Gloveboxes are onlynecessary, of course, if people are involvedin the food
production line.If robotsundertookproduct manipulation, therewouldbe less
microbiological risk and the whole room could be temperature and
atmospherically controlled!
Where the use of gloveboxesis impractical, partialenclosure of the product
can be achievedby the use of localised,filteredair flows. The high-riskair-
handling systemprovidescontrolof airborne contaminationexternal to highrisk
but provides only partial control of aerosols, generated from personnel,
production and cleaning activities,in highrisk.At best, it is possibleto design
an air-handlingsystemthat minimises the spreadof contaminationgenerated
within highrisk fromdirectlymovingoverproduct. Localisedairflows are thus
designedto:
∑ Provide highlyfiltered(H11-12)air directlyoveror surrounding product, and
its associatedequipment. The air is generatedinto a box whichhas a top and
sides that directthe air downwards, and a floorthat collects the air and wastes
or recycles it. In somecasesthe `base'of the box maybe missingand the air
is directed to waste.
∑ Provide a degree of product isolation rangingfrom partialenclosure in
tunnels to chilled conveyor wells,where the flowof the filteredair providesa
barrier that resiststhe penetration of aerosol particles, someof whichwould
contain viablemicroorganisms.
By chillingthe air, it is possibleto keepchilledproduct cold whileoperatingthe
high-risk area at ambient conditions.Economically,it is also veryexpensive to
coolthe whole of the high-risk areadownsimply to maintainlow product
temperatures,thuslocalisedchillingcouldbothcut costsand enhanceproduct
safety. Evenat the lowestlevelof productenclosure, localisedair conveyor
wells (Fig.8.3),a 1±2 log reduction of microorganismsfromthe surrounding air
can be demonstrated withinthe protectedconveyor zone(Burfootet al., 2001).
Fig. 8.3 Chilledair is suppliedfromair ductson eitherside of a productconveyor.The
chilledair retainsthe producttemperatureand its movement,spillingoverthe duct
surfaces,providesa barrierto microorganismpenetration.166 Handbookof hygiene controlin the foodindustry