Browsing by Author "L'Orange, Christian, committee member"

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Open Access
A direct-reading particle sizer (DRPS) with elemental composition analysis
(Colorado State University. Libraries, 2023) Sipich, James Robert, author; Yalin, Azer P., advisor; Volckens, John, committee member; L'Orange, Christian, committee member; Carter, Ellison, committee member
There is a lack of aerosol measurement technology capable of quantifying, in real-time, the size, concentration, and composition of large inhalable particles with an aerodynamic diameter larger than 20 µm. Aerosols of this size penetrate the upper respiratory system upon inhalation and present surface contamination hazards upon settling. The ability to obtain information on the composition of airborne particles is necessary to identify and control risks from exposure to potentially toxic materials, especially in the workplace. The objective of this work was to validate the performance of a prototype Direct-Reading Particle Sizer (DRPS) that counts and sizes particles via time-of-flight light scattering and determines single-particle elemental composition via Laser-Induced Breakdown Spectroscopy (LIBS). Counting, sizing, and spectral measurement efficiency were evaluated using test aerosols of multiple materials with diameters between 25 and 125 µm. Particle sizing results showed good agreement with optical microscopy images. The relationship between the median aerodynamic diameters measured by the DRPS time-of-flight and optical microscopy was linear (Deming regression slope of 0.998) and strongly correlated (r2 > 0.999). The mean absolute difference between the median aerodynamic diameters measured by the instrument by time-of-flight and microscopy over all 8 test aerosol types was 0.9 µm with a mean difference in interquartile range of 1.9 µm. The prototype sensor uses an optical triggering system and pulsed Nd:YAG laser to generate a microplasma and ablate falling particles. Particle composition is determined based on collected emission spectra using a real-time material classification algorithm. The accuracy of the composition determinations was validated with a set of 1480 experimental spectra from four different aerosol test materials. We have studied the effects of varying detection thresholds and find operating conditions with good agreement to truth values (F1 score ≥ 0.9). Details of the analysis method, including subtracting the spectral contribution from the air plasma, are discussed. The time-of-flight aerodynamic diameter measurement and LIBS elemental analysis capabilities demonstrated by the DRPS provide a system capable of both counting, sizing, and identifying the composition of large inhalable particles.
Open Access
Diurnal and seasonal predictability of envelope pressures driving natural infiltration in residential buildings
(Colorado State University. Libraries, 2024) Bledsoe, Dominic, author; Bond, Tami, advisor; L'Orange, Christian, committee member; Farmer, Delphine, committee member
This study examines the dynamics of residential building envelope pressures by predicting and comparing time series site-specific weather conditions at minute-level resolution. Utilizing theoretically established relationships of both stack and wind effects, this research examines the predictability and accuracy of envelope pressures under different weather conditions. When high wind effects are removed, the Mean Absolute Error (MAE) in stack pressure predictions are minimized, typically falling below 0.24 Pa. The use of airport weather data, even after correcting for height difference and terrain, was found to be inconducive to prediction, highlighting the preference for site-specific measurements to enhance prediction accuracy. This research utilizes minute-level data for real-time environmental monitoring, aiming to inform pressurization or integrate predictive models for dynamic indoor air quality management. The findings contribute to the field by offering a practical approach to measuring and predicting residential air exchange rates, providing insights that could lead to improved health outcomes and energy efficiency in homes.
Open Access
The effects of ambient air-injection on particulate matter emissions in high firepower chimney cookstoves
(Colorado State University. Libraries, 2017) Hogberg, Thor, author; Marchese, Anthony, advisor; L'Orange, Christian, committee member; Collett, Jeffrey, committee member; Jathar, Shantanu, committee member
Approximately 2.8 billion people use solid fuel to cook and heat their homes. The resulting emissions from using solid fuel to cook and heat has detrimental effects on both indoor and outdoor air quality. In 2012 it was estimated that 4.3 million premature deaths occurred from indoor air pollution and 3.7 million deaths occurred from ambient air pollution. In 2009 it was estimated that incomplete combustion and harvesting of solid biofuels combined accounted for 1.9-2.3% of all greenhouse gases and short lived climate forcers. Due to the high firepower of institutional stoves, they produce far greater amounts of particulate matter (PM) than residential cookstoves; despite this fact, they have received little attention in comparison. Technology at the Advanced Biomass Combustion Laboratory has been developed that is capable of reducing PM emissions in high firepower chimney stoves by over 90%, and shifting the elemental to organic carbon ratio (EC/OC) towards a higher organic fraction. These changes were achieved by the use of high velocity air injection directly above the combustion chamber. Air injection nozzle orifice number, diameter, and the mass flow rate of injection air was tested to understand what combination of geometry and flow rate resulted in the best overall emissions reduction. The most significant emissions reductions occurred at high velocities that resulted from nozzles with fewer and smaller holes.