Post-biogas perceptions of household biogas system.

<p>Post-biogas perceptions of household biogas system.</p

Map of study region showing participating villages near the city of Xichang in Sichuan Province, PRC.

<p>Map of study region showing participating villages near the city of Xichang in Sichuan Province, PRC.</p

Post-biogas survey participants and biogas usage.

*<p>Villages where biogas subsidies were made available.</p

Pre-biogas survey of energy usage by type.

<p>Pre-biogas survey of energy usage by type.</p

Laboratory Evaluation of the Shinyei PPD42NS Low-Cost Particulate Matter Sensor

<div><p>Objective</p><p>Finely resolved PM2.5 exposure measurements at the level of individual participants or over a targeted geographic area can be challenging due to the cost, size and weight of the monitoring equipment. We propose re-purposing the low-cost, portable and lightweight Shinyei PPD42NS particle counter as a particle counting device. Previous field deployment of this sensor suggests that it captures trends in ambient PM2.5 concentrations, but important characteristics of the sensor response have yet to be determined. Laboratory testing was undertaken in order to characterize performance.</p><p>Methods</p><p>The Shinyei sensors, in-line with a TSI Aerosol Particle Sizer (APS) model 3321, tracked particle decay within an aerosol exposure chamber. Test atmospheres were composed of monodisperse polystyrene spheres with diameters of 0.75, 1, 2 3 and 6 um as well as a polydisperse atmosphere of ASHRAE test dust #1.</p><p>Results</p><p>Two-minute block averages of the sensor response provide a measurement with low random error, within sensor, for particles in the 0.75–6μm range with a limit of detection of 1 μg/m3. The response slope of the sensors is idiomatic, and each sensor requires a unique response curve. A linear model captures the sensor response for concentrations below 50 μg/m3 and for concentrations above 50 μg/m³ a non-linear function captures the response and saturates at 800 μg/m³. The Limit of Detection (LOD) is 1 μg/m³. The response time is on the order of minutes, making it appropriate for tracking short-term changes in concentration.</p><p>Conclusions</p><p>When paired with prior evaluation, these sensors are appropriate for use as ambient particle counters for low and medium concentrations of respirable particles (< 100 ug/m³). Multiple sensors deployed over a spatial grid would provide valuable spatio-temporal variability in PM2.5 and could be used to validate exposure models. When paired with GPS tracking, these devices have the potential to provide time and space resolved exposure measurements for a large number of participants, thus increasing the power of a study.</p></div

Schematic of Experimental Set-Up.

<p>The blue circles indicate the location of the mixing fans inside the chamber.</p

Relationship between sensor response and particle diameter.

<p>Relationship between sensor response and particle diameter.</p

Response to low concentrations of Polystyrene.

<p>Response to low concentrations of Polystyrene.</p

Maximum detection limit (determined by modeling sensor response).

<p>Maximum detection limit (determined by modeling sensor response).</p

Shinyei PPD42NS.

<p>On the left is an exterior image of the sensor. On the right a view of the inside showing the positioning of the various sensor components. (A) Exterior view of sensor. (B) Interior view of sensor. This image was initially published on <a href="http://www.takingspace.org/make-your-own-aircasting-particle-monitor" target="_blank">http://www.takingspace.org/make-your-own-aircasting-particle-monitor</a></p