Use fresh baking soda. Vacuum the carpet thoroughly, cover liberally with fresh soda, work in with a dry brush so that the soda penetrates deeply. If possible leave for 24 hours, then vacuum, once again, thoroughly. Baking soda is harmless to humans and their pets
you wash it????
Vinegar
stick an air freshener in the interior vent
Go to a professional cleaning supplier and ask them. They have the knowledge and the products to do the job.
"The musty smell of the attic filled my nostrils" BWHAHAHAHAHAHAH
The first step to getting a musty smell out of a closed up house is to open the windows. You will also want to burn some candles. Spraying Lysol will also help get rid of the musty smell.
The musty smell that Brian notices when he wakes up is caused by the dampness and mold growth in the shelter. The combination of moisture and lack of ventilation can create a musty odor.
Bleach
wash everything and febreze...
try using an air freshener
That musty smell could be coming from mold in the carpet and or it's padding, as basements tend to be damp. You could have the carpet cleaned professionally or clean it yourself with a good carpet cleaner. If this is unsuccessful it may be necessary to replace the carpet padding or both the carpet and it's padding.
A "musty" smell would describe a damp animal