Descent Rate Limitation of 75 ft/min

[Brewone0to]

This is what I had always heard was the hazard.
Although I don't think it is only with helium gas.
Helium likely just makes it more pronounced because of it's rapid upgas/offgas rates.

 

[mopardiver]

Here’s the way I look at it

Spending time on wrecks is really awesome
Spending time in open water above the wreck is not as awesome
Time equals air consumption…and I do dive singles

However, after enjoying the wreck, I do use a safe ascent rate and usually do a one minute deep stop in addition to a 5 minute safety stop.

 

[ajduplessis]

On deep dives we regulary hit 160-180 fpm, however you need to slow it down past 400 feet as HPNS will effect your vision, cause nausea, dizziness and tremors. I have only seen issues with vision (can't read Petrel) and likely decreased awareness. HPNS and narcosis effect divers in different ways.

The shot is that descent rate is a non-event above 400ft, however you need to take care of your ears, be sure you know the site you dive and be considerate to your buddy if you plan on dropping like a stone.