can this be used outdoors?

It is not weatherproof so you can't use it to heat an open space outside, you need some kind of shelter to protect the heater at the minimum. The heating elements can be very fragile as well so you don't want a lot of wind or vibration to reach the heater. It works best in a small workshop or room. I use one to provide heat for my dogs and another in a tortoise enclosure, both are indoors but unheated otherwise.