Continuous air sampling

Continuous air sampling (monitoring) for health and safety purposes is the responsibility of the ISP (Inspected State Party). For real-time monitoring over a short period, the IT has the option to use handheld detectors triggering an alarm if contamination levels exceed a certain concentration. In case of... 

Continuous air sampling in the vicinity of the Rocky Flats facility near Denver was initiated in 1970. The data in Table 5-1 are from locations 50 meters, 1 kilometer, and 2.5 km from the facility and are arithmetic means of data from sampling years 1970 to 1976. For purposes of comparison, sampling data for New York City for the same time interval are included. Data from all four locations indicated declining levels following 1971 (Volchok et al. 1977). 

In polar ice sheets air gets continuously trapped, and ice cores obtained by drilling through the ice caps therefore constitute a continuous set of ancient air samples. 39Ar/Ar and 81Kr/Kr measurements on these samples primarily reflect the production rates of these radioisotopes averaged over a few half-lives. 

Air-sampling detector Actively and continuously samples the air from a protected space and is able to sense the pre-combustion stages of incipient fire. 

Comprehensive two-dimensional GC (GC x GC) has been applied to the analysis of many complicated systems including petroleum and air samples (Ryan and Marriott, 2003). This technique is more powerful than previously developed heart-cutting methods, in which a small section of eluent from one column is injected onto a second for further separation (Ryan and Marriott, 2003). In GC x GC, two columns with fundamentally different separation mechanisms are cormected by a modulator (O Figure 1-2). The modulator continuously refocuses portions of the eluent from the first column onto the second column. The... 

Before 1970, most of the data for nitrogen oxides were obtained by continuous measurements with a colorimetric analyzer that was similar in principle to the colorimetric oxidant analyzer shown in Figure 6-8. The scrubbing agent is a mixture of -(l-naphthyl)ethylenediamine, sulfanilic acid, and acetic acid in aqueous solution. The color is produced when both nitrogen dioxide and nitrites react with this reagent to form an azo dye. The color is not affected by nitric oxide in the air sample. 

Intersociety Committee. Tentative method for continuous monitoring of atmospheric oxidant with amperometric instruments, pp. 341-350. In Methods of Air Sampling and Analysis. Washington, D.C. American Public Health Association, 1972. 

This theory was tested by Yoffe(Ref 1) by comparing the energies required to initiate NG and PETN with and without entrapped air. Samples prepared without air in the form of a continuous Rim requited much higher energies of initiation than samples with entrapped air. A simple method of including a gas phase in an expl is to spread it as a small annulus on a flat anvil. When this is struck with a flat hammer, the small amt of gas in the center is trapped and compressed. In these experiments the size of the annulus was such that the initial vol of the gas was ca 5 x 10"4 cc. A more detailed description of the theory of adiabatic compression and methods of testing are gi ven in Ref 2... 

Packed column technology has been used in airborne gas chromatographs for the separation and quantitation of sulfur species (46, 47) and peroxyacetic nitric anhydride (48). The combination of sample preconcentration and sensitive detectors has yielded detection limits that are superior to corresponding continuous sensors. For S02, a detection limit of 25 pptrv was claimed, and for peroxyacetic nitric anhydride the detection limit was roughly 60 pptrv for an 50-cm3 air sample. Analysis times for samples were on the order of 10 min. 

Continuous Sampling and Determination. There are no truly continuous techniques for the direct determination of sulfuric acid or other strong acid species in atmospheric aerosols. The closest candidate method is a further modification of the sensitivity-enhanced, flame photometric detector, in which two detectors are used, one with a room-temperature de-nuder and one with a denuder tube heated to about 120 °C. Sulfuric acid is potentially determined as the difference between the two channels. In fact, a device based on this approach did not perform well in ambient air sampling (Tanner and Springston, unpublished data, 1990). Even with the SF6-doped H.2 fuel gas for enhanced sensitivity, the limit of detection is unsuitably high (5 xg/m3 or greater) because of the difficulty in calibrating the two separate FPD channels with aerosol sulfates. 

A number of specialty companies have and are continuing to develop adsorbents to collect organic molecules from air samples. Industrial chemicals resulting, from syntheses or used in production processes, pesticides and emissions from exhaust towers are monitored routinely with commercially available adsorbents. Personnel monitoring can be accomplished without a pump using a system composed of a porous membrane through which air diffuses and compounds of interest are collected by an adsorbent. 

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