Jay Lebo, who also worked as a regional operations manager at Ornge, told an all-party legislative committee that there were "a lot" of workplace injuries and he believed many of them were due to defective equipment.
"There really wasn't any appetite among senior management to do something (about) that," he said.
"So I think letting people work with equipment that you know is likely to cause injury is unethical."
He didn't elaborate on what kind of injuries were sustained or which equipment was defective.
Lebo, who also worked as Mazza's executive aide between 2008 and 2009, said it wasn't the first time he was asked to do something unethical or wrong.
Last week, he testified that he was asked by Mazza and Maria Renzella — former chief operating officer of Ornge Global, one of Ornge's for-profit spinoffs — to give auditors false information about expenses.
He wrote the business justifications for the expenses but didn't backdate them as instructed, Lebo said.
"It was the only time I was asked to do something illegal," he said Aug. 29. "It was not the only time I was asked to do something morally wrong."
Lebo joined other witnesses who have described Mazza as a volatile boss who wouldn't take no for an answer.
Mazza "built a team of people who would not disagree with him," he said. Anyone who did was "systematically eliminated from the organization."
Lebo said Mazza was concerned about keeping his salary under wraps. The committee has heard that the former CEO's salary increased exponentially during his time at Ornge, eventually reaching at least $1.4 million.
Usually, any public sector worker earning more than $100,000 would have to disclose the compensation publicly. But Ornge managers decided that they didn't have to disclose their salaries because they worked for Ornge's for-profit spinoffs.
"He wanted his salary to remain private," Lebo said. "He was a private individual. He felt that there were a lot of people out there who would be eager to get it, and the less information they had, the better."
Lebo said he earned $75,000 a year, plus a $15,000 bonus, as Mazza's executive aide. He was let go after two years at Ornge.
Premier Dalton McGuinty, who turned down a second request to appear before the committee, found himself under fire in the legislature as the Conservatives accused him of trying to obstruct its work.
McGuinty, his senior health policy adviser Sophia Ikura and government house leader John Milloy all refused to testify before the committee Wednesday, the Tories said.
None of the three offered an explanation for why they wouldn't appear, said Tory health critic Christine Elliott.
But McGuinty said Ikura is eight months pregnant and was at a doctor's appointment. He also denied that he was ordering her or any other government official not to appear before the committee.
"So I know (the Tories) like to see ghosts around all corners," he said in the legislature.
"But the fact of the matter is I think it's time to move beyond the games, beyond the partisanship, into the realm of public interest, which demands that we receive recommendations from the committee that we might carefully consider and that we might adopt so that we can bring greater oversight to bear over Ornge."
McGuinty has said he's willing to answer questions in the legislature and does not need to appear before the committee.
Milloy said he was given just 24 hours notice to appear and couldn't schedule it in. He added that he would have little to offer the committee, since he wasn't involved in the health ministry, which oversaw Ornge.
But their absence flies in the face of Liberal claims that they want to get to the bottom of the scandal that's plagued Ornge, Elliott said.
McGuinty keeps urging the committee to put forward recommendations, but it still doesn't know what the problem is, she said.
"There are far more questions than answers," Elliott said. "And I would suggest that the premier's part of the problem at this point, not part of the solution."
Ontario's auditor general has criticized the governing Liberals for failing to oversee Ornge, despite giving it $730 million over five years and allowing it to borrow another $300 million.
The committee has heard that the government failed to act despite numerous red flags that trouble was brewing at the organization.
Ornge, which receives $150 million a year from the province, is currently under a criminal probe for financial irregularities.
The committee has heard explosive testimony about an alleged kickback scheme, exorbitant salaries, badly designed medical interiors in brand-new helicopters and what one politician called "heavy-duty nepotism" at Ornge.
The province's chief coroner and a panel of experts are also taking another look at deaths involving Ornge over the past six years to determine whether transport may have played a role.