The most common and economically important cockroach is the German Cockroach. Like Bed bugs, German Cockroaches are hitchhikers and are carried in on items from outside the home or business. In restaurants, they usually come in with stock from vendors or employees that have a problem at home. Cockroaches need 3 things for survival; food, moisture and warmth. If these conditions exist they will thrive and breed into an "infestation". It is a misconception that "if you see one you have thousands". This was probably propagated by the old TV commercials for the over-the-counter sprays.
Unless poor sanitary conditions exists, it is unlikely you have an infestation. I have had calls where an employee see's a cockroach at their desk and the property manger wants the whole office building floor fogged immediately. This is not necessary as the cockroach most likely came from a lunch delivery or from an employee shopping on their lunch break.
In some instances a heavy "infestation" from a neighbor may spill over into adjacent rooms, suites or apartments. This is normally determined by a thorough inspection to determine the source and likely conditions sustaining the "infestation". Reoccurring sightings will happen until the source is found and eliminated.
Some customers request "Bombing" for a cockroach problem. This is occasionally confused with "fumigating". Fumigation is a gas that is used for very specific treatments of dry-wood termites, commodities such as bulk coffee and grains and other specialty pest control jobs. Fumigation is not used for General Household Pests like cockroaches. The correct term is Fogging. Fogging is an Ultra Low Volume (ULV) treatment that can penetrate deep into voids of kitchen equipment and walls to flush out cockroaches that are hiding in hard to get to locations. The material is very expensive and has little to no residual effect to continue killing. A professional with proper training will use this method only in specific circumstances that require a more aggressive approach but is rarely used in homes or offices. It is mostly used in restaurants and requires extensive preparations to protect food and food preparation surfaces.
So what works?- There are many cockroach baits on the market that are extremely effective. These are generally low toxic gel baits that when applied correctly attract cockroaches that eat it and die. Most bait aversion problems reported as " bait not working" is due to lack of experience or improper baiting. When used properly and through consistent follow up treatments/inspections, bait is the least risk and most effective treatment for cockroaches.
Sanitation is key! It cannot be stressed enough that cleaning is the ultimate solutions to eliminating the risk of German Cockroach “infestations”. While we are all at risk of having a cockroach introduced into our home or work environment, if the conditions are not suitable, they can quickly be eliminated. So much for the “hardiest most persistent pest that will out live us all even after a nuclear blast”. Through good housekeeping practices and diligence, it is absolutely possible to maintain a cockroach free work place and home.