Filterability, measurement

Filter measured volume of air through lead-acetate-impregenated filter paper tape compare optical density with unexposed impregnated spot of similar area. Lead-acetate-impregnated filter paper tape No data NR EPA 1978... 

Tumble dryers use pressure sensors for filter measurements by measuring the differential pressure across the lint filter signalling the user when to clean the filter. 

Moosniuller, H., W. P. Arnott, C. F. Rogers, J. C. Chow, C. A. Frazier, L. E. Sherman, and D. L. Dietrich, "Photoacoustic and Filter Measurements Related to Aerosol Light Absorption during the Northern Front Range Air Quality Study (Colorado 1996 1997), J. Geophys. Res., 103, 28149-28157 (1998). 

Figure 3.55 Chebyshev low pass filter, measured data.

Figure 3.60 Chebyshev high pass filter measured results.

Calibration is time consuming when performed correctly. It may require 1 or 2 days to perform all the necessary steps (i.e., prepare stocks, filter, measure absorbance, check purity, dilute, mix, and inject calibrants). Once the stock solutions and mixed calibration solutions have been prepared, a calibration check can be performed in -4 hr. Sample preparation, depending on the matrix, may require a few minutes or a few hours. If an autosampler is unavailable for overnight injection the extracts are typically stable overnight, refrigerated at - 20° to 4°C. It is prudent to maintain the autosampler tray temperature from 4° to 15°C to reduce sample degradation. HPLC analysis of the extracted sample requires 20 to 60 min. Typically one technician can extract 12 to 24 samples per day to be analyzed overnight or the next day. 

Percent chrysotile asbestos in bulk samples may be measured by X-ray powder diffraction (NIOSH Method 9000, 1984) sample dust grinded under liquid N2 wet sieved through 10-mm sieve sieved material treated with 2-propanol agitated in an ultrasonic bath filtered on a silver filter measured by XRD, using a Cu target X-ray tube. 

The dye laser irradiates an external cell which contains 40 Pa (0.3 torr) Io vapor. A 1P28 photomultiplier whose face is covered by a 610 nm long pass filter measures the 12 fluorescence, while a photodiode monitors a reflected spot of the dye laser. The ratio of fluorescence to dye laser power is displayed on a strip chart recorder. The si dearm temperature is gradually (1-2 hours) raised from about 210 K or 220 K, where fluorescence in the external cell is strong, to whatever temperature is required to reduce the signal by about 60%. 

Wolf, T. and H. Bittermann (1997). Determination of adsorption parameters of active carbon filters measuring only the beginning of the breakthrough curve. SAE Special Publications Automotive Climate Control Design Elements, Proc. 1997 Int. Cong. Exposition Feb. 24—27, Detroit, MI, 1239, 51-54. SAE, Warrendale, PA. 

The naturally occurring radioisotopes that were measured, Be and Pb, continue to be detected in most air filter samples. Variations in the annual mean concentrations of Be at many of the sites appear to result primarily from changes in the atmospheric production rate of this cosmogenic radionuclide. Short-term variations in the concentrations of Be and °Pb continued to be observed at many sites at which weekly air filter samples were analyzed. These short-term fluctuations probably resulted from variations in meteorological factors. The data from quality control samples indicate that in general the reliability of the air filter measurements are acceptable for their intended application. 

The VESUVIO measurement was repeated with a U filter, where the MC simulation indicated that the effects of the CA were negligible. The results of the Au and U filter measurements are also shown in Fig. 8. It can be seen that the difference between the data with the two filters is consistent with the MC calculation, with an offset of the values obtained from the different filters, but that the slope of the experimental curve is unchanged. Furthermore the size of the observed anomaly is much larger than the systematic errors introduced by the CA for both Au and U filters. 

Measure the average face velocity of each terminal HEPA filter. Measure the average velocity 1 ft above the workspace, exposed product areas, or exposed component areas in all Class 100 laminar flow rooms or areas. 

Filtering. For control variables, when filtering is needed, use a first-order filter to reduce the effects of high-frequency noise. Do not excessively filter measurements unless absolutely necessary. The filter time constant, x, should be much less than feedback dynamics. 

Figure 2. Dependence of the observed rate of reprotonation on the two-dimensional concentration of pyranine anion in the hydration layer. The rate constant (y) was calculated from the experiments carried out as in Figure 1. The concentration of the anion was calculated from the amplitude of the transient and the dye-lipid ratio of the preparation. The magnitude of the amplitude was varied by modulation of the excitation pulse energy by glass filters. Measurements were carried out in the absence of sucrose, A, and in the presence of 0.57-M sucrose (1.5 X 107 dyn/cm2), B.

IF a micron filter measures 2 feet long by 2 feet high by 6 inches deep and has a static pressure rating of 1,0 inches of resistance, the fan required would have to be capable of pushing 400 CFM at 1 inch of static pressure. 

Figure 4 Cartoon depicting technique for quantification of nebulizer output and measurement of deposition. On the left, a patient inhales nebulized particles via a Y piece. The exhalation filter captures exhaled particles. On the right, the same patient performs a similar maneuver. The inhaled mass filter captures particles that would have been inhaled. Differences between filters measure deposition. Breathing pattern can be monitored using a pneumotachograph represents the sum of minute ventilation plus nebulizer flow leaving the expiratory arm of the Y piece). (From Ref. 9.)...

The filter measures inhaled mass. In the insert is a sketch of the filter configuration used to measure exhaled particles (and hence deposition) and a gamma camera for regional studies. 

The simultaneous analysis of concentration and composition in GPC measurements is of significant interest for today s complex polyolefin copolymers. The same IR detector can be used to analyze ethylene-vinyl acetate (EVA) or other functional polyolefin copolymers (with a carbonyl group) as a function of molar mass. All that is needed is to replace the methyl interference filter by a carbonyl region filter. An example of a maleic anhydride-modified PE is shown in Fig. 9, with an IR interference filter measuring at 1,740 cm . ... 

This type of detector is frequently used in pesticide-residue analysis because of its high specificity and selectivity and its high sensitivity to sulphur and phosphorus compounds. In the arrangement devised by Brody and Cheney the radiation from a hydrogen-air flame is directed to a photomultiplier through an interference filter. Measurements are taken... 

In a study conducted at Chandigarh by Bandhu et al. (2000), Aerosol samples were collected on 0.8 pore size using cellulose nitrate filter, were mounted on Millipore aerosol standard filter holder. The air through the filter paper sucked with the help of Millipore diapharagmatic vacuum pump. Sixteen elements namely S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, and Pb have been detected. The air around Chandigarh is found to contain relatively more concentration of Fe, Ca, and Ti and very small amount of Ni and Cu. The typical spectra from aerosol sample along with the spectrum from blank filter measured by the PIXE and EDXRF are as shown in Figs. 1.29 and 1.30. 

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