Some people don’t keep air filters in their central heating and air conditioning system.
While this can work for a little while it is very dangerous in terms of your heat and a/c system breaking for good.
Also, when you do not have an air filter in your central heating and air conditioning system the heating and the cooling comes out rather dry and sometimes way too strong. It’s bad for your skin and your health. How do I know all this? Because one time I went without an air filter for an entire month and it really made the air quality in my home pretty bad. Also I ended up having my entire central heating and air conditioning system break down. It was sheer luck that it was able to be fixed. But as a result I also had to have my ductwork deep cleaned because of all the dirt and grime that got in there from that whole month. It was something that I will never even attempt again. I do not want the bad air quality or my central heat and a/c unit breaking down. Plus my skin was so dry I felt extra horrible. So the whole point of this story is to say that you should always have an air filter in your central heating and air conditioning system. No matter what. Even if you do not remember to change the air filter one month, it will not do as much damage as having no air filter at all!