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Biomedical subjects

T H Meltzer

Publications and source records attributed to T H Meltzer.

7 recordsLinked to original sources
PubMed1979

New filter compositions for the analysis of airborne particulate and trace metals.

Characteristics are presented of various new filter materials of polyvinyl chloride--polyacrylonitrile, polyimide, polyaromatic, and of quartz fibers. These filters have been specifically developed for air sampling applications. Included in the presentation are comparative performance characteristics such as: infrared and ultraviolet spectra, inorganic and trace metals analyses, chemical compatibilities and reactivities with various liquids and gases, moisture pick-up, mass per unit area, mechanical properties (tensile strength and elongations), air flows/pressure drops, and particle retention efficiencies. Examples are presented of the increased acceptance of membrane filters in air analyses due to their simplifying tedious conventional procedures and their improvement of sensitivity, precision, and accuracies. Included are the ability of specific synthetic filters to impart optical transparency for analyses of asbestos and other fibers by transmission techniques using oil immersion or dispersion staining, the direct determination of silica on an acrylonitrile membrane by infrared, the direct determination of atmospheric particulate types and the concentrations of each. Other examples given are trace metal analyses by X-ray fluorescence, and gravimetric procedures and scanning electron microscopy techniques for analyses of suspended particulate matter.

Acrylonitrile↗
PubMedDate not supplied

The insufficiency of single point diffusive air flow integrity testing.

Filter manufacturers characterize a given filter type by a single acceptable maximum diffusive air flow level. A too high value is prudently rejected as signalling the possible presence of flaws. Values lower than the stipulated maximum are accepted. However, the presence of single pores, whatever their sizes, is not being revealed. Only their influence within the total porosity is measured by the diffusive air flow. Single point diffusive air flow integrity testing may invite misleading conclusions because it offers possibilities for lower air flows to mask the presence of flaws or of outsized pores. This is particularly so where initial (prefiltration) and final integrity are being compared. The filtrative accretion of retained material, viable or not, must inevitably come to block or diminish the size of the pores. This results in decreased total porosity, directly expressed in lower diffusive air flow values. Sufficient drop in such final air flow values may mask the presence of a flaw developed in the filter subsequent to its initial testing. For this reason a filter's entire air flow permeation curve, particularly including its bubble point, must be characterized. It is this measurement, and this measurement alone, that is capable of unambiguously revealing the existence of insufficiently retentive pores. The inquiry into such presence is the very purpose of filter integrity testing.

Air Movements↗