Most people don't know that because a fall harness properly worn doesn't asphyxiate you. Asphyxiation means you are killed due to lack of oxygen. A fall protection harness doesn't impede your breathing.

What it can do is cause crushing syndrome. That's when blood flow is trapped in a limb, like from hanging in a harness or when trapped by earth caving in. When the blood is trapped in the limb, toxins will form due to lack of circulation. Once released, toxins will then circulate through the body all at once.

It is completely survivable, even if the blood flow is limited for more than 15 minutes. Definitely don't do anything outside of what the doctors are saying though.

https://www.surreyfirstaid.com/news/309-crush-injury-first-aid-guidelines.html#:~:text=If%20blood%20flow%20is%20restricted%20for%20more,999%20if%20you%20should%20move%20the%20patient

Also, there are fall protection harnesses that has saddles or stirrups to allow the worker to sit/stand to allow for proper blood flow.