This will probably help make more folks aware of relative risk.

Since I have a pit I can work on the bus whether it is up, down or at ride height. Theoretically I do not have to block the bus up in the air. If anyone ever watches a grease monkey at a truck stop you will never see him block a bus or truck when he lubes it. He has some degree of risk.

The risk of an air bag failing catastrophically is slim. But when my bus is going to get worked on from the underside, I raise it fully and support it under the body support points because sometimes I am putting my arms or body between pinch points such as between an axle and the underside of the body. I don't care how small the risk. I do not want to take a chance of getting crushed.

Greg is right about ramps providing space so the bus cannot crush you, but that only applies if you never put yourself or any part of your body between the underside of the shell and any suspension member such as an axle, subframe, radius rod, etc.