The Fire Brigade Employees' Union (FBEU) is concerned Picton, Warragamba and Camden Fire and Rescue NSW stations could face temporary closures.
The union says Fire and Rescue NSW (FRNSW) has been trying to implement an order which would allow these stations to be "temporarily taken off-line in the event of a staffing shortage".
However, FRNSW says the needs of the community will always be taken in account when making any decision to take an appliance offline.
FBEU state secretary Martin Dixon said the union was fighting the proposal in the Industrial Relations Commission.
"The population of NSW is growing by over 100,000 people every single year. That means more people, more houses, and more vehicles on the roads," he said.
"The NSW Government should be turning its mind to increasing fire services to serve this increasing population, but instead, they want to shut local fire stations down to save money.
"At the moment, fire stations without sufficient safe crewing levels are supplemented by other firefighters at overtime rates, which is necessary to keep our communities safe. Staffing shortages can be avoided by fixing the critical understaffing and underfunding of the service."
FRNSW Deputy Commissioner, Jeremy Fewtrell said the organisation was committed to keeping communities safe and uses a 'risk-based approach' to manage its emergency service delivery.
"FRNSW has an established procedure of managing all of its on-call fire stations, and the practice of taking fire trucks temporarily off-line is partly a result of changing demographics, improvements in technology, and a more modern understanding of fire safety and risks," he said.
"Under FRNSW's risk-based approach, which was formalised in conjunction with the FBEU in 2008, a fire truck is only temporarily taken offline when there are more than sufficient resources in the area to respond to emergencies. These decisions are based on data including ongoing incident response coverage of the area by other nearby appliances.
"Each fire truck and its crew is a mobile resource available to respond wherever it is needed. FRNSW's network of coverage is managed centrally from Communication Centres and is able to provide rapid emergency response based on the fastest available resource, independent of a fixed fire station locations.
"The needs of the community are always taken into account when making a decision to take an appliance offline."
However, FRNSW would not address if Camden, Picton and Warragamba stations would be shut in the event of staffing shortage when asked by the Advertiser.
Mr Dixon said the union would fight this proposal through the courts but called on the community for additional support.
"We encourage people to write to their local State Member of Parliament, write to the Minister for Police and Emergency Services, write to the Commissioner of Fire & Rescue NSW and make your voices heard," he said.
"We want people to let their family and friends know that this government wants to shut down their local fire station, depriving them and their community of a critical emergency response if anything goes wrong.
"And most importantly, we need the community to support our local firefighters, who are of course at the centre of this proposal.
"They are doing their best to maintain this vital service, and their employer wants to throw them aside and allow their local community to be exposed."