Electret, What Are The Important Parameters That Need To Be Considered Presented at 2005 NAFA Annual Convention September 23, 2005 by Ker-Ching (K.C.) Hsieh, Ph,D. Particle Tech, Inc. St Paul. MN

Filtration Mechanisms For Electret Mechanical Filtration Mechanisms Diffusion Interception Inertial Impaction Electrostatic Filtration Mechanisms Dielectricphoretic Effect/Force Columbic Force Image Force

Performance Of A Chargeable Media If It Is Not Charged

Performance Of A Chargeable Media After It Is Charged

Net Effect—Higher Average Life Time Efficiency

Examples

Particle Deposition On A Single Fiber

Possible Gradient Structure

Important Parameters Need To Be Considered For Electret Initial efficiency Initial efficiency without charge Shelf life performance Environmental conditions Special parameters aerosol contains alcohol, alcohol vapor and other chemicals, oily aerosol, combustion generated aerosol…..

Electrostatic Index

Examples EI1

Initial Efficiency With And Without Charges

Shelf Life Tests

Temperature Effect

Humidity Effect

Effect of High Temperature and High Humidity

Real Life Performance of Electret : 1

Real Life Performance of Electret: 1

Real Life Performance of Electret: 1

Real Life Performance of Electret: 2

Real Life Performance of Electret: 2

Cigarette Smoke Test

Cigarette Smoke Test

Summary Charged media are “quite different” from non-charged media. Charged media have a completely different set of parameters that need to be considered when they are used. Is it premature for ASHRAE 52.2 to try to use a simplified method to try to compare charged filters and non-charged filters?

Summary Is the “conditioning” step going to solve the disputes between the charged media manufacturers and non-charged media manufacturers? Answer: “No”, on the other hand, it will bring in a whole new set of problems. “MERV” is strange enough, please don’t make things more confusing by adding this conditioning step.