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8 Indoor Particulate Matter Exposure Control and Mitigation
Pages 81-98

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From page 81...
... Following the three presentations, Rengie Chan and Seema Bhangar moderated an open discussion with the panelists. PM2.5 FILTRATION AND AIR CLEANING IN RESIDENTIAL ENVIRONMENTS Indoor air filtration, said Jeffrey Siegel, involves more than just a device or filter.
From page 82...
... . Another important parameter regarding air flow is runtime, the fraction of time that the HVAC system operates, and that varies, too, depending on the weather and other FIGURE 8-1  Home air volumes that pass through a filter when the heating, ventilation, and air conditioning system is operating in residences sampled in 3 studies in selected North American locations.
From page 83...
... In the laboratory, FIGURE 8-2  Fraction of time that a heating, ventilation, and air conditioning system operates. SOURCE: Siegel slide 4, adapted from Touchie and Siegel (2018)
From page 84...
... First, it is not relevant to many filters installed in residential buildings, but rather intended for filters used in commercial buildings; second, it is a laboratory standard, not an in situ standard; and third, it addresses only particles in the defined size ranges. In situ testing shows how various electret2 and nonelectret filters perform in homes as opposed to in a laboratory setting (Figure 8-4)
From page 85...
... . MERV = minimum efficiency reporting value.
From page 86...
... Noting that other speakers in the session would be talking more about portable air cleaners, Siegel did comment that the same issues apply to these cleaners. In addition, placement of a portable cleaner relative to particulate matter sources makes a big difference in effectiveness and performance (Novoselac and Siegel, 2009)
From page 87...
... Third on Siegel's list of research needs would be to understand what exposures filters have avoided in the environments in which they have been deployed. In some 60 to 70 articles, investigators have used what he called filter forensics to quantitatively link contaminants extracted from HVAC dust filters to time-averaged integrated air concentrations (Haaland and Siegel, 2017)
From page 88...
... Over the past several years, Gall and the members of his research group have been studying traffic-related air pollution constituents in a middle school in Portland, Oregon, that was renovated in 2018 to serve Portland's historically Black community. The school is adjacent to Interstate 5, and measurements of black carbon, ultrafine particles, and PM2.5 taken on the school's rooftop prior to the renovation showed elevated levels of these three types of particulate matter, with the exact burdens changing with wind speed and direction.
From page 89...
... Research suggests that, in general, the health effects associated with traffic-related air pollutants such as black carbon (Janssen et al., 2011) and ultrafine particles (Schraufnagel, 2020)
From page 90...
... In the case of the Portland middle school, the contractor installed a single air handler to serve the entire school. This air handler was outfitted with an advanced air cleaning system comprising a MERV-8 prefilter, a MERV-16 filter, and functionalized carbon that targeted gas-phase species that might be elevated in a near-roadway environment.
From page 91...
... In the Portland middle school, the carbon scrubber component of the air cleaning system appears to suppress levels of secondary organic aerosol precursors and thus formation of secondary organic aerosols. Monitoring showed that there is very little particle formation when the air handling system is on, but higher total particle counts in the indoor air than in outdoor air when the system is off.
From page 92...
... There are some standards and codes that require kitchen ventilation, of which ASHRAE 62.2 is the most prominent; others include those promulgated by the California Building Code, the Home Ventilating Institute, Energy Star, and the International Residential Code. The basic requirement of ASHRAE 62.2 is to have a range hood above the stove that moves air more than 100 cubic feet per minute (cfm)
From page 93...
... . The installed range hoods provided varied levels of exposure reduction, with the best performance seen with a hood that extended over the entire stove.
From page 94...
... The problem is that if the HVAC system is running only 10 percent of the time, then 90 percent of the time it does not matter what the MERV rating is. An audience member asked Gall if there is a level of airborne black carbon that is high enough that schools should not allow outdoor activities.
From page 95...
... But, he added, "it becomes quickly a very political process to say where students can go, when can they go there, what is outdoor recess going to look like at a near-roadway school." Asked how the Portland school fared during Oregon's bad wildfire season in 2020, Gall said that he did not have intensive monitoring then, but there were low-cost particle monitors in the school that indicated that the HVAC system did a good job of keeping PM2.5 levels low inside the school during the wildfire event. In fact, there were discussions with the school district and local county health department about the possibility of using the school as a clean air shelter for those who might seek to reduce their exposure during a wildfire.
From page 96...
... Turning to the subject of range hoods, Chan asked Singer to comment on the idea of phasing out gas stoves as a solution to the indoor particulate matter issue. Singer replied that getting rid of gas stoves would eliminate one important source of ultrafine particles and nitrogen oxides, though it does not remove the need for good ventilation.
From page 97...
... Singer added that a test method for low-cost particulate matter monitors is making its way through the ASTM5 process and his hope is that when it is produced it will allow a consistent standard to be applied to these monitors. While this standard will be imperfect -- as all standards are -- it will serve as a general reference and help consumers distinguish between products that work fairly well from those that do not work at all.


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