New Porch has smell from air brick

Hi, the air brick should not be internal, the builder should have made a vent pipe to the new exterior wall of the porch or blocked the air brick up, providing there was other air bricks around the property. However my Conclusion is, newer Properties tend to be built on concrete beam & blocks the voids underneath the floor are very wet and usually smelly so block the air brick in the porch job done. But if the property is older and has a timber suspended floor I would have somebody out to investigate no obvious problems. This could be dead vermin or even a leaking sewer pipe? An experienced builder should be able to identify your problem or conduct a process of elimination for you. I wish you well, Good luck! Kind regards Dean @ AllSpace Build