As their name suggests, decorative fireplaces aren't designed to produce heat; some may have a reasonable heat output, but they are mostly designed to provide the look of a fireplace and wood fire. Their function is primarily aesthetic and can be grouped into three types, according to the fuel they use: electricity, gel and gas fireplaces.
The use of gas and gel decorative fireplaces is very questionable. There are other means of creating ambiance without emissions and the risk of fire; only electric decorative fireplaces - with both heating capability and only-flame effect - are safe.
Decorative electric fireplaces
If you do want a decorative fireplace, consider an electric unit. They are clean, relatively cheap, safe and easy to install.
And they may have a realistic flame, and also some heat output.
For customer reviews and prices on Amazon.com, see: Electric fireplaces
gas log fireplaces
Decorative gas log fireplaces use either natural gas or propane and may come with or without an enclosure.
Enclosed freestanding fireplaces should be properly vented.
Manufacturers claim that gas log fireplaces designed to be installed in existing fireplaces and using existing chimneys produce very few pollutants and have very limited risks. But they are rather useless, and many jurisdictions have specific requirements for them. Prices vary mostly in the range of $100 to $300.
Decorative gel fireplaces are fueled by an ethanol- or alcohol-based gel. They are typically ventless units.
Some of these fireplaces comprise a set of logs (5, 6, 7...) and some cans of gel-fuel. They do not involve formal installation (they just have to be assembled) and are mainly used in dormant fireplaces.
Gel fireplaces are relatively cheap ($100-$150) and produce negligible quantities of smoke, smell or fumes, which may explain their many favorable customer reviews. But each gel costs about $3 (2-3 hours burn time) and the fuel is highly flammable; and they have a negative impact on the indoor air through the quantities of water and CO produced during the burning. These effects are particularly hazardous to asthmatics and allergy sufferers…