Inc. C leanrooms are designed to insure the area meets the necessary requirements of the clean production process. But what happens when the product changes and a
different manufacturing process must be put in
place along with new cleanroom requirements?
A similar dilemma can occur if production
needs require that the clean manufacturing
space double or triple because of product
demand. Such needs can be addressed by modu-
lar cleanroom constructions that allow revision
or expansion to meet the evolving prerequisites.
Unfortunately, many cleanrooms cannot be
easily expanded or reconfigured, and they still
adhere to the mandatory ISO classifications.
Many modular cleanrooms are not supplied
with door interlocks and must be retrofitted in
the field. As a result, cleanroom manufacturers
benefit from utilizing door interlock controls as
an option for new and existing installations as a
means of addressing these changing conditions.
The addition of door interlocks not only
assures the cleanroom meets the necessary ISO
classifications by enforcing clean air control,
but can also add a level of security within the
controlled environment of the cleanrooms.
Depending upon the manufacturing process,
interlock system considerations may include:
Air system control
• Traffic controls
• User feedback indication
• Automatic door openers
• Emergency override
• Access control
• Door alarms
The construction of some modular clean-
rooms may limit the number and types of
interlock devices that may be compatible. This
is frequently addressed with factory custom-
ized mounting hardware for locks and control
switches. Fixed construction cleanrooms may
utilize standard locking devices.
Choosing the right door interlock system can
involve both construction limitations and building code requirements. Some locations may
not allow any doors to be locked to permit free
egress at any time. While this unlocked scenario
provides for personnel safety, door violations
may become a common occurrence. This has
been addressed with the use of red/green traffic
lights mounted on either side of the doors to
indicate when access is allowed. Adding a built-in sounder which annunciates an improper
opening can minimize such actions.
Some cleanrooms require a pressurized air
system to maintain the sterile environment.
This may force doors to utilize a timed delay
before the second door can be opened. This
re-pressurization of the interlock could be a
simple timer or may incorporate a monitored
pressure switch. While the air is pressurized,
traffic indicator lights might be employed to
provide user feedback.
While automatic door openers are frequently
used to provide touch-free access or to allow
easy movement or materials, special considerations are required if interlocking door controls
are involved. Most overhead doors have operators that use open, close and stop push button
controls. These doors cannot be opened manually, so if the door should remain closed while
Managing Changing Cleanroom Operations
Locks, alarms, and pressurized air systems help prevent
contamination in controlled environments.
Choosing the right door
interlock system can
and building code