There are two main types of flame detectors: infrared (IR) flame detectors and ultraviolet (UV) flame detectors. IR flame detectors use photoelectric cells that are sensitive to infrared radiation emitted by flames to detect fires. They work best for open storage areas and can detect fires within 90 meters. UV flame detectors detect the ultraviolet radiation emitted by flames and can be made insensitive to sunlight to prevent false alarms.