A Canadian company is facing criticism for allegedly supplying the equipment for a state execution in the United States, in a case that has drawn outrage for the reliance on a seemingly untested method of execution. On Thursday, Alabama plans to kill inmate Kenneth Smith by suffocating him with nitrogen gas, a method never before used in the country. The US-based advocacy group Worth Rises and the Responsible Business Initiative for Justice says that in the execution, Alabama will use workplace safety equipment made by the subsidiary of a Canadian company. The state’s department of corrections would fix Smith to a gurney, apply a respirator mask to his face, forcing him to breathe pure nitrogen and causing death from oxygen deprivation. The mask and hose used for the execution are allegedly manufactured by Allegro Industries. The group says Allegro is a subsidiary of Quebec-based Walter Surface Technologies, which in turn is partly owned by the Toronto private equity firm Onex Corp – a company that also owns one of Canada’s largest airlines. Allegro Industries, Walter Surface Technologies and Onex Corp did not immediately respond to a request for comment. Smith was sentenced to death for the 1988 stabbing of Elizabeth Sennett in a murder-for-hire plot. Her husband, pastor Charles Sennett, paid Smith and another man $1,000 each for the killing, then later took his own life. A jury voted 11 to 1 to give Smith a life sentence, declining to send him to death row, but the trial judge overturned their decision and ordered his execution. Alabama attempted to execute him last year, but he survived the botched execution by lethal injection after officials failed to find a vein. Last week, a federal judge gave the green light for a new execution to go ahead, using nitrogen gas. The method, which causes death by nitrogen hypoxia, involves forcing the condemned prisoner to breathe only nitrogen, which deprives them of oxygen. But the method of execution is considered experimental, and veterinarians in the US and across Europe have deemed it unacceptable as a form of euthanasia for most animals. Earlier this month, the United Nations human rights office warned this method of execution is untested and may cause serious pain. Pharmaceutical companies are increasingly banning the use of their products for executions, making it difficult for states that still have the death penalty to source the chemicals needed for lethal injection. Both Oklahoma and Mississippi have also permitted the use of nitrogen hypoxia as a method of execution. In recent years, activist groups have targeted Canadian investment in the US prison system. In 2018, the Guardian and Documented reported that the Canada Pension Plan Investment Board (CPPIB) – which manages $366.6bn in pension funds on behalf of about 20 million Canadian retirees – holds stock in Geo Group, a company which operates private prisons in the United States. The pension later divested of the investment, which at one point totaled $6.1m.