Fourteen people were treated by Calais Regional Hospital, with all but one of them expected to be released by Thursday night.
The incident happened during a planned maintenance outage at the Woodland Pulp Mill. According to officials at the mill, employees were exposed to gas because of a lack of ventilation.
"Fortunately, we were able to isolate the situation and stop the release of the chlorine dioxide gas rather quickly but not before we had an impact on some of our contractors," says Scott Beal, the communications manager for Woodland Pulp.
Calais Regional Hospital actually held an emergency response drill with the mill in October 2015. For them, this went as smoothly as they could have hoped.
"It went off very well. I was very pleased with the response of our staff because it takes a lot of people from our ED nurses and providers to our area ambulance and emergency response crews to environmental services and maintenance and security. Everybody kinda has a role. They all pitch in to get it done," says Dee Dee Travis, VP for community relations at Calais Regional Hospital.
The mill is currently working with OSHA and the Maine Department of Environmental Protection.