What color bulb is required for a head in a heater zone within a 7 ft circle?

In sprinkler systems, especially in the context of a heater zone, color-coded bulbs are used to indicate specific zones and conditions. The blue bulb is designated for areas within a 7-foot radius around a head in a heating zone because it signifies that the sprinkler system is intended for use in environments where heat is generated, allowing the system to function adequately in conditions that may be influenced by heat sources.

This color designation helps ensure safety and efficiency by clearly marking areas that may require specific handling or precautions due to potential heat interference with the system's operation. Using blue in this context allows workers to quickly identify the proper operating zones, minimizing the risk of mistakes in management or maintenance of the sprinkler system.