ASHRAE Journal - February 2014 - S12

A filter test duct (photo courtesy LMS Technologies, USA)

Zen of Filter Classes
By R. Vijayakumar, PhD
Aerﬁl
Liverpool, New York

and

Marco Adolph, PhD
Trox Brasil
Curitiba - PR - Brazil

Abstract

About the Authors

Air ﬁlters of today are speciﬁed to meet several classes speciﬁed
by various national standards. Although many of these filter
classes appear to offer similar ﬁlter performance, none of them
are equivalent. Even the attempts at an international standard are
not expected to resolve this situation. In this article we argue that
drastically reducing the number of ﬁlter classes will not only reduce
the confusion in the market, but will not adversely affect outcome
on the occupants or the processes that are served by the ﬁltration
systems. Given that the variability in the test methods is large enough
for adjacent ﬁlter classes in many standards not to be statistically
different, there is strong justiﬁcation for taking this approach.

R. Vijayakumar is the founder and head of Aerﬁl, a consulting company
that provides technical and business solutions and training support for the
ﬁltration and contamination control industry. His clients include major ﬁltration
companies in China, Brazil and India. A Ph.D. in particle technology, he has
over 30 years' experience in leading ﬁltration and particle test instrument
companies, is an advisor to NASA for air ﬁltration systems for space habitat,
has been on the faculty of the short course on air and gas ﬁltration at the
University of Minnesota and is a Distinguished Visiting Professor at the
Chinese Academy of Building Research. He has taught courses in ﬁltration
and cleanroom designs as an ASHRAE DL, and has served as the President of
the IEST, the premier contamination control organization in the US. Currently,
he chairs standards development committees at the ISO and in the US for
high efﬁciency ﬁlters.
Marco Adolph is a bachelor in mechanical engineering from Federal
University at Parana (UFPR - Brazil). He completed his masters in mechanical
engineering in 2002, and a Ph.D. in mechanical engineering in 2006, both
from State University at Campinas (SP - Brazil). He completed his MBA
in project management at Fundação Getulio Vargas in 2012. He has been
working for TROX since 2006, with experience in R&D in Germany and
product management in Brazil. He was head of the Brazilian delegation at
ISO TC142 from 2008 to 2012. He also works at the Brazilian standardization
groups for ﬁlters and ﬁltration equipment, and is a part of Brazilian Society
for Contamination Control (SBCC).

Introduction
At the outset, we wish to unequivocally state that we are not
practioners of Zen, nor are we trained in the practice of this ancient
tradition. We use the term Zen in our title simply to convey that we
are acknowledging the focus on the simple, which is just a small
aspect of the practice of Zen. No disrespect to this ancient tradition
is intended or implied. With humility, we wish to learn from any
Zen masters who read this paper.
S12

February 2014
ASHRAE Journal - February 2014

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