False alarms triggered by automatic heat and smoke detectors are costing nearly £500,000 a year, Cornwall Fire and Rescue Service has said.
The brigade said it responded to nearly 1,000 call outs in 2009 prompted by alarms going off because of cooking fumes or fire doors being wedged open.
Automatic detectors at a students' hall of residence in Falmouth went off 35 times in two years.
Each false alarm call out costs the service up to £500.
The service has been campaigning to cut the number of false alarms, which it said accounted for one-in-three call outs.
Falmouth watch manager Justin Ashburn told BBC News: "Logistically it can be a problem because it could be potentially taking us away from a genuine incident.
"However, when the call comes in, we do have to treat it as an emergency."
He said the costs incurred include the appliances, fuel, supervisory officers and security.
"In these austere times, we as a public service have to provide value for money for the tax payer as well as safety," Mr Ashburn added.