constructed with approximately 300 ml internal volume as shown in Fig. 7.10. Tedlar gas sample bags were used to prepare vapor concentrations of interest and the air/vapor mixtures were... 

Besides charcoal, methods using passive dosimeters, gas sampling bags, impingers, and detector tubes have been utilized for determination of EtO exposure. In addition, there are several commercially available portable gas analyzers and monitoring units. 

C. Tedlar Gas Sampling Bags-Samples are collected by drawing a known volume of air into a Tedlar gas sampling bag. The ethylene oxide concentration is often determined on-site using a portable gas chromatograph or portable infrared spectrometer. 

Gas collectors A sampling bag used to collect a sample for analysis. 

Hcxanc can be determined in biological fluids and tissues and breath using a variety of analytical methods. Representative methods are summarized in Table 6-1. Most methods utilize gas chromatographic (GC) techniques for determination of -hexane. The three methods used for preparation of biological fluids and tissues for analysis are solvent extraction, direct aqueous injection, and headspace extraction. Breath samples are usually collected on adsorbent traps or in sampling bags or canisters prior to analysis by GC. 

In order to prevent condensations, an equipment is used, dynamically allowing the dilution of a known flow of the odorous gas in a known flow of an inodorous gas the temperature of the dilution gas must be that of the gas to be diluted if it is a hot gas ideally a heat exchanger should be set as much upstream the olfactometer (or sampling bag) as possible. 

The largest problem turned out to be the temperature differences between outlet air (85-220 C) and outdoor temperatures (0-15 C), causing condensation. The dew point of the outlet air was calculated, and experiments were carried out with dilution of the outlet air to prevent condensation in the sampling bags. Condensation was prevented by diluting the outlet air 5-150 times with diy, purified N2 gas. 

The TO 6 type got two separate gas jet pumps, one for each measuring range and an el. magn valve. A range selector does the same as the flow selector of the modified TO 4 type. The second stream is lead to an additional sniffing port which can be used by the panel leader. A port selector brings the main stream to one of four sniffing ports (masks), installed in four separate boxes. This equipment has been set up in a caravan. To set it vertical it is mounted to a ball and socket. Four panelists can take place in front of their masks A sample bag can directly be connected to the olfactometer. The delay between... 

The caravan is equiped with an own propan gas operated electric power unit and the ventilation system is equiped with activated carbon filters to get an odourless athmosphere guaranteed. After arriving at a farm it takes less than five minutes to prepare the system for the first measurement. With a team of four well-trained panelists and three repetitions it takes only about six minutes per sample. Inclusive necessary breaks for the panelists and for changing the sample bags six measurements per hour are possible, but not more than about 20 samples per day. 

The second approach laboratory analysis of air and/or soil samples (note the air sample can be obtained by gas samphng bag, filter, sorbent, and wet-contaminant collection methods). 

Two final examples of the sensitivity and general applicability of the FTIR gas analysis technique are illustrated in Fig. 8. Trace (A) shows the spectrum obtained from an ultra-air filled 70 liter sampling bag into which had been injected, 18 hours previously, 4.8 microliters of TDI, toluene diisocyanate. On the basis of the single feature at 2273 cm l, it is estimated that 50 ppb TDI could be detected. The lower Trace (B), shows the spectrum of nickel carbonyl. This highly toxic but unstable gas was found to decay rapidly at ppm concentrations in ultra air (50% lifetime 15 minutes). Calibration of its spectrum was established by recording successive spectra at ten minute intervals and by attributing the increase in carbon monoxide concentration (calibration known) to an equivalent but four times slower decrease in nickel carbonyl concentration. The spectrum shown represents 0.6 ppm of the material. Note the extraordinary absorption strength. The detection limit is thus less than 10 ppb. 

In static method a known amount of contaminant is introduced into a fixed volume of air in devices such as teflon bags, gas sampling bulbs and gas cylinders, etc. Dynamic methods involve continuous introduction of contaminant (at a controlled rate) into a stream of air. Static methods are generally much simpler to construct and use, however, these suffer from a number of problems. Dynamic methods, while more elaborate and relatively more expensive, offer greater flexibility in concentration range, sample volume and are also less affected by adsorption losses. 

The total gas sample during an experiment, usually between 100 and 200 liters, was collected in a bag made from a roll of Polythene tubing sealed at each end and fitted with an inlet nozzle. The Polythene tube, when lying flat, was 1 ft. wide, and when it was filled with 100 liters of gas at atmospheric pressure, it produced a cylindrical bag about 10 ft. long. Only a very small pressure difference was required between the inside and the outside of the bag for filling and emptying. 

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