In an effort to determine the effectiveness of multiple types of fire sensors for early and reliable mine fire detection, the National Institute for Occupational Safety and Health (NIOSH), has evaluated multiple sensors for early mine fire detection and nuisance signal discrimination. Optical and ionization smoke sensors, carbon monoxide sensors, and metal oxide semiconductor (MOS) sensors were used to collectively differentiate fire products-of-combustion (POC) signatures from nuisance emissions produced by diesel equipment, metal flame cutting, and the charging of battery-operated mine equipment. Experimental results showed the clear advantage of smoke sensors over carbon monoxide sensors for early mine fire detection. NIOSH recommends that multiple types of fire sensors, such as smoke, carbon monoxide, and MOS sensors, should be implemented whenever possible to reduce the risk of nuisance fire alarms and provide early mine fire warning capability based on the expected fire and nuisance emissions sources. A rule-based system derived from the expected sensor responses could be implemented into a mine atmospheric warning system. To enhance miner safety, a smoke sensor should be used in a conveyor belt entry for early fire detection and at a battery-charging station to eliminate false chemical cell carbon monoxide alarms. With the operation of diesel equipment in underground mines, a NOx-sensitive MOS sensor can be used to discriminate diesel emissions and provide a positive indication of a fire. A combination of a carbon monoxide sensor, smoke sensor, and MOS NOx-sensitive sensor is one possible sensor combination for early mine fire detection and nuisance signal discrimination.