Abstract: At 3:40 p.m. on March 11, 2014, an employee was operating a converted (from G) propane powered industrial truck in a closed warehouse. The office space was 434 square feet with 9 foot ceilings, with an entry door on the south side of the building. The warehouse was 1,085 square feet with 14 foot ceilings, with a 434 square foot storage space above the office space. A combined warehouse/storage totaled approx. 17,360 cubic feet and the office was approximately 3,906 cubic feet. The office and warehouse had one interior door between them. The warehouse had one bay door and an emergency exit door to the north side of the building. The building had one flue at the radiant-heat, natural gas boiler, and the heater was located within four feet of the ceiling in the northwest corner. Carbon Monoxide (CO) measurements from the boiler, taken by the fire department and CSHO, ranged from 0 to 10 ppm following complete ventilation of the space and subsequent firing of the boiler. The building did not have any other ventilation system. The owner had owned the Towmotor industrial truck for approximately 40 years and it had 2,900 hours on the tachometer. The employee arrived at work at 8:33 a.m. according to video of the exterior of the building. The employee moved a van from the warehouse at 9:50 a.m., and closed the bay door. The space would not have allowed movement of the forktruck without removal of the van. A co-worker estimated the employee used the Towmotor for approximately one hour, between 9:50 a.m. and 11:50 a.m. Although the co-worker was gone from the building during some of this time. According to the video, the exterior doors remained closed during this time. Between 11:23 a.m. and 11:32 a.m. the Towmotor was off, and the employee was conscious and spoke to the co-worker and a carpet installer. The co-worker said the employee acted normal, and then the installer said the employee seemed to take a long time to convey his thoughts. At 11:50 a.m., the co-worker used the bathroom in the warehouse and did not see the employee. He said he thought the employee had gone home. Video of the exterior of the building confirms the employee did not leave the building. The co-worker said upon returning to the office he suddenly felt nauseated, warm and confused. He telephoned his wife for a ride, but left a message that he would either go to the emergency room or go home. He was 83, and said he recently recovered from bronchitis. He left in his own vehicle at 12:06 p.m. The co-worker said he looked in the warehouse prior to leaving and did not see the employee. He assumed the employee had left the building using the rear exit. The co-worker said he drove home, approximately 30 minutes, with the car windows open despite it being about 40 degrees F. He telephoned his doctor but gradually felt better over the afternoon and he did not see his doctor until March 14, 2014. A delivery driver opened the bay door at 2:49 p.m. and closed it at 3:15 p.m. The delivery driver then went to the bathroom where he found the employee collapsed on the floor. The emergency medical services (EMS) and fire department arrived at 3:28 p.m. and opened the bay door at 3:31 p.m. The EMS responders had a reading of 100 ppm CO inside the building when they removed the employee from the bathroom. The employee was dead from acute carbon monoxide intoxication.