An air purifier for a protective garment is connected to the protective garment with a air duct and has a housing having an inlet and an outlet, a filter attached to the inlet, a fan mounted in the housing adjacent to the filter, a thermal conductor mounted between the fan and the outlet, a thermoelectric cooling module attached to the thermal conductor and a power supply mounted in the housing and connected electrically to the fan and the thermoelectric cooling module. When the fan rotates, air outside the housing is filtered by the filter and drawn into the housing, appropriately warmed up or cooled down by the thermal conductor and flows into the protective garment. The air purifier provides clean air for a user wearing the protective garment at room temperature.