Test atmosphere

Instruments based on this principle may be calibrated by a two-step process shown in Fig. 14-2 (4). A test atmosphere with a known source of... 

Generation of test atmospheres of organic vapours by the syringe injection technique Generation of test atmospheres of organic vapours by the permeation tube method On-site validation of sampling methods... 

MDHS 3 Generation of test atmospheres of organic vapours by the syringe injection technique... 

O. Nelson, "Controlled Test Atmospheres, Principles and Techniques" Ann Arbor Science Publishers, Ann Arbor, MI, 197i. 

The detector used to measure indoor radon was the latest version of the passive activated carbon device developed at EML (George, 1984 Warner, 1986), which consists of a thin-walled aluminum canister with a screen cover to expose 80 g of carbon to the test atmosphere. Although not as physically rugged as earlier models, properly packed this monitoring device was as successful in conducting the surveys through the mail. 

Melcher RG, Borders RA, Coyne LB. 1986. Development and validation of personal monitoring methods for low levels of acrylonitrile in workplace atmosphere I. Test atmosphere generation and solvent desorption methods. Am Ind Hyg Assoc J 47 152-157. 

Influence of Testing Atmosphere on Anode Electrochemical Performance... 

Zwart et al. (1990) exposed groups of five male and five female Wistar rats to phosgene at varying concentrations for 5, 10, 30, or 60 min. The test atmosphere was monitored at both the inlet and outlet of the glass exposure chambers by gas chromatography and infrared analysis. The 10-min LC50 value was 80 ppm, and the 30-and 60-min LC50 values were 20 and 12 ppm, respectively. 

Data Adequacy Although human data are limited to primarily occupational monitoring studies, the data base on animal studies is good. The test atmosphere in the key study was supplied via a face mask to the restrained test subjects restrained animals have been shown to be more sensitive than unrestrained animals to inhaled toxicants. Relative species sensitivity to inhaled HCN may be related to breathing rate. Compared to rodents, the slower breathing rate of humans and monkeys may make them less sensitive to the effects of HCN. 

The concentration of the test atmosphere must be reasonably uniform throughout the chamber and should increase and decrease at a rate close to theoretical at the start or end of the exposure. Silver (1946) showed that the time taken for a chamber to reach a point of equilibrium was proportional to the flow rate of atmosphere passing through the chamber and the chamber volume. From this, the concentration-time relationship dining the run-up and run-down phase could be expressed by the equation... 

The chamber or exposure manifold materials should not affect the chemical or physical nature of the test atmosphere. 

Nelson, G.O. (1980). Controlled Test Atmospheres. Ann Arbor Science, Ann Arbor. 

Examples of such procedures are making dilutions (not all components of the mixture may be equally soluble or miscible with the vehicle) and generating either vapors or respirable aerosols (not all the components may have equivalent volatility or surface tension, leading to a test atmosphere that contains only a portion of the components of the mixture). 

Acute inhalation toxicity To determine the potential acute toxicity-lethality following a single 4-h inhalation exposure to a test atmosphere containing the new pharmaceutical excipient (aerosol, vapor or particles)... 

As the test showed, the formation of the hydroxide carbonate and the speed at which this takes place are dependent on the composition of the test atmosphere, especially on the water pressure. The zinc oxide did not show any weight gain in a C02 atmosphere with a moisture ratio (p/p0) less than 0.1 i.e., no formation of hydroxide carbonate takes place. Only above a moisture ratio of 0.35 did the zinc oxide take up more water in a relatively short period of time than was necessary for the formation of basic zinc carbonate. In the moisture ratio range of 0.1—0.3, the formation was slower and did not lead to complete formation of hydroxide carbonate. 

Aufderheide et al. [84] performed experiments with human lung cells that were directly exposed to diesel exhaust. In contrast to other exposure concepts for complex mixtures, this experimental setup facilitates a direct and reproducible contact between the cell monolayer and the test atmosphere. This could be achieved by following improvements (i) a strict separation of the medium... 

RL SOP No. 70-3, dated June 1, 1967, describes methods used at Edgewood for searching for and selecting toxic chemicals. Some of the details In connection with exposure of human volunteers to experimental irritant chemicals are described. Human volunteers were exposed to compounds after review of animal screening data and approval by committees based on a conclusion that the experimental chemicals were safe for human use. Generally, two volunteers were exposed to each substance. Subjects were exposed in a wind tunnel at an airspeed of 5 mph and were asked to resist leaving the test atmosphere (up to 1 min) until exposure was unbearable. 

Brorson T, Skarping G, Renman L, et al. 1989. Test atmospheres of diisocyanates with special reference to controlled exposure of humans. Int Arch Occup Environ Health 61(8) 495-501. 

A detailed protocol for laboratory validation of sampling and analytical methods for toxic substances in workplace environments is given in Figure 1. The literature was searched and a method of sampling and analysis was selected. The next step was to evaluate and, if necessary, develop an analytical method that was compatible with the sampling medium. If a satisfactory analytical method became available only then did we undertake generation of a test atmosphere. Then samples were collected with the appropriate collection medium. Both capacity and collection efficiency were evaluated. 

When insufficient data are available, it may be necessary to generate test atmospheres to determine the physical state of a compound and the collection efficiency of a filter and vapor collector. The estimation of the vapor/particulate ratio may also depend on concentration and sample loading. For example, in a short sampling time, vapor may be efficiently collected on a filter, but longer term sampling may reveal saturation of the filter with vapor and eventual passage of the vapor into a backup bubbler or sorbent tube. 

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