Where is my Furnace Filter Located
To find out where you furnace filter is located you can look somewhere before the fan. The filter is located upstream of the air handler in the duct system. You can find more information here: http://www.furnacefiltercare.com/whereismyfurnacefilter.php
When it comes to your furnace filter, you need to know where it's located so that you can regularly change it. Normally, it is located in the area that is upstream to the fan, and is sometimes hidden very well.