Cooking fires are among the most common types of house fires, causing around 48 percent of all residential fires. They are often caused by greases that become overheated on a stove or in an oven. (About 600 degrees Fahrenheit, on average.) When it reaches that point, it's usually too late. Thoroughly clean your cookware to prevent grease from building up over time. Portable cooking appliances, such as toasters and electric griddles can also be a source of fires. Never leave these portable appliances unsupervised, and make sure they are cool to the touch when storing them away. Toasters should be regularly cleaned of crumbs that might ignite if they build up inside the appliance. During the outdoor cooking season, barbecue grills left unattended on a wooden deck or near the exterior walls of a home can also be a source of fire. A heated grill next to a wooden fence can easily cause fire, and grills have been known to ignite the exterior walls of a home or garage if positioned too close.