Don Vandervort, Head Homeboy, has written more than 30 DIY home improvement books, been a segment host on HGTV, served as MSN.com's home improvement expert and written countless magazine articles.
In some parts of the country, codes allow the use of vent-free fireplaces. Vent-free or "no-vent" fireplaces, made by several manufacturers, have an oxygen-depletion sensor to shut off the gas if the oxygen level ever drops below a preset level. In addition, their burners produce only very low levels of carbon monoxide.
Because all their heat is recirculated into the room, these have very high efficiency ratings. On the downside, they have a much smaller and less realistic fire than other fireplaces. Also, product directions usually require you to leave a window slightly open during use.
