When installing a gas heater in your home, other than choosing the type of gas you will be using, another choice you need to make is between a vented or vent-free model.  While there are pros and cons for each method, there are a few things to consider for vent-free models.

While most states allow the installation of vent-free heaters, there are a few that do not.  Some states also prohibit certain applications of vent-free heating, so check with your municipality before purchasing a vent-free unit.

The presence of other gas burning appliances may compete with the heating unit in using inside air for combustion.  Adequate fresh air needs to be integrated into the rooms, which can mean occasionally opening a door or window, or providing another method of ventilation.  Additional ventilation may also be required in homes with extremely tight construction.

Homes at higher altitudes may have pilot blowout or flame shutdown issues due to lower atmospheric pressure.  For bedroom or bathroom use, some states prohibit installation, while others allow smaller sized BTU units to be used.  Vent-free heating units may add moisture to the room.  In homes where the air is dry this can be helpful, while other homes may find condensate builds up on the windows.  Again, a little ventilation may be all you need.

Remember to have the heating unit installed by a qualified service technician.  Installing a gas heater is always best left to the professionals.