Measured performance of filtration and ventilation systems for fine and ultrafine particles and ozone in an unoccupied modern California house

Abstract

This study evaluated nine ventilation and filtration systems in an unoccupied 2006 house located 250m downwind of the I-80 freeway in Sacramento, California. Systems were evaluated for reducing indoor concentrations of outdoor particles in summer and fall/winter, ozone in summer, and particles from stir-fry cooking. Air exchange rate was measured continuously. Energy use was estimated for year-round operation in California. Exhaust ventilation without enhanced filtration produced indoor PM 2.5 that was 70% lower than outdoors. Supply ventilation with MERV13 filtration provided slightly less protection whereas supply MERV16 filtration reduced PM 2.5 by 97-98% relative to outdoors. Supply filtration systems used little energy but provided no benefits for indoor-generated particles. Systems with MERV13-16 filters in the recirculating heating and cooling unit (FAU) operating continuously or 20 min/h reduced PM 2.5 by 93-98%. Across all systems, removal percentages were higher for ultrafine particles and lower for black carbon, relative to PM 2.5 . Indoor ozone was 3-4% of outdoors for all systems except an electronic air cleaner that produced ozone. Filtration via the FAU or portable filtration units lowered PM 2.5 by 25-75% when operated over the hour following cooking. The energy for year-round operation of FAU filtration with an efficient blower motor was estimated at 600 kWh/year. KEYWORDSResidential filtration, PM 2.5 , Ultrafine particles, Black carbon, Residential ventilation PRACTICAL IMPLICATIONSThis study quantitatively demonstrates the potential for advanced filtration to reduce in-home exposures to outdoor air pollutants through engineered systems. It also demonstrates that high quality filtration is required on supply ventilation systems to achieve the same reductions of outdoor particles as exhaust ventilation in a moderately airtight home. Results from this work should help inform the setting of filtration requirements for high performance home standards and building codes.

Time-Resolved Measurements of Nitric Oxide, Nitrogen Dioxide, and Nitrous Acid in an Occupied New York Home

“…In addition to extending the lifetimes of unsaturated VOCs, this would reduce production of OH via ozone–alkene reactions, which is thought to be the dominant OH source indoors (except potentially in sunlit regions). Previously reported indoor ozone levels ranged from 1.6 to 50 ppbv, although most of these measurements were not made in residences (e.g., refs , , and ). A median indoor ozone level of 25 ppbv results in a dark OH production rate of ∼10 7 molecules cm –3 s –1 .…”

Using Building Energy and Smart Thermostat Data to Evaluate Indoor Ultrafine Particle Source and Loss Processes in a Net-Zero Energy House

“…Table lists the number of occurrences for each mode from which UFP loss rates were estimated during the concentration decays. L represents the total rate of removal of UFPs and incorporates the additive effects of (i) deposition to indoor surfaces, − (ii) deposition to AHU components (e.g., MERV 11 filter, heating/cooling coils, ducts), ,, (iii) exhaust to the outdoors via the ERV, (iv) exfiltration through the building envelope, − and (v) interzonal air exchange . Thus, the apportionment of L among processes (i)–(v) was not determined.…”

Creating Clean Air Spaces During Wildland Fire Smoke Episodes: Web Summit Summary

“…The efficiency and the size range of PM removal varies with the MERV ratings with the smallest particles and highest removals achieved with HEPA filters and MERV 13 and greater. Unsurprisingly, studies have shown higher MERV filters are more effective at cleaning indoor air than lower MERV filters ( 28 ). The presenters recommended MERV 13 or greater filters for wildland fire smoke filtration, since these filters have some effectiveness removing the smallest particles (0.3–1.0 μm) that are most common in wildfire smoke.…”