Understanding Climate Impact and Indoor Emission Nexus: Size Resolved Exfiltration Factor

Abstract

<p>One-third of the Indian population relies on biomass for cooking and heating which makes the residential sector a major source of particulate matter (PM)<sub> </sub>emissions. The climate impact of indoor PM depends on the fraction of particles advecting out of the house, which is either not considered in climate impacts or some thumb rule is used. The removal mechanism can have a distinct impact on different size ranges, thus size-based characterization of exfiltration factor (fraction of particles that are advected outdoors) is very important to underpin accurate climate impact. This study examines the size-dependent ExF of PM and the influence of different parameters such as room size, type of circulation, and ventilation status on exfiltration factor (ExF). CO is used as a reference gas to understand decay associated with the air exchange, while PM removal is considered to be dependent on deposition and air exchange. An Optical Particle Sizer and an Indoor Air Quality Monitor are used for PM and CO real-time measurements. We find a significant difference in PM<sub>2.5</sub> ExF during natural (25±7 %) and forced (34±12 %) circulation. PM<sub>2.5</sub> ExF was lowest  (i.e. 22%)  when both door and window were closed. Opening the window or both window and door increased the exfiltration slightly (26 and 27 %,  respectively). However, the exposure time to significantly elevated indoor PM levels can vary from 10 mins to 360 mins depending on ventilation, thus health impacts can differ significantly due to ventilation despite having an insignificant change in climate impacts. Size-based ExF for PM<sub>0.9</sub>, PM<sub>2.5</sub>, and PM<sub>10</sub> ExF were 43±28, 30±9 and 29±9 % respectively.The integration of ExF, total PM emissions, and kitchen-type information would bring more certainty to the climate impact assessment. An extended analysis is underway to understand the importance of room size and shape.</p> <p> </p> <p><img src="" alt="" /></p> <p>Figure 1. The decay of gas and aerosol concentration from the room under different removal mechanisms. (Here, EF stands for emission factor)</p>