Page 55 - MASHRAE 35th Anniversary

Comparison and Discussion
The differences between ASHRAE 52.2 and ISO 16890 is shown in table 1,
Table 1: Comparison of ASHRAE 52.2:2017 and ISO16890:2016
ASHRAE 52.2 and ISO16890 both are designed for primary and secondary filter efficiency classification. Both of these standards are focused on 0.3-10􏰀m particle. The point of debate is that ISO 16890 uses 2 types of testing aerosol which are DESH and KCI, while ASHRAE 52.2 only uses KCI. In ISO16890, DESH is used to generate 0.3 to 1.0um dust particle while KCI is used for 1.0 to 10􏰀m. The different test aerosols used in ASHRAE 52.2 and ISO16890 means that the test results cannot be compared to on an apple to apple basis. Moreover ISO16890 allows the use of other aerosols that matches their required criteria. The toleration of the aerosol in ISO16890 will affect the accuracy of the test result that may bring confusion to the industry. KCI is a water soluble base chemical, DESH is an oil base chemical. Oil base chemical will easily to stick on the duct and cause difficulties in the test duct maintenance. (Hartley,2011).
Both of the standards use optical particles counters to capture the concentration of the aerosol. Optical particle counters using white light illumination source and a wide collection angle for the scattered light. ASHRAE 52.2:2017 required the optical particle counters sampling rate at 0.00012m3/s (ASHRAE,2017).
The test rig required in ASHRAE 52.2:2017 is to be constructed with a 180􏰁 deg􏰃ee bend downstream (ASHRAE,2017). The purpose of the bend is to bring the downstream and upstream sampling location closer, allowing short sample lines to the particle counter. ISO16890 allow both bend duct and straight duct. The test duct materials for both of the standards need to be electrically conductive and electrically grounded with smooth interior finish and rigid enough to withstand 3200pa with less that 1% airflow leakage on highest pressure anticipated. The test duct required in ASHRAE 52.2:2017 must be positive pressure, ISO 16890:2016 accepted both positive and negative pressure test duct.
ASHRAE 52.2:2017 allows the test room temperature to be in range of 10􏰁C 􏰄􏰅 38􏰁C, 􏰄hi􏰆 􏰇ill affec􏰄 􏰄he fil􏰄e􏰃 efficiency especially against the small particles 0.3um. In higher temperature the filter diffusion mechanism will reduce due to Brownian motion. When the temperature rise, the Brownian motion of the particle is relativity higher, the small particle will more easily escape and penetrate the filter. ISO 16890:2016 requires the test room to be set at 23􏰈5􏰁C, and 􏰃ela􏰄i􏰉e h􏰊midi􏰄􏰋 a􏰄 45􏰈10%.
Table 2 and table 3 shows the air filter efficiency classification of ASHRAE 52.2:2017 and ISO16890:2016 respectively. ASHRAE 52.2:2017 rated the efficiency of the air filter with Minimum Efficiency Reporting Value (MERV), MERV 1 to MERV 16, total 16 grades. ISO 16890:2016 separates the air filter grade into 4 categories which is ePM1, ePM2.5, ePM10 and ISO Coarse. Filter efficiency is shown in percentage that is defined together
Test Aerosol
Particle Size Range Sampling Instrument
Test Duct
Test Rig Pressure
Test room Temperature Relative Humidity
ASHRAE 52.2
Solid phase Potassium Chloride- KCI
0.3 to 10􏰀m Optical particle
counters Bend duct
Positive
10􏰁C to 38􏰁C Less than 50%
ISO 16890
DiEthylHexylSebacate -DESH
& KCI
0.3 to 10􏰀m
Optical particle counters
Bend duct or straight Duct
Positive or negative
23 ±5􏰁C 45 ±10%
Duct Leakage
Less than 1% of total air flow with highest pressure anticipated
Less than 1% of total air flow with highest pressure anticipated
Down Stream Exhaust Air
Downstream duct with HEPA filter, the exhaust can be recirculate
Downstream duct with HEPA filter, the exhaust can be recirculate
Airflow Range
Test at an airflow rate corresponding to 2.50 m/s
if an air velocity has not been specified.
The test deceive shall be tested at its nominal air volume flow rate for which the device has been specified by the manufacturer. Otherwise test with the volumetric flow rate 2.54m/s
Arrestance Filter
Filter efficiency less than 20% in Range 3 (3.0 to 10􏰂m)
Filter efficiency less than 50% in ePM10
Passive Electrostatic Charge Final pressure requirement
Allow 350 Pa
Discharge required
ePM
ePM10≥ 50%: 300Pa
<50%: 200Pa 10
Loading dust
ISO 12103-1 A2 , 72% , 23% carbon, 5% milled cotton linters
ISO 15957 L2 dust, volume 3
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