Because heat pumps operate by shifting temperatures, they naturally create condensation. This moisture makes the internal unit a breeding ground for mold, bacteria, and spores.
Even if the inside of the drum looks shiny, the exterior of the drum (the part you can’t see) is often coated in a thick layer of sludge, hair, and mold.
Lint is highly flammable. While you clean the lint filter, fine particles constantly bypass it and accumulate deep inside the chassis, near the heating element and motor.