Can a close nipple be used in a gas line?

Yes, a close nipple can be used in a gas line, provided it meets the appropriate material and sizing standards for gas applications. It is crucial to ensure that the nipple is made of suitable materials, such as black iron or steel, and that it is installed according to local codes and regulations. Proper sealing and connections are also essential to prevent leaks and ensure safety. Always consult with a qualified professional or local building codes before installation.