pointof the waterjet on a surface,led to particularly largeincreasesin the
number of airborne droplets nearby.Figure 5.1 shows the particleconcentrations
measuredabout1 m fromthe various cleaningoperations,including the hose,
relative to a zerobackgroundcount.The hose led to around12 million particles
per cubicmetrewhereasthe concentrationsresultingfromthe other cleaning
operationswere around 20 times lower. All the cleaning operationsproduced
particles overa widesize range. withmostof the particles beingsmalland the
number decreasingwithsize:Fig. 5.2 showsthe trendfor a hose.
Burfoot and Brown(2004a) reporton the number of organismsin the air in
fourfood factory environments: high-risksandwich assemblyarea, chilled
dessert fillingarea, chilled pie and quicheproductionand a changingarea
connected to a high-care meatproduction room.The concentrationof airborne
organismsmeasuredin eachareavariedfrom42 mˇ^3 in the sandwich areato
2508 mˇ^3 in the changingarea.The number of particles containing an organism
relative to the totalnumberof particles variedfrom1 in 200 nearto staff during
hand-washing to 1 in 30 000 in periods of inactivity in a well-designed
productionarea.Thehighestconcentrationsof organismsand totalparticles
werefoundnearto cleaningoperations.The greatest ratiosof organismsto total
particles werefoundnextto cleaningoperationsand nextto staff.
5.4 Aerosoldispersal
Largeparticles, above 100 m, can settlenear to the cleaningoperation.Medium
sized particles maysettlenearto the cleaningoperationor evaporate to become
smaller particles, below 20 m, whichcan disperse easilyaround the production
area. The airborne particlesof most interestin chilledfoodfactories are those
Fig. 5.1 Concentrationof dropletsabove 1 m diametermeasuredin air around1 m
fromfour cleaningoperations(takenfromBurfootet al.(2003b)).96 Handbookof hygiene controlin the foodindustry