BullMerde
Ex Mac Technician here....
1. Filters are not the answer: Filters get blocked, like fans, and would result in the machines over heating
2. There's normally 3 fans in an iMac: Power supply, HDD and CPU areas. There's normally no air gap between the display and outer screen, so highly unlikely this would be the cause. If you've ever repaired an iMac screen, you'll know how difficult it is to keep it dust free. Having an air gap would encourage dust...
3. I've pulled apart some disgusting machines: Most of those with display staining were due to smokers. Most of those with clogged fans on laptops used them on beds
4. Even with today's unrepairable laptops, it doesn't take much to take the back off and give the fans a quick blast with a can of compressed air.
Biting the hand that feeds IT
