Characterizing personal exposure in close proximity to indoor air pollution sources
Abstract/Contents
- Abstract
- A total of 68 experiments were conducted in two homes under natural ventilation rates ranging from 0.2 -- 5.4 air exchanges per hour, each involving 12 to 37 real-time carbon monoxide (CO) or particulate matter (PM2.5) monitors placed in proximity (0.25 -- 5.0 m) to a controlled stationary point source. Concentrations measured in close proximity (within 1 m) to the source were highly variable, with 5-min averages that typically varied by > 100-fold. This variability was due to short-duration (< 10 s) pollutant concentration peaks ("microplumes") that were frequently recorded in close proximity to the source -- for PM2.5, these peaks often exceeded 1000 ug/m3. Compared with concentrations predicted assuming uniform, instantaneous mixing within the room, average concentrations measured within 0.25 m of the source were 6 -- 20 times as high. As distance from the active source increased the ratio of measured concentration to the well-mixed prediction decreased. For most cases, ratios approached 1 (well-mixed) at distances of 3 -- 5 m from the source. Air change rate and vertical distance from source to receptor were two factors that affected horizontal concentration profiles. Under natural ventilation conditions, as air change rate increased, the concentrations close to the source became more elevated, magnifying the proximity effect. Mechanical ventilation increased mixing in the room, and resulted in a diminished proximity effect. Vertical mixing of the pollutant was even more hindered, due to temperature stratifications present in the rooms -- the concentrations more than 0.5 m vertically from the height of a nonbuoyant plume rapidly approached the well-mixed prediction. For buoyant stationary plumes, such as emissions from a smoldering cigarette or stick of incense, the height of maximum concentrations was typically 0.5 -- 1 m above the source, due to plume rise. The rise of a buoyant plume was more limited under natural than mechanical ventilation conditions, presumably due to less temperature stratification. For an actual smoker, where both highly buoyant sidestream smoke and less buoyant exhaled mainstream smoke were generated, and where the cigarette was moved around by the smoker, emissions were dispersed over a broader vertical extent. However, for 20 indoor experiments involving 2-4 people sitting in close proximity to an active smoker, the magnitude of the proximity effect within 0.5 -- 1 m was comparable to measurements for the stationary nonbuoyant source experiments.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Copyright date | 2011 |
| Publication date | 2011; 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Acevedo-Bolton, Viviana |
|---|---|
| Associated with | Stanford University, Civil & Environmental Engineering Department |
| Primary advisor | Hildemann, Lynn M. (Lynn Mary) |
| Thesis advisor | Hildemann, Lynn M. (Lynn Mary) |
| Thesis advisor | Boehm, Alexandria |
| Thesis advisor | Leckie, Jim, 1939- |
| Advisor | Boehm, Alexandria |
| Advisor | Leckie, Jim, 1939- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Viviana Acevedo-Bolton. |
|---|---|
| Note | Submitted to the Department of Civil and Environmental Engineering. |
| Thesis | Ph.D. Stanford University 2011 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Viviana Acevedo-Bolton
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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