Meanwhile, Emergency responders were called to the scene for a report about a "chemical reaction in the kitchen area" and arrived at the just after 5:30 p.m. Another employee tried to clean up the substance with a squeegee but was overcome by the fumes, Patterson said.
The two managers have been fired and the regular customers that made the request have been banned from the chain.
The CDC advises anyone who comes in contact with chlorine gas to leave the area where it was released and get fresh air.
Ryan Baldera, a 32-year-old employee, was transported by ambulance to Lahey Hospital where he passed away as a result of his injuries, the statement said.More news: Supreme Court to pronounce verdict on Ayodhya dispute tomorrow
They identified the noxious chemical as sodium hypochlorite-a household bleach compound that has been used since the 18th century. Four or five of them were held overnight, according to Burlington assistant fire chief Michael Patterson.
The man, who has not yet been named, was rushed to a hospital, where he later died.
Firefighters evacuated the suburban Boston restaurant and called for a Tier 1 hazardous material response.
Ten other people at the restaurant - eight employees and two customers - checked themselves in to hospitals Thursday, with symptoms including breathing difficulties, watery and runny eyes, and shortness of breath, Patterson said.More news: Disney+ launch date for United Kingdom and Ireland confirmed
On Wednesday, staff at a Buffalo Wild Wings in a strip mall in Naperville, Illinois, ordered a mostly African American group of customers to switch tables because another patron did not want to sit next to black people.
A Buffalo Wild Wings statement says the company is "shocked and saddened" and working with the franchisee and authorities. "For some reason tonight, there was just a reaction that led to this". Authorities are urging anyone else who was in the restaurant at the time and believes they may have been impacted to seek medical treatment.
The restaurant will remain closed while the investigation continues. Workplaces that use hazardous chemicals are required to train employees on potential hazards, according to the federal Occupational Safety and Health Administration (OSHA), which is investigating the incident at Buffalo Wild Wings.
"This is a product that we've been told is a common product used in floor cleaning", Patterson said.More news: Possible chemical culprit found in vaping illness outbreak