No, you should never leave a fireplace burning overnight or unattended during the day. While fireplaces are made to contain fires, fires can and do spread from fireplaces, so it’s crucial that you’re there to monitor them and put them out if needed. If you’re worried about putting out a fire before bed, stop feeding it fuel long before bedtime and actively put out the fire using your poker, a shovel, and some baking soda.

Most installations take 1-3 days, depending on system complexity and building size.

Baking soda is an effective fire reduction method. However, flour and baking powder are very dangerous around flames. Flour is flammable and it can also conduct electricity. The combination can cause serious injury from electrical shock and worsen the situation by adding fuel to the fire. Baking powder is also not an option as it's also highly flammable. 

A fireplace hearth is necessary in most areas per building codes, especially for gas and wood-burning fireplaces. Electric fireplaces may not require a hearth, so check local building codes or ask a pro for guidance if you’re leaning toward electric. A fireplace hearth can decrease the risk of flying embers creating a fire and burning your home down. That’s why fireproof material, like tile, is used for the hearth.