The complaint said the latest incident occurred on Thursday when a worker employed by Contract Resources was allowed to enter into a mercury impacted vessel in the acid gas removal unit with inappropriate PPE.
The worker should have been wearing Level 3 PPE, which consists of a full air vest for cooling, chemical suit, fully taped gum boots with a breathing apparatus; however the complaint said he was only wearing Level 2, which consists of a normal Tyvek suit and respirator.
The complaint said the worker was in the vessel for around one and a half hours and mercury liquid had drenched through their suit to the skin. An ambulance was called and the worker's mercury readings were over 200 micrograms per litre.
The Offshore Alliance said it believed the worker may have been inexperienced and did not determine what level of PPE should have been worn before they entered the vessel.
"From this incident it appears that Chevron and Contract Resources Pty Ltd have put employees at risk by their own negligence to provide a safe working environment," it said.
WorkSafe confirmed to Energy News that it was investigating the incident.
It is the second incident involving mercury exposure on the island in the space of a week, after a worker was drenched in mercury and benzene liquid while cleaning a slug catcher on Friday.
Offshore Alliance told Energy News its members are now requiring the Department of Mines Industry Regulations and Safety to intervene "before there is a serious death on Barrow Island".
However, a Chevron spokesperson told Energy News that the workers involved in both incidents were well and healthy and have returned to their jobs.
"At this time, no adverse health effects from exposure to a hazardous substance have been recorded," the spokesperson said.
"While precautionary health monitoring is ongoing, personnel have resumed duties. Chevron Australia is committed to providing a safe working environment for its workforce."
The Offshore Alliance has long argued that majority of Contract Resources workforce are casual employees and have told the Union they fear for their jobs if they refuse to work under dangerous conditions.
"The Offshore Alliance believe that both Contract Resources and Chevron have breached their duty of care obligations to Contract Resources employees engaged on the Barrow Island facility," the complaint said.