I am sure my hair isn't porous because my hair has all the other characteristics of low-porosity hair. It resists chemical treatment (it doesn't absorb hair color well, and I had a perm once that fell out within a week). It gets very easily weighed down as well. I even did the float test--my strand of hair NEVER sank to the bottom after a very long wait. I think it has a fast drying time because it never absorbs the water to begin with. I also have very thin hair--less hair, less drying time.