TIL: You Can Smell Through Your Skin | Today I Learned

[Music] Your nose isn't the only thing that can smell things. You can smell through your skin, and that was a big surprise on one of our expeditions. I dive into a lot of these underwater caves, what we call blue holes. Maybe at about 30 ft, you hit these wild looking colors; that's actually the pigments in the cells of individual bacteria.

And you start smelling something. Well, you're smelling hydrogen sulfide gas. [Music] It's that same rotten egg smell that you get out of sulfurous springs that in high concentrations is extremely toxic. You have a regulator in your mouth, you're wearing a mask, so it's not coming in your nose. You're not breathing it in, yet you're smelling hydrogen sulfide, and it's actually going through the pores in your skin.

[Music] [Applause] If you end up spending enough time in it, you stop smelling it. It actually deadens the olfactory nerves, and that's a sign we use to ourselves that we've been in it too long. Get through it or come up.

These animals live in our buildings. They get on our roofs; they even go into the sewer system to get away from traffic and people and can move for considerable distances using those tunnels.