in the HACCP and zoning risk assessments. These cleaning tasks should have
documented and detailed procedures,
a defined frequency, and adequately
trained associates performing the tasks.
Surfaces within the AHUs and associated ductwork should be smooth
and nonabsorbent. Exposed fiber insulation, foam insulation, and other such
noncleanable surface materials must be
avoided for adequate
cleaning to occur. Ideally, noncontinuous
welds and lap joints
should be minimized
to avoid harborages
for foreign material
and microorganisms. The amount of
ductwork should be
minimized. This will
reduce cost of installation and maintenance.
Accessibility for Cleaning
The AHU can be
located on the roof,
in an interstitial space
between the production room and the
roof, or in an area adjacent to the room.
Roof locations are least desirable due to
contaminants present as well as snow,
ice, and rain. The ease and convenience
of accessibility for cleaning and inspection have a direct relationship to efficiency and effectiveness of the process.
Employee safety is of utmost importance and must be considered.
The ductwork may be metal or
fabric. Without access doors appropriately spaced along the length of the
ductwork, the interior surfaces of metal
ducts are difficult to clean and inspect.
If access doors do not exist, they will
need to be installed. These installations create metal shavings and sharp
edges that need to be corrected. Finally,
cleaning and inspection of these ducts
require extremely important safety considerations related to working at heights.
Ductwork is either supplying air to
a space from an AHU or returning air
from the space to the AHU. The air
passing through the supply ducts has
been filtered, so these ducts typically
remain cleaner than the return ducts.
Return ducts will collect airborne con-
taminants from the room over time.
The more dust, fumes, smoke, etc. gen-
erated in a room, the more accumula-
tion will occur inside the return ducts.
Fabric ducts offer several advantages
over metal ductwork. Foremost, they
can be easily taken
down and laundered.
However, in wet-
they have a tendency
to show spots when
droplets mix with dust
that may be present in
or on the duct. Fabric
ducts minimize or
eliminate drafts that
are normally associ-
ated with individual
vents in metal ducts.
Fabric ducts may have
into their design or
have no vents at all,
and the entire duct diffuses the air
through the fabric.
In rooms with low ceilings, fabric
ducts may not be appropriate, as they
must be suspended from a ceiling and
possibly cause overhead clearance issues. Metal ducts can be installed above
the ceiling, very close the ceiling, or
have a single vent blowing air a long
Finally, metal ducts should not be
painted when installed in environments
that are wet-cleaned. In these conditions, peeling paint and corrosion are
likely to occur.
Absence of Hollow Bodies
Ideally, framework inside and outside
the AHUs and associated ductwork
should not contain hollow bodies.
These are typically square or round
frameworks that support the AHU or
components such as the blower, filters,
maintenance enclosures, etc. Suit-
able alternatives include solid square
or round stock. Another alternative is
angled stock mounted diagonally with
the 90-degree angle pointed upward.
Threaded rods, also called “all-thread,”
should always be avoided as they are
not easily cleanable.
Absence of Areas Where Accumulations
Of particular concern is the condensation drain system underneath cooling
coils. Mold growth and insect activity
are not unusual in drip pans and drainage lines. When properly sloped, these
condensation drain systems will be less
likely to cause hygiene problems. Accessibility to clean the pans is important,
as is proper condensate piping so pans
drain without holding water.
Other areas of accumulation include
the top surfaces of the AHU and metal
ductwork. These horizontal surfaces can
be properly sloped so accumulations are
minimized. In some instances, the areas
underneath the AHU and the associated
ductwork are prone to accumulations
of condensation and other materials.
Clearance, accessibility, and proper
slope will make cleaning and inspection
Compatibility of Construction Materials
with Food Product and Cleaning
Engineering, quality, the AHU and
ductwork manufacturer, and the factory’s cleaning chemical supplier can arrive at the correct construction materials
during the design phase of the system.
This evaluation will need to consider
the food product type as well as the
cleaning chemistry, methods, frequency,
and any safety considerations. These
resources must be involved in creating
the cleaning procedures to ensure effective, efficient methods achieve optimal
results and damage does not occur to
the AHU system.
One important consideration for
hygienic AHUs and ductwork includes
the physical location of AHUs. Systems
that supply air to production areas
“Air handling in
factories is quite
different from air
handling in commercial