areait is recommended that a goodsealerbe applied to the interiorconcrete.
This willprevent moisturemigrationintothe doubletee concrete and the
ultimate rusting of the reinforcement rodsin the concrete. It will also eliminate
dusting fromthe exposed concrete and createa smoothersurface. Once the
reinforcementrod startsrusting, it will causeexpansion of the rods and cracking
and chippingof the surrounding concrete, creating a potentialphysicalhazard
for the products beingproduced below.Thisconditioncan be veryexpensive to
repair and can be preventedby the application of a sealerat the outset.Rusting
of the rebarand the cracking of the surroundingconcrete can affect the structural
integrity of the double tee roof.
Exposedstructural steel usedin ceiling/roofconstruction shouldbe encased
in concrete or its equivalent. Encasing structuralmembers with concrete
sometimesaddsa prohibitive load on the roof structure, especially if utilities and
equipmentare to be hungfromthe ceilingor air-handlingequipment is to be
placed on the roof. There are, on the markettoday, techniquesfor boxing in
overhead beams,steeltrusses,and otherstructural members withfoamsheets
and thensprayingon a fiberglassresinsurface. Thiscreatesa smoothseamless
surface that willwithstandmoisture and chemicals, and sealsthe structural
members fromcollecting dust, moisture, and debris,whichcan fall ontothe
product below.
Somewarehouses use drywall or gypsumceilings.Thesemayworkfor dry
areas but should not be usedin wet environments.Materials suchas corrugated
metaland metalpan roofing are not recommendedfor foodprocessingareas
owingto the highrate of heattransfer that can causecondensationproblems.
Suspended ceilingsutilizing 2 4 sq. foot (0.61.2 m^2 ) panels suspendedin
an aluminumor stainlessgrid are not recommended for processareas. Thereare
a numberof disadvantages to thesetypes of ceiling.The panelsare oftenclipped
downor caulked in place when the ceilingis newlyinstalled.Then,whenever
any workhas to be doneon pipelines,etc., that are abovethe ceiling,a panelhas
to be displaced.Suspended ceilingsusually do not lendthemselvesto load
bearing, so anythingabovethe ceilinghas to be accessedthroughthe ceiling
itself. Whenany workis completed,it is virtuallyimpossible to replacea panel
and secureit as it was originally.Thesepanelswill warp,and any air pressure
changes caused by opening or closing doorswill createmovement in the panels.
Often panels get broken or the grid frames bent and this allows air frombelow to
mix and contaminatethe air abovethe ceiling,and the air fromaboveto mix
withand contaminatethe air below in the processroom.It is difficult to treatthe
aboveceilingspacefor insects sinceit is not a load-bearingsurface. Suspended
ceilings,if used,shouldbe confinedto officespaces, laboratories or other non-
foodproductionareas.
7.9.6 HeatingVentilation Air Conditioning(HVAC) systems
The Foodand Drug Administration (FDA,2003) statedin a presentation:
`Airbornecontaminationis stronglysuspected as the causeof some pathogenic
140 Handbookof hygiene controlin the foodindustry