The majority of modern furnaces, no matter how they are powered in your home, were designed to be especially safe during high usage periods. Thanks to updated furnace technology and built-in features, all heating systems are safe to run regularly. When it comes to electric versus gas, both were crafted with safety in mind. There are some factors that play into their levels of safety, however.
An electric furnace does not burn any fuel, so it will not have the same problems as a gas-powered furnace. The risks that stem from using an electric furnace include short circuiting and electrical fires. Thankfully, with the help of a professional, a proper installation and regular maintenance routine can effectively reduce the risk of either one ever happening.
As for a gas furnace, the largest threat a home or business owner will face is carbon monoxide, which can be quite deadly in heavy doses. It is quite rare for a furnace to release carbon monoxide into the air or for a leak to occur, though. Just like with an electric furnace, maintenance and proper installation methods will prevent any such issues.