Peter Riggs and Tomislav Mandic were unaware a hose was pressurised and contained 98 per cent sulphuric acid when Mr Mandic disconnected it from a tank at a Hydromet waste treatment plant in March 2017.

Mr Mandic received second- and third-degree burns to about 10 per cent of his body including his arm, face, legs and eyelids, while Mr Riggs was burned on much of his left side, including an eyelid and wrist.

As he sentenced Hydromet and a company director for work safety breaches, NSW District Court Judge David Russell slammed authorities including SafeWork NSW and the NSW EPA for not detecting the Illawarra firm's "litany of failures".

Noting that NSW car drivers had to have their vehicle inspected each year and their eyesight checked at regular intervals, he questioned whether the state had any system of inspection and auditing of businesses licensed to handle dangerous chemicals.

"I do not understand why a business which handles extremely hazardous chemicals is given a licence and is then in effect left to police itself," he said, in a judgment published this month.

"If there is a system, why did it fail to detect the long-term failures of Hydromet?"

Judge Russell detailed how the hose wasn't suitable to carry 98 per cent sulphuric acid and a manager was unaware the plant even used such concentrated sulphuric acid.

Pipes weren't labelled, emergency drills hadn't been held for five years, training on the use of individual hazardous chemicals at the site was verbal on-the-job training and the company's safety manual was dated 2003.

Safety showers and eyewash stations - which the injured workers ran past after being sprayed - were not easily identifiable.

The men made it to the locker room about 50 metres away, where Mr Mandic's clothes "peeled off under the shower", the judge said.

"Any trained inspector who walked through the Hydromet premises would have spotted half the problems in the first hour," he said.

"The deficiencies in the documented safety systems would have become apparent in the second hour.

"The third hour could have been spent drafting criminal charges concerning Hydromet's egregious failures to observe its health and safety duty under the Act.

"Hydromet was guilty over a lengthy period of a litany of failures to fulfil its statutory obligations.

"Why did workers have to be seriously injured before that came to the notice of the authorities?"

Judge Russell found the level of culpability of both Hydromet and director Jeremy Perera fell in the high end of the mid-range.

He fined the company $225,000 and Mr Perera $45,000 after noting their guilty pleas in Sydney's Downing Centre District Court and their capacity to pay fines.

Australian Associated Press