All ventless gas products including Monessen are designed be used an average of 4 to 5 hours a day. Keep in mind the high BTU'S and how quickly the ventless gas logs or fireplace will heat the area. The efficiency doesn't get any better and that means that you are utilizing nearly 100 percent of the gas burned as heat. For that reason you wouldn't have the ventless gas log set or fireplace on for any length of time and need to shut it off periodically. So as you can see, the 4 to 5 hour window is quite generous and in most cases moisture will not be an issue. There are many variables that factor in the length of time a ventless gas log set or fireplace can be used. Here are some examples:

• What is the age of the home 
• How well insulated is the home
• How large is the area you are planning to heat
• Do you have energy efficient windows