Whether it is TCP, a derivative or something harmless, the smell known as "wet sock smell" or "damp dog smell" is very very very similar to the smell of valerian acid, an oil based chemical used as esters to produce perfume.
If the smell is considered normal by some, can anyone explain to me quite simply How this oil based chemical enters the airconditioning system and why it's usually starting to happen around 5 minutes after T/D.?
I think if an airliner patents a new airconditioning system that's able to filter whatever compound that causes this will see a huge profit increase.