recommendedas theyhavea whiterlightand low ultravioletemission, and use
less energythanothers.Low-pressuresodium lightsemitan orangelightthat
many find objectionable. Mercury vapor or incandescent lights shouldbe
installed at the entrance to the plantsite fromthe streetand/or in the parkinglots
because mercury vaporand incandescentlightsemitultravioletthat attracts
insects. Installingthese typesof lightsat the entrance to the plant site or in the
parkinglots will reduce the insect pressureon the plant, especially the loading
docks.
7.8.3 Air curtains
Air curtains, if designedand installedcorrectly, can help prevent flyinginsects
fromenteringthe facility. Thereare many homemadeversions,consistingof
ordinary fansblowingair out the opendoors. Thesedo not do the job.A
correctlydesignedair curtain should be positionedabovethe dooron the outside
wall.An exception can be madefor verylargerail or truckdockdoorswhere the
air curtaincan be installedvertically on eachsideof the doorwayblowing
outwards. The unitspositionedoverthe doorway mustbe clearacrossthe door.
The air column should be 3 inches (75 mm)thickand havea downand out
sweep.Probably the mostimportantcriterionis the velocity.The air curtain
shouldhavea minimumvelocity of 1600 feet (488m) per minute measured 3
feet (0.9 m) off the floor.For best resultsthe unit shouldbe hardwiredto the
dooropenerso when the doorstarts to open,the air curtainstartsand doesnot
shut off untilthe doorclosescompletely.For the few flyinginsectsthat do gain
entrance, a well-positioned insect electrocution light trapcan be installed.
Properpositioningwill ensure the unit cannotbe seenfromthe outside. Afterall,
the ultravioletlightsare designedto attract flyinginsects so theyshouldnot be
visiblefromopendoors. Theyare thereto attract insectsthat get insideonly.To
be the most effective the unitsshould be installedno more than5±6 feet (1.5±
1.8 m) off the floor. Ideallytheyshould be in a corner extending froma few
inchesoff the floorto aboutthe 5 foot (1.5 m) level. The trapswork by attracting
the insects to the light,whichis behind an electric grid.As the fly entersthe grid
it is electrocutedby the charge on the grid.Some regulatorsdo not wantthese
`zapper'typeunitsin foodprocessingrooms. Theirlogic is that the unit blasts
the insectinto many partsand there is morepotentialfor contamination fromthe
partsthanfromone intactinsect. A numberof vendorsof theseunitsare now
makingthemmorepassiveso they stun the insect and dropit wholeontoa sticky
boardlocated in the bottomof the unit.
7.9 Insidethe plant
Whensanitary design featuresare incorporatedinto a newstructureor into a
renovationor addition plan,theywill result in an improved appearanceof the
structure, and will reducethe timerequired for sanitation.Thiswill fulfillmany
Improvingbuildingdesign 133