Very few pests sit out in the open on walls, ceilings and floors during daytime. The ones that do are easy to spot, so it can still be worthwhile to start looking here. Perhaps you can spot moth larvae heading up towards a place where they can pupate. On walls it is possible to find moth pupae and sleeping moths. On humid walls, where microscopic fungi exist, mites, booklice and plaster beetles live. If the walls are very damp it is possible that you will find slugs, woodlice and springtails on them.
You will rarely find pests in the middle of the floor during working hours, but if there is a layer of dust on the floor or other horizontal surfaces, one should not neglect to look for tracks in the dust.
If there is no dust, one could make use of the so-called flour method. In the evening, by means of a sieve, sprinkle a thin layer of flour or talcum onto the floor. It is then possible, the next morning, to see if there are any tracks from various pests from booklice to rats. Light the surface up from the side with a flashlight. This makes the tracks easier to spot. The pest is then, where the track ends. If it ends blindly, it must be attributed to a flying pest.
Many pests are shady and prefer narrow, inaccessible locations where debris accumulates and where it is sufficiently moist, dark and warm. This is typical for cockroaches and silverfish. Cracks in base shoes, loose panels, pipe penetrations, floor grits, the bottom of hoists and cavities in machines are classic finding places for that kind of pest. Otherwise the best chance of detecting them is to suddenly turn on the lights in the room at night. A certain element of surprise is always of value when it comes to pests that prefer the dark. It is often possible to catch pests when you look under and behind furniture that can easily be moved.
To draw out pests from their hiding an aerosol with pyrethrin is suitable. Spray it into cracks in such a way that the pests get confused and flee – hopefully – out in the open where you can see them.
You can also create locations, which are easy to control, that is, a kind of traps. When you put a moist, slightly crumpled bag on the floor and lift it with a brisk take one or two days later, there is potential for a catch.
Many insects are attracted to certain situations of light. This also applies to species that usually are active at night. You can often find them in windows or on the windowsill. Light fixtures are also obvious places to look for these pests. Many lamps work as traps for flying insects.
Light traps that are inspected regularly will reveal whether there are moths in the room. Trays with water containing detergent catch the insects that inadvertently land on the surface.
For fast-running insects like cockroaches, sticky traps are ideal. It can be cartons which are applied slow-drying glue on the inside. The insects that dare go into them get stuck and one can thus obtain a measure of how many there are and where they go.
Regular inspections should of course include searching for mouse and rat holes and droppings. A lamp with ultraviolet light can sometimes detect rodent urine and hair. Fresh urine fluoresce with a blue-white colour, old urine turns yellow. Hair from mice and rats fluoresce with a blue-white colour.
Traps containing feed for mice and rats can reveal whether there are rodents on the premises.