[marceldegraaf]

It's due to the narcotic effects of nitrogen that GUE (Global Underwater Explorers, a diving association rooted in tech/cave diving) uses EAN32 (32% oxygen) as their standard breathing gas.

They're also more conservative in their recreational diving depths: 30m (100ft) is the recreational limit, beyond that technical certification and a helium-based breathing gas (e.g. Trimix) are required.

[nradov]

I think you misunderstood the GUE standards. Nitrox isn't significant less narcotic than air. They set a 100 ft equivalent narcotic depth maximum limit somewhat arbitrarily because empirically that seems to be pretty safe. Below that depth we add progressively more helium to the mix to limit narcosis as well as gas density (work of breathing).