Question: How long can a sandwich sit out before it becomes unsafe to eat?
Answer: Most types of sandwiches can be safely left out at room temperature for about two hours — or one hour if the temperature is above 90 degrees Fahrenheit. But it depends on the type of sandwich.
The two-hour timeframe (or one hour, if above 90 degrees Fahrenheit) applies to sandwiches made with deli meats (such as turkey, ham, chicken, bologna and roast beef); sandwiches made with other cooked foods, including egg salad, chicken salad and tuna sandwiches; and sandwiches made with cut vegetables like lettuce and sliced tomatoes.
The United States Department of Agriculture notes that it’s dangerous to eat cold cuts, sliced deli meats, cooked foods and cut vegetables that have been allowed to sit out at room temperature for two hours or longer (or 1 hour above 90° F). The reason is that bacteria grow rapidly when these foods are kept at temperatures between 40° F and 140° F. If sandwiches containing these ingredients have been left out of the fridge for longer than this timeframe, they should be discarded.
If you’re packing a sandwich that contains any of these perishable ingredients and you don’t expect to be eating it within two hours of leaving home (and you won't have access to a refrigerator within that same timeframe), be sure to pack ice or a frozen gel pack along with the sandwich to keep it colder and safer longer.
Sandwiches made with shelf-stable ingredients only, such as peanut butter, jam, jelly and hard cheeses (like cheddar) can be left out much longer. Since they contain no perishable ingredients, the amount of time you can leave them out is more a matter of quality than safety; these sandwiches will usually keep well for about a day when stored at room temperature.