The fireplace has frequently been the location where toddlers acquire significant injuries including lifelong scars. So, it is appropriate to assess your fireplace and perhaps make some modifications.
The hazards around the fireplace are not limited to burns from an active fire. Toddlers frequently "bonk" on the raised hearth edge, gain access to hot ashes and pinch fingers in folding doors. Access to the fireplace tools, grate, wood and gas key are also reasons for concern.
The comprehensive solution to all of these issues is to encircle the entire hearth and fireplace with a gate. The best product for doing so is the HearthGate by KidCo. This is a great solution if your hearth has a raised edge and if you occasionally have fires. The HearthGate is also the best solution to protect freestanding wood stoves.
If your hearth does not have a raised edge, you can focus on preventing access to the fire box. Glass doors can be readily latched closed to prevent access to the fire box, grate and ashes. Fireplace tools and the gas key should be relocated out of the area when not in use.
If your hearth has a raised edge, you may want to cushion it. Traditionally, stick-on cushions were used to do so, but these were frequently rendered ineffective when curious toddlers peeled them off. A slight improvement on this approach consists of the cushion mounted on a metal frame which is then pressure fit on the hearth. The best and most attractive solution is a custom made cushion which covers not only the edge, but the surface as well. These upholstered cushions effectively create an additional padded seating area while eliminating the hazard of the hearth edge.
Finally, a free-standing fireplace screen is not an effective barrier to a curious toddler. Alternatives include replacing the screen with fixed tempered glass doors or securing the screen in place. We elected to secure our screen to the damper with a bungee cord and use candles rather than wood in our fireplace.
You can see that the extent to which action is necessary depends upon multiple factors including the whether your hearth is raised or flush, whether you have doors or a screen and whether you wish to have fires or not.