At 17:18 hers Frederick ECC sounded tones for structure 11-30 for unknown odor in a structure on River Run Rd. D2, E111, E23, A248, C11-1, all responded. While en-route Frederick ECC advised responding units that their were multiple patients and was dispatching an EMS Task Force. D2 arrived on scene and established command, E111 arrived on scene and began investigating. E23 arrived on scene and took position at the hydrant and it's crew assisted E111 crew with investigating. A248 arrived on scene and reported to command. Command then advised ECC that their was about 30 adults and children that were in the building. A248, C11-1 and Medic2 were assigned EMS division. T41 and E31 arrived on scene and reported to command for assignment. The investigation crews could not find any signs off CO or any other gases and they still had a strong odor in the building. Command then requested hazmat crew to be dispatched to the scene to assist with finding what was causing the odor. A247,A249, A18, A19, A28, A38, A39, all were on scene to assist with EMS care to 30 adults and children. A248 and A38 both had patients that needed to be transported to FMH for further evaluation. Special Ops 50 and Decon 33 and Special Ops33 arrived on scene to assist with finding the cause. After several hours it was determined that one of the adults had thrown away a pepper spray aerosol can that had busted away in a trash can which was the cause of the unknown odor. Units then went in service when ready.