Duggan said the injured man must have done "something stupid that no one saw to get that tool in his eye".
"I think it was a safe environment. I haven't changed anything I do ... I still deglaze windows and do not wear safety glasses, but would make sure (workers) wear them."
The incident happened as Duggan and his employee were on the third storey of scaffolding removing window panes from Tauranga Boys College gym in May last year.
The Department of Labour said Duggan taught his employee to remove rubber seals using a screwdriver but gave him a chisel for the task when they were working at the gym.
The court heard that as the man tried to remove the seals he slipped and the chisel hit his eye.
The department's Ona De Rooy said an investigation found a few simple measures could have reduced the potential for harm significantly.
"It is unacceptable that Mr Duggan failed to adequately prepare his employee to carry out this work. A safe procedure for removing seals from window frames should have been established, appropriate tools such as a specific pry tool or putty knife should have been used and protective eyewear should have been worn. This would have prevented an accident such as this from happening."
