Three top nitrogen gas manufacturers in US bar products from use in executions

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.