Our Sparkler Machines feature Cold Spark Technology (CST) and are capable of producing a spectacular vertical fountain of golden sparks from 7 feet to up to 17 feet high, and they are safe to the touch and cool as soon as the sparks hit the air. These units are designed to be used indoors but can also be used outdoors with weather permitting. They easily can be wired to up to 10 units at once firing off simultaneously to WOW your audience. Make sure if you rent these to use Sparktacular Brand as they are Fire Marshall approved in most states and have safety features that other units do not have.