We tested two aerosol fire sprays, the First Alert Tundra and the Shield Fire Protection Kitchen Guard, and have judged each as Don't Buy: Performance Problem. Unlike the extinguishers we tested, neither has a pressure indicator that shows whether the unit is ready for use. And the sprays are not intended to replace a standard extinguisher (NFPA 10 compliant) where required, as the makers say on the labels. The sprays sometimes made the grease fire in our tests flare up before they put it out. That could cause the fire to spread or prompt the user to stop the spray. We found that two of the 10 Tundra samples didn't properly discharge.