South Carolina executions have long been carried out by lethal injection, with the electric chair as an option if inmates so choose.

But two senators are proposing the Senate consider allowing nitrogen gas as a third option, one adopted last year by Oklahoma, because of the lack of lethal injection drugs available for executions nationwide.

This is not the gas formerly used in some states' gas chambers, which in some cases involved botched and gruesome executions. In theory nitrogen gas would slowly deprive an inmate of oxygen but not suffocate them.

Sen. Mike Fair, a Greenville Republican and chairman of the Senate Corrections and Penology Committee, has paired with Sen. Brad Hutto, an Orangeburg Democrat and defense lawyer, to propose using the gas as an alternative to a bill that would shield the identities of companies that sell lethal injection drugs to the state's prison agency.

That bill drew a 7-7 vote last year, preventing it from moving to the floor.

Fair said he plans to poll the bill out of committee Tuesday and propose the gas amendments to bypass the secrecy issue and give the Department of Corrections a working alternative once they are ordered to carry out an execution.

"We think we have an avenue," Fair told The Greenville News. "What we don't know is how well we are going to be received by either caucus."

Hutto said he is not a big fan of the death penalty, is not sure it is a deterrent but does understand from a victim's point of view that at least it stops that defendant from offending again.

"Having said all that, if we are going to have a death penalty, we need one that is being administered in a humane way without any legal issues," he said. "The way we are headed with this bill trying to let companies hide behind a shield, that is asking for more lawsuits and more trouble."

He said inmates could choose between gas or electrocution or lawmakers could do away with the electric chair.

Lethal injection has become an issue nationwide in recent years as companies have refused to provide the necessary drugs and pharmacists have balked at putting themselves into such a public crossfire.

As drug inventories expired, South Carolina's Department of Corrections has been unable to replace them.

Inmates can choose to be electrocuted but can't be forced to under state law.

So Fair and other lawmakers pushed a proposal to shield companies selling the drugs in hopes the secrecy would make them willing to provide the drugs.

But the proposal stalled in both chambers. Lawmakers since have proposed alternatives, including a firing squad or making electrocutions mandatory.

Fair and Hutto say the gas idea would be humane and could get lawmakers beyond arguments over secrecy.

While Oklahoma lawmakers adopted nitrogen hypoxia as a backup method of execution last year, it has yet to be used in an execution.

Lawmakers there envisioned a mask being placed over an inmate's head and pumped with the gas, which would not suffocate the inmate but gradually deprive them of oxygen, causing them first to lose consciousness and then to die, in theory without pain.

Another type of gas, from hydrogen cyanide, was long used by some states in gas chambers. But some of those executions resulted in gruesome deaths and many states mothballed the devices in favor of lethal injection.

Today, states are looking at alternatives to lethal injection unable to find the necessary drugs.

Oklahoma, where an inmate took 43 minutes to die after a lethal injection in 2014, also was in search of an alternate method when the idea of nitrogen gas surfaced. The drug is relatively cheap and readily available from industrial suppliers.

South Carolina last carried out an execution in 2011. Fair said the Attorney General's Office says the earliest an execution might again be carried out is later this year or early next year. Hutto said it could be several years.

In any case, Fair said the bill to shield drug companies likely will receive an objection, a move that would take a two-thirds vote to overcome. But he said the amendments would focus the issue on allowing the state's prison agency to carry out the law instead of on a debate over secrecy and transparency.

Hutto said he thinks the approach could work, though maybe not in this session.

"I think it has a better chance of passing than the bill they're trying to pass," he said.