Hicksville firefighters rushed to 65 Broadway after they received a call for an unconscious person.

When they got there, around 11:30 a.m. Monday, workers were carrying a man from the second floor to the first floor, said Chief Joe DiFronzo. That’s when the chief said he learned there were high carbon monoxide readings in the building.

Oxygen was administered to the man.

A total of four people were taken to the hospital.

“Carbon monoxide is not a good thing. It’s odorless. It builds from the ground level up. It’s a very silent killer,” Chief DiFronzo told News 12.

DiFronzo said the levels were as high as 265 parts per million on the second floor.

He said the building was being renovated.

Doors and windows were shut, which worsened the situation and that a gas-powered machine appeared to be the culprit.

Nassau County Chief Fire Marshal Michael Uttaro told News 12 that fire marshals “issued an appearance ticket to the contractor who was illegally using the gas powered equipment in the building, which caused the carbon monoxide emergency.”