As winter chills settle in, space heaters become a cozy go-to for warmth—but firefighters are sounding the alarm about a dangerously common mistake. Plugging a space heater into a power strip might seem harmless, but it can actually turn deadly. Fire departments across the country, including the Umatilla County Fire District in Oregon, are warning: never plug a space heater into a power strip or extension cord. These strips simply aren’t designed to handle the intense electrical load, and doing so could cause them to overheat or catch fire.

This warning isn’t just theoretical. In Ohio, a space heater connected to a power strip sparked a devastating house fire after igniting a nearby couch. Within minutes, flames engulfed the home. Space heaters can reach temperatures of up to 600°F—enough to turn a minor mistake into a major tragedy. Despite their convenience, these small appliances demand serious caution.

To stay warm safely, experts say you should always plug space heaters directly into a wall outlet. Keep a 3-foot safety zone around the unit, free from curtains, furniture, blankets, or anything else flammable. Never leave a heater running when you’re sleeping or not in the room, and always