Abstract: Employee #1 and other employees were to replace a 2 inch copper line from the CDA compressor to an air holding tank. The air line separated at a soldered junction injuring Employee #1 and four other employees. The air line separated because there was no full penetration of solder. The air line failed when the system was pressurized and a leak was detected at a union near the soldered section. Upon tightening the union, the air line separated injuring Employee #1 and the other employees. The air line was examined and it was concluded that it was not possible to see that full penetration of solder did not take place. Employee #1 sustained a fractured arm and was hospitalized.