This furnace fan is powered by transforming heat into energy, without using any battery or electricity, energy conservation and environment protections. Easy to use, just put it on the burning furnace, it will automatically absorb thermal energy and drive fan produce wind. Thus it can circulate heat throughtout theroom, increase air circulate speed and promote the furnace's heating efficiency. The fan's rotation speed is depends on the temperature of stove, the temperature is higher and the rotation speed is faster. There are 8 colors for you to choose, you can choose according to your demands. Features: This furnace fan is powered by transforming heat into energy, without using any battery or electricity, energy conservation and environment protections. There is a thermoelectric module on the fan as a small generator to drive the motor of fan. Easy to use, just put it on the burning furnace, it will automatically absorb thermal energy and drive fan produce wind. The fan outputs 180-210 CFM to help spread warm air throughout the room, increase air circulate speed and promote the furnace's heating efficiency. The fan's rotation speed is depends on the temperature of furnace, the temperature is higher and the rotation speed is faster. This furnace fan is silent and quiet, and the noise is lower than 25dB. The ranges of working temperature is about: 140-662 / 60-350. Note: the temperature can not be over 662F when using the furnace fan. Specifications: Name: Fireplace Fan Model: YL505 Material: alumina Color: black, gold, silver, grey, bronze, red, rose red, blue (optional) Blade number: 4 CFM: 180-210 Speed: 1100rpm Noise: 25dB Working Temprature: 140-662 / 60-350 Item size: 135 * 108 * 223mm / 5.31 * 4.25 * 8.78in Item weight: 630g / 1.39lb Package size: 186 * 139 * 218mm / 7.32 * 5.47 * 8.58in Package weight: 860g / 1.90lb Packing List: 1 * 4-Blades Fireplace Fan