Cold rooms are most commonly used in the catering industry to keep food chilled without having to use refrigerator units. In essence they are walk-in refrigerators that can be built to order by several companies. Cold rooms are insulated rooms that are used for the temporary storage of perishable items such as food, flowers and livestock as well as frozen goods and do not have ventilation. The lack of ventilation makes the storage of certain gases and chemicals ill-advisable due to the potential for evaporation and the creation of explosive atmospheres. There is also a risk of mould developing in cold rooms and spreading quickly to cover not only surfaces but also to contaminate the items being stored in the cold room. There are at least five different categories that cold rooms can be divided into: 1) Medium temperature cold rooms that are used for fruit and vegetable storage where the temperature is always above 0 degrees. 2) Low temperature cold rooms that are used for the storage of meat and have a temperature below 0 degrees. 3) Stand-alone cold rooms that are equipped with on board compressor-condensers that are used by hotels and restaurants. 4) Cold rooms with remote condenser or packaged units that are used in small food stores, smaller hotels and restaurants. 5) Centralised cold rooms that do not have on board compressors but have remote compressor racks. These are mostly used by supermarkets and distribution centres. The demand for cold rooms is so great in the catering industry that you can now purchase and hire mobile cold rooms.