Abstract: On February 22, 2011, Employees #1, #2, #3, and #4 were working in a shop area that contained a running forklift. The shop had two large roll top doors, one at the west end and one at the east end of the building, which remained closed due to outside temperatures consisting of about 30 degrees Fahrenheit. Also, the shop area measured 55 feet by 100 feet and had a 20 foot peak height. After their workshift ended, at approximately 7:00 p.m., Employees #1, #2, #3, and #4 began experiencing headaches. All four employees were taken to a nearby medical facility, where they underwent evaluation and blood tests. The results indicated that Employees #1, #2, #3, and #4 received overexposure to carbon monoxide; they were hospitalized and treated. The accident investigation revealed that the forklift had been running for approximately two hours during the employees' workshift at a level greater than 1,000 pm.