The furnace filter is very important for the quality of the air you breathe and for the overall health of your HVAC system.
A dirty clogged filter alters the quality of air and puts pressure on the furnace because the air intake is proportionally reduced with the dirt accumulated in the filter – more dirt less air. This can damage your blower motor and the heat exchanger and you can waste hundreds of dollars in repairs and lost energy.
Every furnace has its specifications so using the recommended filter combined with good maintenance habits will save you money and time.
The big numbers you see on the filters packaging, 1000, 1200, 1500 represent the MPR – Microparticle Performance Rating. Higher that number gets, smaller the particles the filter retains are, but this is not always good because the air flow follows the same pattern, higher that number is, lower the air flow gets. So it is important to know what air flow your furnace needs and buy the filter accordingly.
The rule of the thumb is to change the furnace filter every 3 months. Below you can see the difference between a filter used for 3 months and a new one: