Air measurements

AH closed loop control systems must measure the amount of air needed under all conditions of engine demand. Air measurement is most often done using a hot wire anemometer, usually referred to as a mass air meter (99,100). 

An existing eontrol arrangement uses a PID eontroller to eontrol the temperature of the proeess air (measured by thermoeouples) and the dry elay moisture eontent measured by samples taken by the works laboratory. If this is out of speeifieation, then the proeess air temperature is raised or lowered. The dry elay moisture eontent ean be measured by an infrared absorption analyser, but on its own, this is eonsid-ered to be too noisy and unreliable. 

Rubber fume in air measured as Lab method using filters and 47/2... 

SI I97I/I6I Clean Air (Measurement of Grit and Dust from Eurnaces) Regulations... 

The ineident eommander may rely on visual observation of plae-ards, labels, and manifests and information gathered during the response. Obtaining air measurements with monitoring equipment for toxie eon-eentrations of vapors, partieulates, explosive potential, and the possibility of radiation exposure is important for determining the nature, degree, and extent of the hazards [2]. 

Air quality The concentration of one or more pollutants in the air, measured in either ppm or pg m . It may be related to pollution sources inside an enclosure or outdoor air. Temperature and moisture conditions may also be considered. 

Atmospheric dust concentration The dust burden present in atmospheric air measured in mg m ... 

Flame speed The speed of a flame burning through a flammable mixture of gas and air measured relative to a fixed observer, that is, the sum of the burning and translational velocities of the unbumed gases. 

Assume that a plant air system requires 10,000 fti/min of dry air measured at 14.7 psia and 60°F. The air is required at 100 psia. Intake conditions are... 

MDHS47 Rubber fumes in air, measured as total particles and cyclohexane soluble material . 

The major drawback to using the Florida study to support the correlation between indoor and soil measurements was that the indoor measurements were obtained from 3-day closed-house charcoal measurements, and soil radon was obtained from 1-month alpha track measurements buried 1 ft beneath the soil surface. Comparisons of charcoal and alpha track data are generally not recommended since they are quite different measurement techniques, and represent radon levels over different time periods. However, the study was subjected to numerous quality control checks including deployment of alpha track detectors in 10% of the houses to obtain a check on indoor air measurements made by charcoal canisters. In spite of the measurement drawbacks, the study indicates that soil radon measurements taken alone are not a dependable predictor of potential indoor radon concentration. 

Rubber fumes in air, measured as total particles and cyclohexane soluble material . Newspaper print rooms measurement of total particulates and cyclohexane soluble material in air. 

In the granite and alum shale areas, exhalation measurements above the ground were well correlated with the indoor air measurements. In the esker area, the exhalation rates were normal, and the high indoor Rn-222 concentrations here are believed to be caused by convective flew due to underpresure in the houses. (Stranden et al, 1985). 

Fig. 5.6 Pressure dependence of thermal conductivity of air, measured using a PDDA coated microsphere of effective radius 298 pm. The fit to (5.11), shown as the curve, gives a thermal accommodation coefficient of 0.92 for air on PDDA. Reprinted from Ref. 5 with permission. 2008 International Society for Optical Engineering...

FIGURE 3.12 Impedance curves of LSCF ad LSCF/GDC composite cathodes in air measured at different temperatures. (From Hwang, H.J. et al., J. Power Sources, 145 243-248, 2005. With permission.)... 

The perception of odour is due to the presence of volatile compounds in the inhaled air. Measurement of this perception can be carried out directly by psychophysical methods or indirectly by analysing the air for the odorous volatile compounds. Both methods however present a number of limitations and difficulties. 

These iodometric calibration methods are based on the assumption that there is a stoichiometric reaction between ozone and the iodine in the various potassium iodide procedures. Three essentially independent methods have been used to test the accuracy of this assumption measuring the absorption of ultraviolet radiation at 254 nm by ozone in air, measuring the absorption of infrared radiation at 9,480 nm by ozone in air, and determining the ozone concentration in air by titration with nitric oxide. 

Only one report of human death attributed to 1,4-dichlorobenzene exposure has been located in the literature. A 60-year-old man and his wife died within months of each other due to acute yellow atrophy of the liver (also known as massive hepatic necrosis or fulminant hepatitis) (Cotter 1953). Their home had been "saturated" with 1,4-dichlorobenzene mothball vapor for a period of about 3-4 months, but no air measurements were available. Clinical symptoms included severe headache, diarrhea, numbness, clumsiness, slurred speech, weight loss (50 pounds in 3 months in the case of the husband), and jaundice. The wife died within a year of the initial exposure however, it was not clear if 1,4-dichlorobenzene was the primary cause of death. This case study did not address whether these individuals consumed excessive amounts of alcohol or had previous medical problems, such as a chronic liver infection. 

The concentration of element i (mass per unit volume of air) measured at a receptor site is related to the source contributions by... 

Implications for Source Studies. The results discussed above Indicate the need for measurements of a number of elements In studies of particles both from sources and In ambient air. Measurements of Na, Pb, Ca, As, Mn and V are very Important for use In receptor models. Aluminum and Fe are quite useful, but not essential If many other llthophlle elements are measured (e.g., SI, Tl, Sc). Likewise, Zn Is useful, but could be replaced by elements such as Sb and Cd. However, AI, Fe and Zn can usually be measured more easily than their surrogates. Iron and elements such as Cr, Mn, Co and N1 will be Important In areas that have Iron and steel Industries and elements such as Cu, Zn, Pb and other chalcophlles In areas that have non-ferrous metal Industries. Sources of the unexplained Mn, Cr, Cu, Nl, K and Mg In Washington need to be Identified. Thus, we have a set of about 15 elements that should be measured as a minimum, plus others that may provide additional useful Information, e.g., Br, Ba, Cd, Sb. Note that It Is not sufficient to measure a given element only In particles from the dominant source of the element. For example, motor vehicles are the major source of Pb In most areas however, significant amounts are released by refuse Incinerators and non-ferrous smelters. Thus, If the CEB Is to determine the correct source strength for the motor—vehicle component, Pb contributions from the other, less Important sources must be known. 

Infrared spectroscopy has been applied to ambient air measurements since the mid-1950s (Stephens, 1958). Indeed, PAN was first identified in laboratory systems by its infrared absorptions and dubbed compound X because its identity was not known (Stephens et al., 1956a, 1956b). It was subsequently measured in ambient air (Scott et al., 1957). Since then, IR has been applied in many areas and has provided unequivocal and artifact-free measurements of a number of compounds. Because of its specificity, it has often been used as a standard for intercomparison studies (e.g., for HNO see later). 

Other infrared absorption techniques are also used in ambient air measurements, including tunable diode laser spectroscopy (TDLS), nondispersive infrared (NDIR) spectroscopy, and matrix isolation spectroscopy. These are discussed in more detail later. 

A problem in the application of FTIR to ambient air is that water vapor, C02, and CH4 are all present in significant concentrations and absorb strongly in certain regions of the spectrum. As a result, the spectral regions that are useful for ambient air measurements are 760- to 1300-cm-1, 2000- to 2230-cm-1, and 2390-to 3000-cm l. 

As discussed with respect to the measurement of individual compounds, different coatings are used for the collection and measurement of different compounds. The criteria used to choose these coatings and interferences that can occur in the application of denuders to ambient air measurements are discussed by Perrino et al. (1990). 

There are some methods that are specific to HCHO. For example, the Hantzsch reaction of HCHO, collected with a diffusion scrubber, with ammonium acetate, acetic acid, and acetylacetone to form diacetyldihydrolutidine, which is measured using its fluorescence at 470 nm, has been applied to air measurements (Dasgupta et al., 1988, 1990 Kleindienst et al., 1988a,b Lawson et al., 1990 Khare et al., 1997). Reaction with 1,3-cyclohexanedione and ammonium acetate to form a dihydropyridine derivative that is measured by fluorescence has been used in conjunction with a diffusion scrubber (Fan and Dasgupta, 1994). Enzymatic methods have been used in which formaldehyde dehydrogenase catalyzes the oxidation of HCHO to HCOOH in the presence of -nicotinamide adenine dinucleotide, NAD+, which is reduced to NADH. The latter is measured by fluorescence at 450 nm (Lazrus et al., 1988 Ho and Richards, 1990). 

In another intercomparison using TDLS, several DNPH methods, the 1,3-cyclohexanedione diffusion scrubber, and the enzymatic method were compared using both spiked samples and ambient air. The TDLS was used as a standard for comparison. For ambient air measurements, results obtained with the 1,3-cyclohexanedione diffusion scrubber were about 30% higher than those obtained with TDLS, whereas results for the enzymatic method were about 35% lower. The DNPH cartridge measurements were quite variable, which may... 

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