Fire officers have issued a warning after a smoke bomb left a family panicked in Hampshire.
Fire crews were called by a mother who thought she was trapped in her first floor flat with her two children by a large fire at 2315 BST on Wednesday.
Heavy smoke had set off their smoke alarm and filtered under the front door into the family's hallway and kitchen.
The device was set off inside the communal area of a block of flats in James Howell Court, Denmead.
The distressed family and their male neighbour were given advice over the telephone from the control room until three fire engines arrived.
Jennifer Dawson of Green Watch Control said: "The family were very panicky, I advised the occupants to go into the lounge and close the door, open the window and stay down low on the ground next to the window.
"I continued to reassure them until I heard the voices of the firefighters in the background of their flat."
It was 20 minutes before fire crews could give the all-clear.
Station Manager Bruce Gordon said: "I would like to remind people to think twice about taking part in something that may seem like a harmless prank.
"Although no harm may be intended it could put lives at risk if our resources are being unnecessarily sent to a bogus job."
The hoax happened within 24 hours of a serious house fire in nearby Waterlooville.