Thermally induced filter bias in TEOM mass measurement
Abstract
Researchers at the National Institute for Occupational Safety and Health (NIOSH) have long used stationary tapered element oscillating microbalances (TEOMs®) in laboratory settings. They have served to assess the mass concentration of laboratory-generated particulates in experimental dust chambers and they provide a reference method for comparison with other particulate-measuring instruments. Current NIOSH research is focused on further adapting TEOM technology as a wearable personal dust monitor (PDM) for coal mining occupations. This investigation’s goal is to help identify, quantify, and provide means for resolving certain TEOM-related error. The present research investigated bias caused by thermal effects on filter assemblies. New filters used in the PDM for 8 h tests show an average positive bias of 25.5 μg, while similar tests of equivalent filters used in two 1400A model TEOMs show an average positive bias of 34.3 μg. The derived bias values allow correction of previously collected biased data. Also, pre-heating the filters for 24 h at 46 °C shows significant bias