Nitrogen Asphyxiation
Three employees working in a windowless room at a facility I worked at died this way. They were unaware there was a nitrogen leak. No symptoms at all, apparently.
I suspect, though, that there must be some legal reason that executions are carried out the way they are. Any lawyer types out there who can explain why theres a dearth of options?
Oh I can answer that. In most states that have capital punishment, the method(s) of execution are prescribed by law. Now as to why the legislators do not accept other forms of execution such as Nitrogen Asphyxiation ... I attribute that to a lack of awareness or education on the part of the legislators.