interlockedand caulked.Insulation shouldneverbe placedinsidean air duct. If
insulationis required, a sandwich ductconstruction shouldbe used.The outside
surface is hard,the innersurface is hardand the insulationis enclosedbetween
the twosurfaces. If insulation is left exposed it willbecome dampand a
substrate for microbial growth. The microbes are thenspreadthroughout the air
distributionsystem. The ducts all requireclean-out ports.Ideallythey are placed
about5 feet (1.5 m) apart.Some air systemsin plantswithhighlymicrobial
sensitive products are installing CIP systems insidethe ducts.The ideal HVAC
system:
∑ cools and heats;
∑ humidifies and/or dehumidifies;
∑ filtersfor clean air;
∑ keepsductworkout of the room;
∑ is not a contaminationsource;
∑ pressurizesthe room.
In rooms,evaporatorsare not alwaysthe mostsanitarychoice. The drip pans
can becomea source of contamination. The drip pansshouldbe sloped to a drain
so the condensate can continually drainto a floordrain.It is recommendedthat a
sanitizerblock be placedat the low pointof the drippan.It should alsobe
routinelycleanedand sanitized by the sanitation crew.Theevaporatorfin
material shouldbe of a materialthat willwithstandcleaning and sanitizing
chemicalswithout corroding.
Everyplantshouldhaveaccess to an air testerto determinethe microbial
loadof the air entering the plant throughthe air-handling/filter systems.An air
tester is evenmoreimportantfor ready-to-eat product facilities. The air should
be testedfor microbial loads at leastonceor twice in the spring,summer, fall,
and winter. Whencheckingincomingair alwayslookon the roof to make sure
exhaust ventsare not directingthe exhaust air into the intakeventsor are upwind
of the intakevents. Wheninstalling new equipmentthat requires an exhaust
stack directthe installers to make sure thereare no intakeventsnear the exhaust.
Always contact a reputable HVAC engineerto assistin balancingthe air
within the plantand designingthe correctsizedair-handlingsystemfor the
plant's requirements.
7.9.7 Compressed air
Air compressors shouldbe the oillesstype.Evenif theyare ratedas oillessthe
linesshould be equippedwithcoalescing filtersand if usedfor product contact
or on foodcontactsurfaces theyshould be equippedwith high-efficiency
particulateair (HEPA)filtersratedat 99.97%efficiency at 1m. Compressed
air linescan contain condensate and becomea growthmedium for microbes.If
usedto create overrunin selected products or usedto openpackagingthe
compressed air can impart microbes, some pathogenic, intoor onto food
products and foodcontactsurfaces.
142 Handbookof hygiene controlin the foodindustry