Documents sampling instruments 3 results

"The NIOSH Analytical Method 7400 for airborne fibers specifies the use of electrically conductive cowls for air sampling. Data collected from a number of laboratories indicate that a significant fraction of collected dust may be deposited on the inside of electrically conductive cowls during air sampling for man-made mineral fibers. The purpose of this article is to present a cowl rinsing procedure for airborne fiber sampling. This method is the consensus of an ad hoc group formed to evaluate existing cowl rinsing procedures. A number of issues related to cowl rinsing are also addressed."

"National Institute for Occupational Safety and Health Method 7400 is commonly used to evaluate airborne exposures to man-made mineral fibers (MMMFs). Although recent evidence suggests that current methods for collecting air samples may be biased due to fiber deposition on the inside of the sampling-cassette extension cowl, few data are available on the mechanism of deposition, the number of fibers deposited on the cowl, or potential bias in size selection associated with this deposition. The length and diameter distributions of fiber populations collected on the air-sample filters were compared to those deposited on the inside of the electrically conductive extension cowl. The samples were collected during insulation of residential buildings with pneumatically conveyed loose-fill insulation. Two different filters recommended for sample collection in the World Health Organization Reference Method for MMMFs were used. It was determined that a significantly different fiber-size distribution is derived from analysis of fibers collected on the air-sample filter versus fibers deposited on the extension cowl. In general, fibers deposited on the inside of the extension cowl were longer and thicker than fibers from the air-sample collection filter."