We were called to this radio transmitter site because the transmitters were overheating. It was over 125 degrees inside the building when we opened the doors. This picture shows the fresh air input screens AFTER the first filter section to the building. Gee, I wonder why the transmitters were shutting down?
The screen on the left is the one we have mostly clean, the one on the right is how we found it after removing the filters. And yes, that is a dead animal in the lower left.
You wouldn't know it by looking at this picture, but that filter does have pleats in it! The shear amount of dust and dirt filled the pleats! To make things worse, this was one of the INSIDE filters after the outside filter and screens. How do you expect any fresh air to get into a building when you have filters that look like this? And they wondered why the transmitters were shutting down and the building temperature was hot.
Change your filters! They are inexpensive in comparison to replacing overheated PA tubes and electronics.