South Yorkshire Fire and Rescue Service has issued the alert following a number of incidents with calls made to residents in the few days offering to fit devices for free and claiming to be fitting them on behalf of the fire service.
A spokesman said: “We've been made aware of a company cold calling people in Doncaster saying they will fit smoke alarms for them for free and then charging monthly fee.
“They say they are fitting them on behalf of the fire service.
“They are not.
“We do not charge for smoke alarms and we do not use businesses to carry out this service on our behalf.”
Residents can request free smoke alarms from the fire service as part of a free home safety check.
To see if you are eligible, visit the service’s website www.syfire.gov.uk