Filters prevent unwanted particles from entering the furnace. Unfortunately, as the particles accumulate, the filter becomes clogged, which is why it needs to be changed. The furnace will have to operate harder to pull the same amount of air through it by keeping the filter unchanged.
Despite its seemingly insignificant nature, the furnace's filter plays a critical role. You are at risk for poor air quality, costly furnace repair Livermore CA, and a possibly broken furnace if you refuse to install a filter on your furnace.