What is considered the most inexpensive type of air filter?

The most inexpensive type of air filter is a miscus filter with oil on its surface. This type of filter utilizes a simple design and readily available materials, making it cost-effective for basic filtration needs. The oil on the surface helps to trap larger particles and dust, functioning effectively in an environment where precision is less critical.

In contrast, HEPA filters, while highly efficient in capturing small particles, are more expensive due to their complex manufacturing processes and materials. Carbon filters are designed to adsorb gases and odors, which increases their manufacturing costs and makes them less economical for general use. Electrostatic filters, which use an electrical charge to attract and capture particles, also tend to be pricier due to their technology and require maintenance to maintain their effectiveness. Therefore, the miscus filter with oil stands out as the most budget-friendly option for air filtration.