Evaluating the Sensitivity of the Mass-Based Particle Removal Calculations for HVAC Filters in ISO 16890 to Assumptions for Aerosol Distributions

Abstract

High efficiency particle air filters are increasingly being recommended for use in heating, ventilating, and air-conditioning (HVAC) systems to improve indoor air quality (IAQ). ISO Standard 16890-2016 provides a methodology for approximating mass-based particle removal efficiencies for PM 1 , PM 2.5 , and PM 10 using size-resolved removal efficiency measurements for 0.3 µm to 10 µm particles. Two historical volume distribution functions for ambient aerosol distributions are assumed to represent ambient air in urban and rural areas globally. The goals of this work are to: (i) review the ambient aerosol distributions used in ISO 16890, (ii) evaluate the sensitivity of the mass-based removal efficiency calculation procedures described in ISO 16890 to various assumptions that are related to indoor and outdoor aerosol distributions, and (iii) recommend several modifications to the standard that can yield more realistic estimates of mass-based removal efficiencies for HVAC filters, and thus provide a more realistic representation of a greater number of building scenarios. The results demonstrate that knowing the PM mass removal efficiency estimated using ISO 16890 is not sufficient to predict the PM mass removal efficiency in all of the environments in which the filter might be used. The main reason for this insufficiency is that the assumptions for aerosol number and volume distributions can substantially impact the results, albeit with some exceptions.

Fine and ultrafine particle removal efficiency of new residential HVAC filters

“…A literature review was conducted to identify previous studies that reported measurements of indoor PSDs in a variety of (mostly residential) indoor environments, including those with indoor sources present, such as cooking, burning incense, and others. The purpose of the review was to gather a wide enough variety of PSDs to explore how variations in indoor PSDs might influence estimates of integral measures of PM 2.5 and UFP removal efficiency . Google Scholar was used to search for the following terms: indoor concentration, particle size distribution, particle size characterization, SMPS, ultrafine particle emissions, and fine particle emissions.…”

“…The purpose of the review was to gather a wide enough variety of PSDs to explore how variations in indoor PSDs might influence estimates of integral measures of PM 2.5 and UFP removal efficiency. 26,43 Google Scholar was used to search for the following terms: indoor concentration, particle size distribution, particle size characterization, SMPS, ultrafine particle emissions, and fine particle emissions. Sixteen studies reporting a total of 201 PSDs were selected for analysis through this procedure.…”

“…The International Standards Organization (ISO) recently published a new series of filter test standards (ISO 16890) that use size‐resolved removal efficiency data from laboratory testing (although only for 0.3 to 10‐µm particles) to approximate mass‐based particle removal efficiencies for PM 1 , PM 2.5 , and PM 10 . However, ISO 16890 is still not widely adopted in the US market, and the aerosol distributions used in the standard to estimate mass‐based removal efficiencies come from historical ambient data, which do not necessarily reflect modern indoor environments . Last, data from laboratory tests may not yield results that are directly relevant to in situ field performance, which could differ substantially based on filter face velocity, aerosol source, and other factors that influence particle removal efficiency …”

“…42 However, ISO 16890 is still not widely adopted in the US market, and the aerosol distributions used in the standard to estimate mass-based removal efficiencies come from historical ambient data, which do not necessarily reflect modern indoor environments. 43 Last, data from laboratory tests may not yield results that are directly relevant to in situ field performance, which could differ substantially based on filter face velocity, aerosol source, and other factors that influence particle removal efficiency. 44 To address some of these limitations, the objectives of this study are to: (a) measure the size-resolved particle removal efficiency for particle sizes ranging from 10 nm to 2.5 µm of a sample of 50 new commercially available residential HVAC filters from 10 different manufacturers; and (b) combine the measured efficiency data with a large number of indoor particle size distribution (PSDs), collected from a literature review, to estimate integral measures of total UFP and PM 2.5 removal efficiency for these filters in a range of indoor residential environments.…”

A review of air filter test standards for particulate matter of general ventilation

“…ASHRAE 52.2 uses the resulting size-resolved removal efficiency data to classify the average filter efficiency in three aggregate particle bins. 17 The efficiency is analysed at size ranges, from 0.3 to 1.0 mm, 1.0 to 3.0 mm and 3.0 to 10.0 mm. The minimum efficiency at different sizes within the three respective small ranges are averaged and classified according to MERV.…”