Interpretation On
(Insect Light Traps)

September 3rd, 1987
Including the Oct. 30, '87 Update Letter

Public Health Service

Food and Drug Administration
Washington DC 20204

October 30, 1987

David W. Gilbert II
Vice President Research
Don Gilbert Industries, Inc.
5611 Krueger Drive
Jonesboro, AR 72401

Dear Mr. Gilbert:

After reviewing the 45-day data from USDA on mean daily catches of houseflies and stable flies in dairy barns, I believe you are correct that a statement in the 9/3/87 Interpretation on Devices for Electrocuting Flying Insects is likely to be misinterpreted. To correct this situation, the paragraph in question will be rewritten as follows:

"Light in the 330-350 nanometer (nm) wavelength seems to be most effective- in attracting houseflies, one of the primary target pests. Ultraviolet bulbs called 'black light' (BL) and 'black light blue' (BLB) emit light in the appropriate range of wavelengths. Electrocutors use BL or a combination of both types of ultraviolet bulbs since BLB bulbs alone have not proved to be as effective as BL bulbs in attracting houseflies and are considerably more expensive. Recent tests of bulb combinations have failed to show any significant difference between ......... using BL bulbs alone and .... using a combination of BL and BLB bulbs, in so far as effectiveness in attracting houseflies is concerned.

You may use this letter as a clarification to the 9/3/87 Interpretation. When the Interpretation is next reissued, this change will be incorporated.


Thomas L. Schwarz
Assistant Director for
Program Development
Retail Food Protection Branch
Center for Food Safety
and Applied Nutrition

Retail Food Protection
Program Information Manual
Part 6 - Inspection
Chapter 01 - Code Interpretation
Number 6 - 701
Date: 9/3/87

Subject: Insect and Rodent Control - Devices for Electrocuting Flying Insects

Applicable Codes/Sections
76 FSV 6-701, 2-201
78 FVD 4-301 (a), 2-201
82 FST 6-701, 2-201

This supersedes the Interpretation dated 8/11/86. Changes in the text are identified by asterisks in the margin; the format has been updated.


Are devices designed to electrocute flying insects effective and acceptable for use in retail food establishments?


Devices designed to electrocute flying insects can be effective against some pests of public health importance and are acceptable for use if they are positioned so that dead insects are prevented from falling on exposed food, food-contact surfaces, surfaces or clean equipment/utensils, and have "escape-resistant" trays which are emptied at least weekly.

Proper positioning of devices in areas where food and food-contact surfaces, equipment and utensils are exposed means:

  • Use of wall type devices only. Ceiling type units are not accepted in these areas.
  • Installed so that the center of the device is not more than 3 feet (=1 meter) above the floor.
  • * Installed no closer than 5 feet from exposed items. *

Center for Food Safety and Applied Nutrition,
Retail Food Protection Branch, HFF-342

Additional Regulatory Information

In addition to the public health concerns addressed in the model food codes, there are employee safety concerns about these pieces of equipment. Some of these are addressed in Title 29 Code of Federal Regulations (CFR) 1910.301 and 1910.304 and 1910.399 (Occupational Health and Safety Administration). Of particular note are requirements that:

  • arcing equipment be isolated from combustible material;
  • electrically charged parts be guarded in such a way that persons cannot be accidentally shocked when working near the unit if installed lower than 8'6" from the floor;
  • the device be properly guarded; and
  • * the equipment be accepted, certified, listed labeled or otherwise determined to be safe by a nationally recognized testing laboratory such as, but not limited to, Underwriter's Laboratories, Inc. and Factory Mutual Engineering Corp. *

Other concerns about employee safety have to do with human exposure to the radiation hazards of such equipment. Questions include whether the ultraviolet light could cause acute or chronic health problems to persons exposed to the device. Potential short term problems of concern would include skin burns. Questions about possible effects of long term exposure relate to premature skin aging, skin cancer and hazards to the eye such as the formation of cataracts.

FDA has measured ultraviolet radiation from a typical insect attracting device and has concluded that there is not a significant concern about acute health problems. The conclusion was based on Threshold Limit Values (TLV) of exposure as recommended by the American Conference of Governmental Industrial Hygenists (ACGIH) as presented and discussed by Phillips (1983). Questions about the health effects of long-term exposure are still unanswered. For this reason it might be prudent for operators to position these devices so that employees are not required to work continuously in close eye level proximity.


The model food sanitation codes require that "effective" measures be taken to minimize the presence of flies and other insects on the premises of a retail food establishment. At the same time food must be protected from potential contamination. To control insects without resorting to poison which can inadvertently contaminate food, pest control consultants are recommending installation of insect electrocutors. These devices contain an attracting light and an electric grid. Fluorescent or ultraviolet bulbs are used as the light source(s). Insects flying toward the light and between the grids cause a high-voltage, low amperage arc which electrocutes the insects.


* Light in the 330-350 nanometer (nm) wavelength seems to be the most effective in attracting houseflies, one of the primary target pests. Ultraviolet bulbs called "black light" (BL) and "black light blue" (BLB) emit light in the appropriate range of wavelengths. Electrocutors use BL or a combination of both types of ultraviolet bulbs since BLB bulbs alone have not proved to be as effective as BL bulbs in attracting houseflies and are considerably more expensive. (See Cover Letter above.) Recent tests of bulb combinations have failed to show any significant difference between ......... using BL bulbs alone and .... using a combination of BL and BLB bulbs, in so far as effectiveness in attracting houseflies is concerned.

Insect electrocutors are not a panacea. In fact, Lillie and Goddard noted that improper placement of electrocutors "may actually increase the problem with some insects." Rather, they should be considered as supplemental to good sanitation practices - effective exclusion (screening, properly installed air curtains and self-closing doors), effective cleaning of equipment surfaces and areas subject to food debris, and proper storage and disposal of garbage> *

It is important to realize that insect electrocutors are not effective for all insect pests and situations:


  1. Electrocutors are designed to control only certain types of adult flying insects. For example, cockroaches and several common stored-product pests such as the saw-toothed grain beetle and merchant grain beetle cannot be controlled by electrocutors because they do not routinely fly. Certain types of fruit and sewer flies are not attracted to these lights. Additionally, some stored-product pests such as the rice weevil are not attracted to light or to light of the particular wavelengths give off by the bulbs used in most electrocutors and therefore are not trapped.
  2. These units must be installed with particular regard to the flight patterns of the targeted insect. Houseflies, stable flies and blow flies, for instance, are found at lower levels. Traps for such insects are most effectively placed where the center of the trap is approximately 3 feet (= 1 meter) above the floor. However, the Mediterranean flour moth is more likely to be trapped near the ceiling. Thus, in storage situations where Mediterranean flour moths are the target insect, low traps would not be expected to work well.
  3. They must be adequate in number and size, and be efficient in design. Houseflies cannot be expected to respond to 15 watt bulbs from distances greater than 12 feet (= 4 meters). Therefore a single light cannot be expected to quickly eliminate the flies in a large area. The number of units needed will vary depending on electrocutor design - some are far less efficient than others in attracting flies. The lamp brightness, the size of the UV - reflecting area and even the orientation of the bulbs (horizontal or vertical) have bearing on efficiency.
  4. Insect electrocutor traps can be ineffective in areas with competing light sources. Daylight contains all wavelengths of light and can overwhelm light given off by electrocuting devices. insects are not attracted by a small wattage light source when inundated with light.
  5. Since the range of visual attraction of flies to lights is relatively short while the range of attraction to odors is relatively long, many more flies will be killed if the electrocutors are placed near sources of attractive odors (garbage areas) than if they are placed in odor-free areas.


Properly installed and maintained insect electrocutors can be effectively used with little concern in several areas of food establishments. These include receiving areas, corridors and refuse areas. The main concern related to acceptability involves the placement of the insect electrocutors within the food handling area. If improperly situated, dead insects could be impelled by the electric charge or simply fall or be blown from the device onto food, food preparation surfaces or clean food equipment/utensils. This could result in food being adulterated with dead insects or insect parts or possibly with viable microorganisms carried by the dead insects. Ceiling hung traps pose the greatest threat in that they spread insects the furthest. It is therefore important that the device be placed low and far enough from exposed items that dead insects will be of no concern.

An additional concern regarding acceptability is the maintenance of the devices. The dead insect carcasses in the catch tray of the electrocutor could become a food source for breeding Dermestids (larder beetles, museum beetles, carpet beetles). Also, eggs of dead insects may hatch and the larvae develop within an unemptied catch tray. Either of these scenarios would result in an ongoing insect infestation of the establishment unless the collection trays are cleaned frequently enough to interrupt the the reproduction cycle - at least weekly. By checking the identification of insects in catch trays, one can use the information to determine potential insect problems such as types of insects entering or establishing breeding populations within the establishment.


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