high number of air nozzles positioned as close to the
worker or product as possible. Ideally these nozzles
should be positionable as well as removable to allow
for easy inspection of the high-pressure supply ducts.
An air shower’s recirculating air filtration systems
typically use two sets of filters. The first is a pre-filter
for catching the bulk of contaminants. The second is
a high-capacity, 99.97 percent-efficient HEPA filter.
System blower units are usually mounted in the
ceiling. If your facility has height restrictions, make
sure the blowers can be mounted on the external
wall. For easy routine maintenance, pre-filters should
be changed regularly. Replacement filters are economical and easy to change.
Modular air shower designs and configurations
accommodate specific requirements for industry
as well as the number of personnel using the cleanroom. Modular cleanroom entry systems also simplify shipping and assembly.
A straight-through air shower with nozzles on
two opposing walls cleans workers with
ease. In a 90-degree design, users enter
on one side and exit to the right or left
at a 90-degree angle. This configuration
has fewer air nozzles than the straight-through design and requires the worker
to turn 360 degrees to ensure sufficient
cleaning. Other designs may have double doors or even three doors for entry
and exit. Configurations include cart/
parts-cleaning air showers, used for
carts, conveyors, pallets and contin-uous-part operation. Low-profile air
showers accommodate facilities with
ceilings less than 96 inches. ADA air
showers are sized so a wheelchair can
turn around in the air shower. The
space between nozzles on opposite air
shower walls is usually about 36 inches.
Standing between nozzles, an aver-age-sized worker will be about eight
inches away from any one nozzle. At that
distance air velocity is in the 6,500 to
7,000 fpm range which is still an effective cleaning force.
The number of people that need to
enter your cleanroom in a given amount
of time will have a major impact on the
size of the air shower. Designs range
from single batch systems where one
person uses the shower at a time to
tunnel systems for larger groups to pass
HEPA filters sealed
with an upstream and
ensure zero-leak reliability
and simplify filter
through quickly. Tunnels are becoming more common because of the amount of cycle time needed for
a shift change.
Kevin Weist is President of Clean Air Products.