BREATHING masks worn by NSW firefighters are endangering lives with the vital gear failing during fire rescues.

A warning has been issued across the state for the new MSA AirGo sets to only be used for 10 minutes while firefighters battle blazes.

Fire and Rescue issued a new safety edict on the breathing apparatus after firefighters reported the masks were faulty and "freezing up", potentially putting their lives and others at risk.

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The defective sets, bought by the State Government for more than $5.5 million in 2016, are locking up in the "open position", allowing air to flow continuously out of the mask.

"The uncontrolled flow will rapidly deplete air supply, representing a safety risk to firefighters in hazardous atmospheres," the bulletin stated.

All fire trucks in the Greater Sydney Area, Wollongong and Newcastle were ordered to replace the faulty masks with the old ones. - the Drager SCBA

But The Sunday Telegraph can reveal each truck - which carries four of the new masks - were given just two of the older ones.

With firefighters only able to spend 10 minutes inside a blaze wearing the AirGo masks, more trucks and fireys must now respond to emergencies.

The Sunday Telegraph understands a massive fire at Sylvania Marina on Tuesday night - just hours after the new mask warning was released - was the first time extra resources had to be sent.

"Breathing apparatus is the most important piece of equipment on a fire truck," one senior Sydney Station Officer told The Sunday Telegraph.

"It is the only thing that allows firefighters to breathe in smoke and toxic atmospheres and the only thing that allows us to save the lives of people trapped.

"It says a lot about the Commissioner - who was brought in from New Zealand by the government two years ago - and his incompetent senior management team that they can't even get this basic stuff right," he said.

Fire and Rescue said it was working the supplier of the masks to "address the issue as a matter of priority".

"Fire and Rescue NSW have acted swiftly to ensure the health and safety of all of their officers," Acting Emergency Services Minister, Mark Speakman, said.

"They are working to identify any potential issues with the equipment and will assess possible solutions if required. The agency remains ready to respond to any potential incidents."