Abstract: At 7:00 p.m. on February 4, 2020, an employee and a coworker were performing maintenance on baghouse #4 and were assigned to weld on a coupler fitting in order to attach a device to measure the baghouse ventilation rates. The baghouse was an array of duct work that collected and removed particulates for commercial purposes. In order to access the elevated location where the device was intended to be installed, the workers were using a Werner D6212-1 12-foot fiberglass D-rung straight ladder. The workers positioned the ladder, and it was set up at approximately a 19-degree pitch which is 6 degrees out of the required inclination. The employee climbed the ladder and was welding the coupler on when he couldn't reach the top of it, so he extended his arm out and the ladder slipped and fell. The employee did not know that the ladder needed to be secured if it was not at the proper inclination and it was not possible to have the coworker hold the ladder because access to the bottom 4 feet of the ladder was restricted due to a nearby auger housing. The employee fell approximately 6 feet resulting in a proximal left tibia fracture, a comminuted left wrist fracture, a knee contusion, and impression acute tib-fib fractures with large knee joint. The employee was hospitalized for treatment.