What is a Firebox? Fireboxes come in various sizes and capacities. Essentially, the firebox is where the fire is situated and allows a range of multi-fuels to be used, including natural gas. In the majority of cases, the firebox is installed into the chimney breast (or specially constructed recess with ventilation) and then a selection of attractive fire surrounds can be installed in front of the fire box. This combination then provides both highly efficient heating and a stunning fireplace that complements and enhances the room. Fireboxes can also be used on their own, without a fireplace surround and the fire is enjoyed through the front window elevation. This section shows the different types of fireboxes that are available and the resulting heating options that can be specified.