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Controlling established pest infestations can often prove frustrating, time consuming, and costly to resolve. As the complexity of the infested building increases (from snack bar to school to city hospital, for example), so too can the level of effort needed to resolve whatever problem has arisen. Fortunately, there are often simple and cost effective means to prevent an indoor pest infestation from occurring. This article will help educate building managers on the preventative measures they can take to help inhibit pest problems from occurring in a facility.

In general, indoor pest infestations may be introduced to a building in a variety of ways. Shipments of infested materials and inadvertent employee interactions can contribute to a facility’s pest problem; however a majority of the pest activity inside a building has its beginnings immediately outside the structure. Pest exclusion, the method of keeping outdoor creatures outside where they belong, is a facility manager’s first means to pest prevention. That being said, the importance of factoring in environmental management can not be stressed enough. By eliminating the conditions necessary for a pest population to grow outside the building, facility managers can drastically reduce the susceptibility of a building to pest invasion. While the importance of these concepts cannot be exaggerated, they are all too often over- looked until after a problem has presented itself.

Below is a summary of the preventative methods that building managers should familiarize themselves with, as well as an in-depth look at the most common pests that create problems indoors for large facilities like schools, college dorms and hospitals.

Pest Exclusion
In basic terms, pest exclusion is simply preventing the entry of pests living outside your structure. In many cases, this is accomplished through some very simple and basic corrections. In other cases, however, the resolution can prove tricky without some knowledge of the pest(s) you are trying to keep out. Let’s examine a handful of the more common pests invading structures and address some potential exclusion techniques.

Rats and Mice
Before one can understand how to keep rats and mice out of a building, it is important to understand how little it takes for them to enter. Mice can utilize openings down to roughly a 1/4” in size to gain entrance into a building, while rats need openings about a 1/2”. There are many different types of openings to be considered. For example, a 1/2” gap under a door is a far different opening than a 1/2” diameter hole. If you were to make a circle with your thumb and forefinger in the diameter of a 1/2”, you could easily talk yourself out of believing that a decent sized rat could fit through, while fitting through the gap under the door appears to be much more valid. In fact, both are important. The 1/2” gap under the door is in fact one of the more common entry points that rodents utilize to enter structures. Because the gap extends the length of the door, it is not merely a 1/2” hole, but instead a “space” which they can squeeze under without much difficulty. I have seen rats, on a dead run, squeeze between gaps not much bigger than a 1/2” space when disturbed during an inspection. So, why worry about the 1/2” hole? The reason lies in the business end of the rat-his teeth. Rats and mice both have the ability to chew into and through a wide variety of household materials. If the rodent is interested in gaining access to the building, the 1/2” hole is enough space for it to push its muzzle into the opening far enough so that its teeth can gain access to the solid surface surrounding the hole. Depending on the surface’s material, generally the rat is required to do minimal work to expand the hole so that it is big enough to squeeze through.

How then can this be prevented? It starts with an inspection of the exterior of your facility. If the inspection is made with this awareness of pest invasion, it will become easier to identify potential entry points. Gaps under doors, as mentioned previously, are major contributors, but not the only points of entry. Holes around pipes that puncture the exterior walls (such as faucets or gas lines), missing vent screens leading into crawl spaces or attics, or damaged exterior surfaces may all be potential problems. We frequently see doors which are used to receive shipments being left open between shipments–an invitation to unwanted guests. Also, do not be fooled by the location of the openings you find. For example, you may ignore a 1” opening on the exterior of your building because it was located three feet off the ground. Rodents, especially rats, have several other physical abilities which allow them to gain access to just about any opening on your building, regardless of how high or low it is located.

Tools for performing exclusion will be discussed later, as they are typically consistent for all of the pests we will cover here. For now, let’s move on to another common pest.

Flying Insects
Like most rodent infestations, many of the flying insect problems we deal with in commercial facilities originate from outside of the structure. When dealing with flying insects, there are three basic areas of concern which should be examined.

First, check for proper screening of your facility, especially if opening windows is a common method of cooling off during warm periods. As screens age, they frequently fall into a state of disrepair and most flying insects can enter even a small opening of a structure. Also, screened doors and receiving areas should be checked, especially if those doors are on automatic closing devices–be sure these are still functioning properly.

Second, many commercial facilities have receiving doors which must be left open for extended periods of time. During shipments, for example, doors may be left open for hours. If this occurs during the daytime, when human traffic is constant, rodents are far less likely to gain access, but flying insects can easily enter. The use of air curtains have helped to reduce the level of flying insect access in similar situations. Air curtains are “sheets” of air being blown across an opening at a high enough volume that these insects are prevented from flying through. These sheets are created by wall mounted units hung above the door opening and are used commonly in warehouse settings, but are also available for regular doors. Installation of these units must be done according to instructions, as we often see them installed incorrectly, making them almost useless. In addition, when air curtains are mounted, they are no good unless they are actually on! It is common to find that employees have shut off these units due to the noise they create, or simply because they may blow a hat off.

Lastly, be aware of the lights on the exterior of your structure. There are many lights available now which are far less attractive to flying insects. Use of these bulbs may reduce the number of insects attracted to your building, thereby decreasing the number that can enter.

Large Crawling Insects
Included in this group would be creatures like cock-roaches, crickets, scorpions and spiders. As discussed above regarding rodents, a common entry point for these insects are the gaps under doors leading into our structures. Missing or damaged door sweeps or thresholds make passage from outside much too easy for these creatures. Other openings on the exterior of the building may allow access as well. For example, damaged stucco or exterior siding could be an entry point. For insects, this may result in an infestation establishing in the wall void which eventually makes its way into the interior of the structure. The interior of a wall void frequently  provides the ideal site wherein many insects live and reproduce–protection from predators, warmth and, occasionally, moisture. In some cases, you may not be limited to crawling insects, as bees, hornets and wasps also frequently use wall voids to build their nests in.

Tools and Solutions
Throughout the article there have been references to some simple methods of excluding pests from your structure. Following is a summary of those, as well as a few extra tips:
• Door sweeps and/or thresholds under ALL doors leading into your structure. This will help prevent rodents as well as crawling insects.
• Wire screening or mesh, ideally down to a 1/4” in size. This will prevent rodents from being able to get their gnawing teeth past your screen and chew it open. It will also be the right size to prevent many of the larger or flying insects from gaining access into your walls or attics.
• Steel or copper wool can be used to plug holes. These are frequently used temporarily until a more permanent fix can be made, but these materials have been known to hold up and prove effective for extended periods of time.
• Foaming materials may be used like the wools–they fill holes by expanding, drying and hardening to fit the hole in question. Again, best used as a temporary plug, but we have seen these used and left for extended periods. When used for rodent exclusion, it is wise to insert wire mesh back into the hole and foam around it.
• Facility lighting–reduce the attractiveness of your structure by utilizing new lighting options.
• Self-closing doors and screens can help reduce flying insect populations from entering your structure. Be sure all your screens are whole and undamaged.
• Proper repair of building exteriors is clearly the best long term solution–repairing damaged stucco or siding upon identifying it as a possible entry point. This may require a bit more time (and expense), and some of the other materials listed above may help close off the opening until this more permanent solution can be accomplished.
• Dryer vent covers can be purchased now with self closing flaps. Many indoor clothes dryers have vents which lead outdoors–all too often with the exposed opening outside serving as a perfect invitation for pests to enter. There are easy to install covers with hinges that allow the cover to open when the dryer is on and air is pushing through, and then close when the dryer is not in use. • Air curtains to assist in the reduction of flying insects when doors have to stay open.

Scott Crowley is the Technical Director for Lloyd Pest Control. If you want to contact him please send an e-mail to: scott.crowley@lloydpest.com.

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