When the employees of a restaurant attended a fire safety seminar they watched a fire official demonstrate the proper way to operate an extinguisher. ""Pull the pin like a hand grenade"" he explained ""then depress the trigger to release the foam."" Later an employee was selected to extinguish a controlled fire in the parking lot. In her nervousness she forgot to pull the pin. The instructor hinted ""Like a hand grenade remember?"" In a burst of confidence she pulled the pin -- and hurled the extinguisher at the blaze.