After authorizing a strike two weeks earlier, the US Teamsters union local 100 in Cincinnati, Ohio, carried through with a 24-hour work stoppage at US industrial gases producer Airgas on Mar. 11.

It was the local’s first strike since 1999.

The workers said Airgas violated US labor laws, in the first place by disciplining an employee, a union steward, if he attended negotiations on a new contract. The last agreement ended on Nov. 30, 2015, and a new contract has not been signed since French gases producer Air Liquide in November sealed a deal to acquire its US rival for $13.4 billion.

“Negotiating a contract is the basic right of workers' unions. It's completely unacceptable for the company to threaten workers for exercising their rights. The company also acted illegally when it unilaterally terminated workers' 401(k) retirement funds,” the Teamsters local said in a statement.

Some 20 Airgas employees are said to be protesting the company’s proposals for a new contract they claim would destroy job security and seniority as well as remove the workers' legal rights to honor picket lines.

The US employees are especially angry that Air Liquide has not intervened in their dispute with Airgas, which they charge has been “abusing workers across America” by locking them out during contract negotiations, threatening them with loss of health care benefits and wages and attempting to break the union by illegally threatening activists.

"This would never happen in Air Liquide’s European operations," said Keith Gleason, Teamsters Tankhaul division director, adding that the French company “has stood idly by and allowed these attacks on its American workers to continue.”

A spokesperson for Airgas told the newspaper Cincinnati Enquirer the company believes the union’s efforts to involve Air Liquide in this dispute are “unlawful,” and allegations it has violated employees’ rights “baseless."

On March 4, Airgas filed an unfair practice charge against Teamsters Local 100 for engaging in “bad faith bargaining.”

The problem at Airgas extends across North America and is putting its business at risk, including current and future pipeline projects, the union asserts.