electronics and materials people - looking for waterproof yet air breathable material

I saw something a while ago in an electronics magazine that I can’t seem to track down now. It showed a picture of a fan blowing out air underwater. They were selling some sort of fabric that you could install over a fan vent that was weatherproof but still allowed airflow for cooling etc. Anybody seen or heard of this or know where I can find some? Muchas gracias,

Goretex and related products used in clothing are designed with pores that are too small to allow water vapor molecules to pass, but will allow the smaller air atoms/molecules to come in and out. Don’t know how they would work under water though as a completely different set of pressure systems are in play at the water-fabric-air boundary.

Sounds like Tyvek[sup]TM[/sup]. It sheds water, but passes air. I’ve never tried to use it in the manner described, so I can’t say definitively. Tyvek is available in several products, including the so-called “house wrap” and disposable coverall and labcoats.

Goretex will allow vapor, but won’t allow liquid water to pass. This is its advantage over plastic for rainwear. Plastic holds in the sweat and humidity, and after a while you are almost as wet from your sweat, as you would have been from the rain. Gortex allows the water vapor to pass, but keeps the liquid stuff out.

FTR Oxygen sensors used in some modern cars have a goretex membrane in them for just this reason.

Correct me if I’m wrong but I thought the point of Goretex was to pass water vapor but be a barrier to liquid water so that vapor from sweat would pass out of a rain garment while rainwater was kept outside.

I think the ad you saw was hyperbole. Any fabric which is tight enough to keep out liquid water isn’t going to allow enough air to pass to allow a fan to work.

You are correct. I mis-typed. “Water vapor” should have been simply “water”.