Uranium miner Energy Resources of Australia has confirmed four workers at its Ranger mine in the Northern Territory needed medical help after being exposed to chemicals during a shift.

ERA says an alarm went off at the mine on Tuesday and two workers immediately went into a decommissioned safe room.

But the ABC has been told by an anonymous source the room had clear signage saying it was an ammonia safe room.

When they went inside they were overcome by ammonia fumes.

The source says the men almost passed out and thought they were going to die.

ERA says the men were taken to the Jabiru clinic and have been given a health clearance.

Later that day, another two men working on a pipeline were sprayed with water contaminated with kerosene.

The company says they too have been given a health clearance but the ABC understands the two men initially failed a lung-capacity test and are on medication.

"ERA will continue its unrelenting commitment to the goal of zero injuries, and its focus on direct engagement with employees, to ensure all employees return home safe at the end of every shift," the company said.

Worksafe NT is on site investigating and says it would be inappropriate to comment.