Commercial kitchens are found in restaurants, cafeterias, hotels, hospitals, educational and workplace facilities, army barracks, and similar establishments. These kitchens are generally larger and equipped with bigger and more heavy-duty equipment than a residential kitchen. For example, a large restaurant may have a huge walk-in refrigerator and a large commercial dishwasher machine. Commercial kitchens are generally (in developed countries) subject to public health laws. They are inspected periodically by public-health officials, and forced to close if they do not meet hygienic requirements mandated by law. The evolution of the kitchen is linked to the invention of the cooking range or stove and the development of water infrastructure capable of supplying running water to private homes. Food was cooked over an open fire. Technical advances in heating food in the 18th and 19th centuries changed the architecture of the kitchen. Before the advent of modern pipes, water was brought from an outdoor source such as wells, pumps or springs.