Application Note

When such problems occur, an airborne particle counter
such as the Fluke 983 can help hospital staff and industrial
hygienists detect increased particle levels, identify the
sources and verify the effectiveness of remedial action.
The Fluke 983 Particle Counter
operates by pumping an air sam-
ple of known volume—generally
one liter—past a laser beam. As
dust particles in the air stream
pass through the beam, each one
reflects or “scatters
” the laser
light
. A photodetector senses the
scattered light and generates an
analog electrical signal. Larger
particles scatter more light and
create higher-voltage electronic
“hits.” Onboard electronics track
the hits and count the particles in
six size categories, ranging from
.3 microns to 10 microns.
Particles larger than 10 microns
generally settle out of the air.
The Fluke 983 can be pro-
grammed to take repeat counts
instantly, or delayed up to 24
hours between samples. It can
store 5000 records of date, time,
counts, relative humidity, temper-
ature, sample volumes, alarms
and location label records in its
onboard memory. Stored readings
ma
y then b
e dow
nloaded to a
personal c
omputer
. As an alter
na-
tive, the particle counter can be
c
onnected directly to a P
C for real
time dow
nloads
.
According to the CDC,
“P
articulate sampling (i
.e., total
numb
ers and size range of partic
-
ulates) is a practical method for
evaluating the infection-c
ontrol
performanc
e of the H
VAC system,
with an emphasis on filter effi-
c
ienc
y in remov
ing respirable
particles (< 5
µm in diameter) or
larger particles from the air.”
v
The ac
curac
y, speed and
c
ompact size of the Fluke 983
make it useful for baseline partic-
ulate testing, problem detection
and remediation and system
maintenance.
•
Baseline Testing. To know
when the “abnormal” occurs,
it’s necessary to document
what are normal levels of par-
ticles. According to Andrew
Streifel, it’s not reasonable to
expect “clean room” conditions
in a healthcare setting. When
staff rush into a room to inter-
vene in a patient emergency,
there’s no time to worry about
air quality. Particle counts will
soar with the presence of mul-
tiple people (human beings
shed some 500,000 particles
each minute) and medical pro-
cedures too can contaminate
the air. But later, counts should
return to normal or baseline
levels. Best practice calls for
baseline particulate levels to
be documented, both within
spaces and in the supply air
flowing into the space.
•
Maintenance Testing. Once
baseline or “normal” particle
levels are determined,
followup tests should be
performed and documented
periodically. These followup
tests can provide early warn-
ing of developing anomalies
and enable the facility
manager to intervene before
anyone gets sick.
•
Filter Testing. Used to test for
particle levels in the air
upstream and downstream
from filter media, the Fluke
983 can verify that filters are
performing as they should.
Testing the level of particles
in incoming filtered air at the
diffuser (air grate)—air that
should be the cleanest in the
room—provides an additional
check on the performance of
filtration systems.
Contamination Testing with Airborne Particle Counters
4 Fluke Corporation Airborne particle counters provide vital information for maintaining indoor air quality in healthcare facilities
Writing in HPAC Engineering
magazine, Streifel said “when
dealing with filtration testing,
the verification data should
be reflected with objective
analysis by providing
airborne-particle comparison
with the specifications of filter
efficiency for fan systems. The
objective analysis available
toda
y should provide function-
ing pressure gauges,
inspection information of the
filter bank
s, and objective
particle analysis of filters for
filtration leaks. The particle-
analysis procedures at this
time are not standardized but
yet the comparison of before
versus after filter tests with
atmospheric dust particle
sizing will help to assure that
the 90-percent-efficient filter
is removing 90 percent of the
particles greater than 0.5 µm.”
vi
•
Locating Particle Sources.
The Fluke 983 can help
identify areas where particle
counts are elevated and,
ultimately, lead the user to
the source. A leaking air duct
could be sending unfiltered
air into a room, for instance;
work ab
ove a suspended
ceiling could be disturbing
accumulated dust.
•
V
erify
ing the Eff
ectiveness
of R
emediation
.
Onc
e the
causes of higher particle
c
ounts ha
ve b
een addressed,
post-testing w
ill show
whether the fixes employed
ha
ve really worked at bring
ing
particulate levels dow
n
.
Controlling airborne contamina-
tion within healthcare facilities
poses a complex set of challenges
far beyond the scope of this
paper. Numerous additional
resources are available to help
the professional understand and
overcome those challenges.
Among those easiest to grasp is
the Fluke 983 handheld airborne
particle counter.