Foodworker is quite right there are many different theories where to place EFK`s in a food environment, no real scientific data has been gathered on this particular subject. So you have to rely on experience and general common sense.
The only definative work I know of was by Moray Anderson PHD in the sixties/seventies and that was on the uv light length frequencies needed to draw in as large a population of flying insects as possible into a killer unit.
Still did`nt get them all as the common house fly Fannia canicularis stubbornly refuses to be drawn into a fly killer unit and the only method of control for them is exclusion.
Here are the key rules I work to when placing EFK`s and deciding which model to employ/recommend..
1, use the correct unit with the correct UV output for the area (M2) to be covered, it is a pointless excercise in trying to achieve a satisfactory flying insect catch if the units do not have enough UV output to lure insects into them. There are sufficient guides available to help either the quality control manager with their pest controller to get that part right. Why move units around the premises?, if you use the correct units to manage the square footage and site the units correctly there is absolutely no need,
2, Use the correct unit for the situation, if there is insufficient room in the premises and the EFK`s are within 2 metres of either production, mixing, finishing or storage, to avoid potential non-conformities via physical contamination then sticky board fly killers are really the only option. The models available are now much improved in the last 5 years since demand for them has risen, and in my kosher and halal clients premises they are the only models I will recommend. Their only minor drawback is the continued cost of replacement boards which must be passed onto the client.
3, Placement, this is an issue, yes by a doorway is good if the door is kept closed when not in use, EFK`s are in direct competition with natural UV light during daylight hours and their efficacy is compromised. There is also the issue that if placed by windows and doors during the hours of darkness the same EFK`s will also draw nocturnal flying insects to the building and if the windows are not screened into the production areas.
So their placement must be made with all those aspects in mind and also do you have to call in an electrician to install them where they are to be situated. Best practice states that 2m is the optimum height for placement, but I have some units in a large oriental food importers warehouse at 10m by necessity and I still achieve good catch rates and samples. So make of that what you will.
4, Last but not least, annual servicing and UV tube replacement, UV tubes in EFK degrade with a marked peak and trough over a period of between 6-9 month dependant on the quality of manufacture. As we are a temperate climate that means that we generally only require UV tube replacements once a year in spring to make sure that the tubes are at their peak during the summer season. Ensure that all your units are serviced regularly and the tubes changed annually to guarantee their efficacy, but in more tropical climates I would have thought that UV tubes would be best replaced every 6 months.
Catch tray analysis? if you have high numbers that means you have a problem with them entering the premises in the first place, look on the other threads with regard to ERD, exclusion is the key, keep them out is the first order of the day.
I tend to use catch tray analysis to indicate trends, high numbers of specific species in a catch tray or on a sticky board will indicate there is a specific problem and requires investigation, the species presented will tell you the potential breeding material and possible harbourage, these things can all be deduced from a simple catch tray.
As with all these thing they are easy when you know how 
Bunny 
