10 FACILITY MONITORING
Acleanroom is a controlled environment spe- cially designed to keep the concentration of contaminants to a minimum. So we are all on the same page, contamination can be defined
as a process or an action that causes surfaces, instruments, or equipment to become soiled with contaminating substances.
These substances can include pathogens
(germs, bacteria, toxins), threads and fibers, fluids, and soils, among other things. When on a
surface, they can cause what is termed a “killer
defect,” which can skew testing procedures and
results conducted in the cleanroom.
One of the key ways cleanrooms are kept
contamination-free is by proper air flow and filtering the air released in the room. For instance,
while the air in a typical office building may have
500,000 to 1,000,000 particles — 0.5 microns or
larger — per cubic foot of air, a Class 100 clean-
room will be designed to never allow more than
100 particles, 0.5 microns or larger, per cubic foot
of air to be released in a cleanroom.
However, there is a lot more involved in keeping
a cleanroom environment contamination free than
just air flow and the number of microns in the air.
Even when safeguards are taken, contamination in
a cleanroom can still be generated by people, pro-
cesses, equipment, the garments worn in a clean-
room, materials brought into the cleanroom, etc.
Further, very often the very tools and equip-
ment used to keep the cleanroom clean are the
culprits. This is especially true when floors
are damp mopped. As the mopping procedure
advances, the cleaning solution begins to lose
its efficacy. This means the cleaning solution
becomes less effective as the floor is mopped.
Avoiding the “Killer Defect”