Firefighters battling a deadly factory fire in Melbourne's southeast were put at additional risk because of a malfunctioning pumper, the union claims.
A factory worker was killed when the blaze took hold of the Superior Drive business in Dandenong South on December 8.
Four others, including two firefighters, were injured.
The United Firefighters Union says an ultra-large pumper malfunctioned during the incident, only producing half a tank of foam and emitting toxic black smoke.
Victorian branch secretary Peter Marshall said the firefighters had no choice but to work alongside the toxic material for seven hours as they tackled the blaze.
"Firefighting appliances such as this ultra-large pumper should be replaced after 15 years but this firefighting appliance is over 20 years old," he said in a statement.
A video of the scene shows black smoke coming out of the vehicle, with station officer Breanne Geyle describing how difficult it was to work in the conditions.
"The foam pump throttle has been reported several times," she says in the video.
"Nothing has been done about it yet and it's really causing a lot of impact to us in this working environment.
"It's also an extremely hot and windy day and having the truck with the black smoke is just another challenge that we unfortunately have to face, which is unnecessary."
A Fire Rescue Victoria spokeswoman confirmed one appliance experienced a mechanical issue but it was repaired by specialist mechanics that same afternoon.
"This did not impact the firefighting effort," the statement to AAP said.
"Crews are to be commended for their outstanding efforts, which prevented further loss of life and property."
But Mr Marshall said fire crews were also without Dandenong's critical ladder platform because it was sent to Traralgon to cover the breakdown of another ladder platform.
The unavailability of critical appliances only highlighted the need to upgrade Victoria's firefighting fleet, he said.
"Fire Rescue Victoria's policy is that vehicles are to be replaced at a maximum age of 15 years," Mr Marshall said.
"But over 70 fire trucks are so old that they should be immediately off the road, including one truck over 36 years old.
"These outdated trucks are putting the lives of professional firefighters and the community they protect at risk."
