ZigBee is like any other wireless technologies. Depending on country regulations, ZigBee can support distances of up to 30 meters in an open environment with a 100mW antenna. Some sensor-based products that are battery operated may not be using 100mW and therefore, could be much less than 30 meters. It is recommended to test out the RF range in a real environment for any deployment with any market-available ZigBee Range tester such as from Telegesis.