A man has been airlifted to Liverpool Hospital in a critical condition after a tree fell on him during a workplace incident in Robertson just after midday.
Emergency services responded to reports a tree had collapsed on a man at Missingham Parade around 12.45pm.
An Ambulance NSW spokeswoman said four crews attended the scene, including an aeromedical crew.
The spokeswoman said the 37-year-old man had gone into cardiac arrest, and RFS personnel had performed CPR before paramedics arrived and took over.
The man was airlifted to Liverpool Hospital in a critical condition.
NSW Ambulance duty operations manager Gavin Wood said paramedics were faced with a number of challenges on arrival.
"When paramedics arrived they were faced with a complex scene, with a tree fallen on the man who had gone into cardiac arrest," he said.
"CPR was commenced by other emergency services, before paramedics arrived on scene.
"We were faced with a number of challenges to try provide the best care for the patient.
"These situations are extremely demanding for emergency services, we are did everything we could to provide the best possible outcome for the patient."