Move follows Alabama’s recent killing of death row inmate Kenneth Smith using previously untested method

Three of the largest manufacturers of medical-grade nitrogen gas in the US have barred their products from being used in executions, following Alabama’s recent killing of the death row inmate Kenneth Smith using a previously untested method known as nitrogen hypoxia.

The three companies have confirmed to the Guardian that they have put in place mechanisms that will prevent their nitrogen cylinders falling into the hands of departments of correction in death penalty states. The move by the trio marks the first signs of corporate action to stop medical nitrogen, which is designed to preserve life, being used for the exact opposite – killing people.

The green shoots of a corporate blockade for nitrogen echoes the almost total boycott that is now in place for medical drugs used in lethal injections. That boycott has made it so difficult for death penalty states to procure drugs such as pentobarbital and midazolam that a growing number are turning to nitrogen as an alternative killing technique.

Now, nitrogen producers are engaging in their own efforts to prevent the abuse of their products. The march has been led by Airgas, which is owned by the French multinational Air Liquide.