There are three major ways that ventless logs affect the air quality inside your home: 1. They draw oxygen from within the room for the combustion process. If your home has adequate ventilation, chances are good you won’t notice an oxygen deficit while your gas stove is on. In a closed room, though, the supply of oxygen may fall below an acceptable level when your stove has been running for a time. This can cause headaches and breathing difficulties. This happens often enough that some manufacturers suggest you open a window while your fireplace is running. So two points here: if a window is open, your fireplace is no longer vent-free. If the weather is wintry, opening a window lets out the heat that you are trying to keep inside. What’s more, to be certified by the American National Standards Institute, ventless heaters must have oxygen deficit sensors, also known as ODS. These sensors shut off the heater if the oxygen level in the room drops below 18.5 percent. The normal level is 21 percent. 2. They emit any carbon monoxide left over from combustion back into the room. Carbon monoxide is a by-product of the combustion process in fireplaces and internal combustion engines. If it builds up to a toxic level – 1 percent or above – in your home, it can kill family members and pets in minutes. CO is impossible to see or smell. If you are asleep or otherwise incapacitated, you won’t even know about it before it’s too late. Otherwise, the following symptoms may alert you that CO has built up to a dangerous level: ●      Headache ●      Dizziness ●      Vomiting ●      Chest pain ●      Confusion Manufacturers suggest that owners of vent-free single or dual fuel fireplaces set up CO monitors as well. These devices sound an alarm if they detect levels are high. Many states and local codes already mandate CO detectors in residences. 3. Ventless gas logs also emit moisture into the room. A ventless gas log set cannot expel emissions up the chimney. It cannot get rid of the moisture leftover after combustion, either, except by releasing it into the room. Inside a gas fireplace, fuel and oxygen ignite. The fire consumes the gas, creating water and carbon dioxide waste in the process. One molecule of gas burned in combination with five molecules of O2 yields three molecules of CO2 and four molecules of H20. When a vented appliance exhausts CO, smoke and particulates to the outdoors, the moisture goes too. When a non-vented gas fireplace blows heated air into a room, that air contains all the moisture from the combustion process. Excess moisture can cause damage and mold or mildew growth. In a warm room, the moisture from ventless gas fireplaces condenses on the walls and ceilings. It potentially damages paint, wallpaper and wood furniture. Correct Sizing is Essential A ventless gas fireplace does not have a chimney. It must be the right size for the room. If the gas log set is too small, it won’t provide enough heat. If the unit is too large, it will use more oxygen and emit more toxins than necessary. To be as safe as possible, a vent free stove should have a BTU rating that fits the square footage of its location. In general, an output of 15,000 BTU or above is appropriate for a large space such as a great room. A vent-free heater that produces 5,000 BTUs or less is safer for small areas like a dining room or home office. For example, a dual fuel ventless gas insert from Duluth Forge produces up to 26,000 BTUs. It is sized for spaces up to 1,350 square feet. In contrast, the 15,000 model from Duluth Forge heats up to 600 square feet. Regular Maintenance for Safety Regular maintenance is part of owning a gas-burning, ventless appliance. It requires a thorough interior cleaning every three months. This includes keeping the air and fuel injector holes free of dust and particulates. If these holes are fully or partially blocked, it affects the unit’s efficiency. The combustion process will be incomplete, resulting in soot buildup. Incomplete combustion can also increase deadly carbon monoxide emissions. Regulations for Ventless Gas Logs Two out of fifty states, California and Massachusetts prohibit or strictly limit the installation of vent-free gas heaters due to safety concerns. Also, federal regulations ban installation of ventless gas-burning heaters in all HUD housing. Some large cities in states such as Texas and New York prohibit ventless gas heaters. In other states, local jurisdictions require certification from professional installers before permitting these appliances. Pros of Owning a Vent Free Heater ●      No need for a chimney or vent ●      Clean burning/energy efficient ●      Can go on interior as well as exterior walls ●      Governed by laws, safety guidelines, certifications and building codes Cons of Owning a Vent Free Heater ●      Consumes oxygen ●      Emits CO ●      Adds moisture to the air ●      Questions about safety Better Options in Ventless Heating If the data on ventless gas fireplaces concern you, find out about similar yet safer options in heating for your home. These include a vented log set or a non-combustion fireplace. If your home already has a wood fireplace with a chimney, you can put in a vented gas or wood-burning insert. You won’t have to go to the expense of having a venting system installed. Vented gas fireplaces provide the ambiance of a real fyre, just like a ventless heater. However, most of the toxic emissions go up the chimney, not into your living space. You can eliminate fossil fuel consumption, toxic emissions and the need for a chimney with an electric fireplace. This solution is the most popular alternative to a natural gas log set for builders and homeowners alike. Electric fireplaces don’t require a chimney because no combustion takes place. That means they don’t consume your oxygen or pollute your air. They don’t pose health risks like an unvented gas fire. The best electric fireplace brands have realistic flames and sound effects. For example, MagikFlame uses HoloFlame technology to produce a three-dimensional, realistic flame. Each model offers a choice of 30 fire styles.