Thanks for contacting me.  This is a very frustrating problem and fairly common.  In fact, we had the same issue last fall.  It sounds as if something has died in the interior walls of your house or possibly the attic.  It could be a mouse, rat or something even bigger.  Since you can't locate the source (and even if you did, removal might not be possible due to the location), about the only thing you can do is to keep up with the charcoal products.  Since the weather has cooled down, you might want to open the windows as much as possible to air out your house.  If allergies are a problem, opening the windows might not be possible.  Maybe you could just open them in the room that's most affected and  keep the doors to that room closed from the rest of the house.

The good news is that the odor will usually go away within a week or two, depending on the size of the animal.  We never did find the source of our odor but after a week, it was less noticeable and was gone in 2 1/2 weeks. 

Sorry I couldn't be more help.  Please contact us any time we may be of assistance. 

Carrie