Locals claim members of the public will be tempted to risk their own lives to tackle blazes.
It comes as Highlands and Islands Fire Board prepares to consider a plan to disband the local community units in Knoydart and on Eigg which the fire chief says would cost more than £400,000 to retain.
He says Knoydart has only three firefighters and has had only three emergency calls in the previous five years while the four-strong Eigg team had only one. He says both teams are struggling to attract recruits.
However, residents say there was a house fire on Knoydart some years ago, and members of the unit did manage to put it out before the Mallaig team arrived and crucially stopped other members of the community who wanted to become involved.
Grant Holroyd, second in command at Knoydart, said: "We are not trained or equipped to the highest level and accept it doesn't make sense to spend the money doing so.
"But what we think does make sense is to leave a team here which in the event of a fire can establish a water supply, get pumps set up, manage the public, stop people going into the buildings and if we can get water on to the fire safely, do so. They should be training us to do what is required without going into a burning building."
Stewart Edgar, chief fire officer of Highlands and Islands Fire Service, said £210,000 would have to be invested in each unit they were to continue and revenue costs for the previous five years were around £10,000 in both.
Mr Edgar, in a report to the fire board, says that in his professional opinion due to the inability of Knoydart and Eigg "to meet the board's agreed sustainability criteria, combined with very low levels of activity and risk", they should be deemed unsustainable and that emergency cover would continue to be provided by ferry from Mallaig.
Local people doubted fire service estimates the Mallaig-based team could get to a fire in Knoydart in 50 minutes and one in Eigg in 90 minutes.
Mr Holroyd added: "Other information they are working on is inaccurate. The population they say is 90 whereas it is more like 120. They suggest there are only about 20 bed spaces for overnight visitors, but on occasions there would be 200 here."
Maggie Fyffe, secretary of the Isle of Eigg Heritage Trust which owns the island, added: "There is still definitely a role for the fire unit to play here. The problem is that without a presence the local people will act themselves.
"It could be hours before the Mallaig team get over, by which time it is too late."