Even the ambient air has to be monitored
and maintained at proper levels. HEPA-filtered
ventilation systems, assisted by preventive
measures, help manufacturers limit
airborne contamination. However, in order
to assure environmental purity, regular
housecleaning procedures are also necessary.
Cleaning with both a HEPA-filtered vacuum
and traditional wipe-down methods are
standard housekeeping procedures in most cleanrooms. Yet in critical cleaning situations,
vacuuming may be the more efficient
method because particles are retained inside
the machine with little chance of being exhausted
into the atmosphere (provided the vacuum has a HEPA-filtered exhaust
stream).
So, what should a cleanroom vacuum include?
According to the people at Nilfisk
CFM, which manufactures vacuums for Class
1 and Class 10 cleanrooms, any vacuum
cleaner used in a biotech, parenteral cleanroom
must be HEPA-filtered to ensure that
99.97 percent of all particles down to and including
0.3 microns are collected and retained.
In addition, it is absolutely critical that the
HEPA filter be installed after the motor to
filter the exhaust stream. The motor’s commutator
and carbon brushes generate dust,
and if the exhaust stream is not filtered that
dust will be released into the environment.
A word of caution: not all HEPA-filtration
systems are created equal. Nilfisk recommends
that the vacuum contain a
multi-stage, graduated filtration system for
peak operating efficiency. A graduated filtration
system uses a series of progressively finer filters to trap and retain particles as they
move through the vacuum.
The largest particles are captured first by
coarser filters; smaller particles are then
caught and retained by the finer HEPA filters.
This multi-stage system protects the
HEPA filters from blockage and excessive
wear-and-tear, maintaining peak performance.
(When equipped with an ultra low
penetration air (ULPA) filter, the system
should retain up to 99.999 percent of all ultra-
fine particles, down to and including 0.12
microns in size).
Additionally, the filtration system in your
vacuum should use oversized filters, which
