Proper storage, sanitary tools and work spaces, heating and cooling properly and to adequate temperatures, and avoiding contact with other uncooked foods can greatly reduce the chances of contamination. Tightly sealed water and air proof containers are good measures to limit the chances of both physical and biological contamination during storage. Using clean, sanitary surfaces and tools, free of debris, chemicals, standing liquids, and other food types (different than the kind currently being prepared, i.e. mixing vegetables/meats or beef/poultry) can help reduce the chance of all forms of contamination. However, even if all precautions have been taken and the food has been safely prepared and stored, bacteria can still form over time during storage. Food should be consumed within one to seven (1-7) days while it has been stored in a cold environment, or one to twelve (1-12) months if it was in a frozen environment (if it was frozen immediately after preparation). The length of time before a food becomes unsafe to eat depends on the type of food it is, the surrounding environment, and the method with which it is kept out of the danger zone.