Which air filter type is typically made of electrostatically charged fibers?

Electrostatic filters are specifically designed using electrostatically charged fibers, which serve to attract and capture particles from the air. This unique characteristic allows these filters to be more efficient at filtering out a variety of airborne contaminants, including dust, pollen, and smoke, due to the static charge enhancing particle adhesion. The charge effectively increases the surface area for trapping particles, leading to improved filtration performance.

In contrast, HEPA filters are known for their mechanical filtration capabilities, capturing particles of a specific size through a dense mat of fibers, but they do not rely on electrostatic charge for their operation. Activated carbon filters utilize carbon to absorb gases and odors, and while they play a critical role in improving indoor air quality, they are not made of charged fibers. Fiberglass filters are predominantly used for larger particles and lack the electrostatic properties that enhance filtration efficiency.

Thus, the distinctive feature of electrostatic filters being made of charged fibers clearly differentiates them from the other types of filters presented.