When the power goes out, the clock starts ticking on everything in your fridge and freezer. Whether it's a severe storm, a fallen power line, or a grid emergency, the loss of electricity can put your food safety at risk. Experts say that a simple sniff test doesn't tell you everything you need to know. Two food safety specialists recently discussed how long food actually stays safe during an outage, what signs indicate it's time to throw something away, and what steps you can take to protect your perishable items. A refrigerator can keep food cold for about four hours if the door remains closed, according to Dr. Vanessa Coffman, alliance director for Stop Foodborne Illness. A full freezer can maintain a safe temperature for around 48 hours, or 24 hours if it's only half full, but only if the door is kept shut. Both experts emphasized that keeping the refrigerator and freezer doors closed is crucial. Every time you open the door, cold air escapes, causing the temperature inside to rise more quickly. Experts caution that you can't reliably tell if food is safe just by looking at it, smelling it, or tasting it. Food can contain harmful microorganisms without showing visible or odor signs of spoilage. Perishable foods like milk, cheese, meat, poultry, seafood, and leftovers should not be left at room temperature for more than two hours. If they've been at room temperature longer than that, they should be thrown away to avoid the risk of foodborne illness. After power is restored, check the temperatures in your refrigerator and freezer. If an appliance thermometer in the freezer reads 40 degrees Fahrenheit or below, the food may be refrozen. If you don't have a thermometer, check individual frozen packages. Food that still contains ice crystals or is 40 degrees Fahrenheit or below can generally be refrozen or cooked. If there's no thermometer, no ice crystals, and the temperature is above 40 degrees Fahrenheit, it's best to discard the food to avoid any risk. Keeping appliance thermometers in your fridge and freezer can help you monitor food safety. During an extended power outage, a rolling cooler can act as an "access cooler" for the items you use most. Move perishable items like milk, lunch meat, yogurt, and other refrigerated foods into a cooler with enough ice or frozen gel packs to keep them at 40 degrees Fahrenheit or below. Reusable ice packs can be placed in coolers alongside perishables or stored in the freezer year-round. Some devices can plug into an outlet and monitor your refrigerator, freezer, or other essential appliances, alerting you with a loud sound and flashing light if the power goes out.