Performance Comparison of Real-Time Light Scattering Dust Monitors Across Dust Types and Humidity Levels

Abstract

Video techniques for monitoring exposure, such as NIOSH’s “Helmet-CAM,” employ both real-time dust monitors and mobile video cameras to assess workers’ respirable dust exposures. Many real-time personally worn dust monitors utilize light scattering sensing elements, which are subject to measurement biases as a function of dust type (size, composition, shape factor) and environmental conditions such as relative humidity. These biased and inaccurate dust measurements impair the monitor’s ability to properly represent actual respirable dust concentrations. In the testing described, instrument mass concentration data was collected using three different types of commonly used commercial off-the-shelf personal dust monitors and compared to a reference standard. This testing was performed in a calm air (Marple) dust chamber in which three units of each make and model (for a total of nine monitors) were used for each test. Equivalency factors (EF, a multiplier to match the Thermo TEOM 1400a reference instrument) ranged between 0.746 and 1.879 across all dusts and environmental conditions tested, and between 0.821 and 1.519 on the ISO test dust.

PM2.5 Concentration and Composition in Subway Systems in the Northeastern United States

“…In the present study, we compared real-time and gravimetric PM 2:5 concentrations during simultaneous 30-to 60min sampling sessions conducted in the targeted subway systems (except MTA-NYC or the LIRR) and found, overall, that gravimetric values were 2 4 times greater than what was measured with the real-time light scattering device. This ratio is much higher than what has been reported for other environments and dust types (Wu et al 2005;Wang et al 2016Wang et al , 2018Patts et al 2019), and this difference is most likely due to the large (e.g., as high as 60% of the total PM 2:5 mass) contribution of iron, a dense metal, to the airborne PM 2:5 in the targeted subway systems. Therefore, we adjusted our real-time PM 2:5 data with a correction factor.…”

“…2005 ; Wang et al. 2016 , 2018 ; Patts et al. 2019 ), and this difference is most likely due to the large (e.g., as high as 60% of the total mass) contribution of iron, a dense metal, to the airborne in the targeted subway systems.…”

Review of Respirable Coal Mine Dust Characterization for Mass Concentration, Size Distribution and Chemical Composition

“…Different types of low-cost direct-reading dust monitors have been developed to supplement the regulatory required mass-based CMDPSU and CPDM. Many of these monitors are photometers that use the principle of light scattering by an ensemble of particles to infer mass concentration [46,[50][51][52]]. As for the example shown in Figure 2c, a photometer draws particle laden air through a cyclone to achieve the desired size cut.…”

Occupational exposure to respirable crystalline silica among US metal and nonmetal miners, 2000–2019

“…Obtaining serial (multiple, over time) exposure measurements for individual workers provides an opportunity to observe temporal patterns in the worker's exposure, between‐worker exposure variability, an indicator of variable work practices, and better estimation of workers' cumulative exposure risk. For example, utilizing dust assessment tools such as the NIOSH‐developed Helmet‐Cam respirable dust exposure assessment technology, in which mine workers are instructed to wear a real‐time aerosol monitor (in a backpack, safety belt, or safety vest) and a video recorder on their hardhat, can help mine operators analyze dust exposure data in a timely and more detailed manner to better identify the specific tasks, processes and work areas with elevated exposures 43,44 . It is understood that at some sites workers may perform multiple tasks within (or outside of) their primary job description.…”

“…To that end, the importance of frequent monitoring using noncompliance tools such as the rapid quartz monitors (also known as "end-of-shift" monitors) 42 exposure data in a timely and more detailed manner to better identify the specific tasks, processes and work areas with elevated exposures. 43,44 It is understood that at some sites workers may perform multiple tasks within (or outside of) their primary job description. For work settings where miners perform a series of disparate tasks each shift, it is important to determine the specific tasks and length of time workers conduct each task to establish relevant task-based control strategies.…”