The Health and Safety Authority has launched an investigation into the chemical spill at the Chemifloc plant in Shannon, Co Clare.
Fire services and the company confirmed that a chemical reaction causing a gas emission occurred, when a batch of bleach was being loaded at the plant.
Seven workers were detained overnight in hospital and an eighth person presented at the Emergency Department in the early hours of this morning.
Those affected had to be decontaminated by fire personnel outside the hospital before they could be admitted.
None are believed to be seriously injured.
The Environmental Protection Agency has also launched its own investigation into the case.