Dapto and Warrawong fire stations are under threat of temporary closure as the service responds to pressure to cut costs, the firefighters' union says.
From next week, the 24-hour stations could close any time a firefighter went off sick, the Fire Brigade Employees Union said.
Dapto station commander Darin Sullivan said the cost cutting was dangerous and a threat to public safety.
"Usually if someone goes on sick leave we have a spare [firefighter] in the system to fill that hole. Once they are used we would recall an off-duty firefighter," Mr Sullivan said.
"As of next week, the fire brigade is going to start not filling that vacancy, meaning that truck is not able to respond."
The directive meant Dapto and Warrawong stations were "under threat of being off-line for the first time".
"It's a dangerous situation. There are meetings across the state today and already they're starting to roll it out," Mr Sullivan said.
Both stations have one fire truck, an officer and three firefighters 24 hours, seven days a week.
"Now for the first time they will be going off-line to suit the fire brigade budget."
Mr Sullivan said the move was in response to the NSW Government's directive to all public services "that they need to cut 1.2 per cent off operational costs".
Fire & Rescue NSW (FRNSW) said yesterday it was considering taking stations "off-line" to save money but denied any decision had been made.
"A further strategy being discussed is where there is a vacancy, and a full crew is unavailable, certain fire trucks may be temporarily taken off-line," a spokesman said.
"No decision has been made on whether this strategy will be adopted, nor have any fire stations been identified."
The service was trying to maximise the attendance of firefighters at work, "thereby minimising absenteeism".