A "fireplace humidifier" typically refers to one of two main types of products designed to add moisture to dry indoor air, often during winter when fireplaces or wood stoves are in use:
Decorative Flame Humidifiers: These are modern, electric ultrasonic devices that simulate a cozy fireplace flame effect while releasing a cool mist to humidify the air. They're popular for bedrooms, offices, or living rooms as night lights, aromatherapy diffusers, or ambiance enhancers. They don't produce actual heat or fire—just a visual illusion using LED lights and mist refraction.
Cast Iron Steamers for Real Fireplaces/Wood Stoves: Traditional, non-electric pots or kettles made of cast iron that sit on top of a wood-burning stove or fireplace insert. They heat up with the fire, evaporating water into steam to humidify the room.