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What is Vent Free? Is it safe?
Frequently-asked Questions about vent-free fireplaces.

What exactly does vent-free mean?

Vent-free, or ventfree, simply means that the gas heater or fireplace is not vented to the outside. Vented heaters bring in air from the outside, and then exhaust the combustion byproducts to the outside. Vent-free units burn inside air and do not require a vent.

If they aren’t vented, where does all the carbon monoxide and fumes go?

Vent-free heaters are safe to use without venting. You may already have other vent-free gas appliances in your home now, such as a gas range, oven, or dryer. They don’t need to be vented because LP gas (propane) and Natural Gas are very clean-burning. Yes, there are tiny, tiny amounts of carbon monoxide and other gases that are released into the air, but these amounts are very small and are regulated by the EPA. Procom and Kozy World units are tested by the CSA (formerly called the American Gas Association) and proven to operate within the safe limits established by the EPA.

Blue flame or Infrared?

Ventfree heaters come in two types - blue flame and infrared. All sorts of silly claims are made as to why one type is better, or more 'efficient', than the other, so here are the facts. Both are 99.9% efficient. Both use the same amount of gas and produce the same amount of total heat. Infrared heaters have ceramic plaques that glow orange when they are hot. Blueflame heaters have a horizontal steel bar with a blue flame coming out the entire length of the bar. A piece of smoked ceramic glass is mounted in front of the flame.

Infrared heaters will feel hotter if you stand directly in front of them, which is why some people believe they are more efficient. They are not more efficient, they simply direct the heat outward from the unit moreso than a blueflame unit does. The glowing orange plaques, like our sun, produce infrared rays. Infrared rays travel through the air and are absorbed by things they hit. If you are standing outside on a cool, cloudy day, and an opening in the clouds occurs, you will suddenly feel warmer. The air around you did not suddenly warm up, rather the infrared rays from the sun passed through the air and were absorbed by your skin, so your skin was warmed. If you mounted an infrared heater and a blueflame heater side by side, there would be a little more hot air rising from the blueflame heater, and the infrared heater would be projecting more heat out, away from the unit.

So how do you choose? If you want a heater that you can stand in front of, after coming inside from the cold, choose the infrared. It will feel more like standing in front of a fire. In all other cases, choose the blueflame. Blueflame heaters have two advantages. First, because they do not project the heat outward as much as infrared heaters do, you don't need to be as careful with furniture placement (infrared heaters can fade fabric and cause damage to furniture that is placed too close to the heater). Second, blueflame heaters typically have a range of heat output that is controlled by the thermostat. For example, a 30k btu blueflame heater will usually have an output range of around 15k to 30k. Infrared heaters, if equipped with a thermostat, are either on or off at their full rated output. (Manual control infrared units will have 2 or 3 heat output levels.)

What about carbon monoxide?

The amount of carbon monoxide produced by a vent-free heater is so small that a detector will not sound an alarm. And the normal “breathing” of your home, where outside air gets into your house through cracks, crevices, doors, windows, etc, means that the chemicals will not “build up” inside the house.

What are the Benefits of Vent-Free Heaters and Fireplaces?

  • Initial Cost - Ventfree heaters and fireplaces cost about one third the price of vented heaters and fireplaces.
  • Installation Cost - Vent-free heaters and fireplaces require no venting, so you don’t need a chimney, a hole in the wall, vent kits, termination kits, etc. All you need to do is run a gas line to the place you want to put your heater or fireplace. A plumber or heating/air-conditioning technician can do this for you.
  • Operating Cost - Vent-free heaters and fireplaces are 99.9% efficient. Compared to vented appliances that are typically 65-80% efficient, you are getting 25-50% more heat from the ventfree unit for the same price. Vented heaters must be vented through a wall, up a chimney, or through the ceiling and attic. This is costly, and once you’ve put it there, you can’t move it. To move a vent-free heater, all you do is disconnect the gas line, move the heater anywhere else in your home, and hook it up to another gas line.

Do Vent-free Heaters Produce Fumes?

If a unit produces any significant smoke or fumes, it is not operating correctly and should be checked out by a gas technician. Gas burns very cleanly and does not produce soot or film.

However, since it is burning the air inside your home, it is also burning whatever is in your air. If you have a smoker in the home, or you use lots of cleaning agents, air fresheners, or you have recently painted or stained, the burning of those particulates can create odors and/or film. In addition, when a gas appliance is used the very first time, there may be some fumes for a few hours until the oils and gunk from the factory are burned off, but after that, you shouldn’t smell it at all.

The “fume story” is something you might typically hear from someone in the hearth industry who sells $3000 to $4000 vented fireplaces. The vent-free industry has cut into their sales a lot, so they sometimes exaggerate or even make up stories to steer you away from the lower cost options you have.

Natural Gas or LP - What's the Difference?

If you live in a populated area, you may have gas lines that run underground and into your home. These lines bring natural gas to your home, and you receive a gas bill every month.

In less populated areas, it is not economical to run gas lines underground, so people use propane gas, also called LP (liquid propane). To use LP gas, you need to have a tank in your yard (or buried). The propane company comes to your house several times a year and fills up your tank. They run a line up to your house, and then a plumber or gas technician runs lines inside the house to the various gas appliances.

Heaters and fireplaces must be ordered in EITHER natural gas OR LP. Beginning in 2008, manufacturers started to come out with new models called "Dual Fuel" that can run on both natural gas and LP, without conversion. Dual Fuel appliances have TWO gas connections (one for Natural Gas, one for LP), two pressure regulators, and a special dual-fuel gas valve with a switch that you set to LP or Natural Gas.

A natural gas appliance cannot be used with LP gas, and an LP gas unit cannot be used with natural gas. Also, ventfree units cannot be converted from one gas type to the other, so make sure you buy the correct gas type, or a dual-fuel unit.

When using LP gas, the manufacturer recommends using at least a 100-lb tank. This doesn't mean that a small LP heater won't run on a 20 or 40-lb tank, but they won't run very long, and be sure to use a hose with a regulator on it, as that is a requirement.

What about People with Asthma or Allergies?

People with severe asthma, allergies, or hyper-sensitive sense of smell may be sensitive to vent-free heaters. It has been estimated that 2-3% of the population will find vent-free heaters objectionable.

What about Moisture?

When gas is burned, water vapor is released into the air. Approximately one ounce of water is produced for each 1,000 btus of gas burned in one hour. So, for example, a 20,000 BTU heater would produce 20 ounces of water vapor if it burned continuously for one hour. If it burned an average of 6 hours during a 24 hour period, it would add 120 ounces (3.75 quarts, which is almost one gallon) of water vapor to the air each day. In the winter, some extra moisture is usually a good thing. But if you put a vent-free heater in a room that already has a humidity problem, the additional humidity can lead to window fogging or even mold and mildew. Improving the air circulation in the room, and/or using a dehumidifier, can fix this problem.

Can I Replace My Central Heating System with Vent-Free Heaters and Fireplaces?

Vent-free heaters are intended to be “supplemental” heat. Most states do not permit the use of vent-free heat sources as the primary source of heat in a home. But if you have an addition to the home, or a cold room, or if you want to cut your overall energy costs by turning the main house thermostat down and adding supplemental heat to the rooms you use the most, vent-free heaters are an excellent choice. Check with your local building inspector to find out what the building codes in your area require.

Are Vent-Free Heaters Legal in All States?

Vent-free heaters are legal in most states. They are not legal in California, and several other states have partial restrictions based upon age of home, city, county, or other factors. Call your local zoning board – they will know the laws for where you live.

Thermostats - What are they and How do they Work?

All Procom and Kozy World fireplaces come with built-in thermostats. Wall heaters typically can be ordered with or without a built-in thermostat. All of these thermostats are built into the unit. They cannot be hooked up to an external wall thermostat (some other gas fireplaces use a different type of gas valve that can be controlled by an external thermostat, but they are typically much more expensive). The thermostat turns the heater or fireplace on and off to maintain a fairly consistent room temperature. Most Procom and Kozy world models have a 'comfort range' thermostat, meaning there is a knob with markings from 1 to 5, 1 being the coolest and 5 the hottest. A setting around 2 or 2.5 will typically keep a room around 70 degrees.

The range of temperature on these thermostats, according to the manufacturer, is as follows: the lowest setting will correspond to a temperature of around 50-55 degrees. The highest setting corresponds to a temperature of about 85 degrees.

The thermostats are typically located at the bottom of the heater, where it measures the temperature of the incoming air.

Altitude Restrictions for Ventfree Appliances

Manufacturers of ventfree appliances typically recommend not using their products above 4,500 or 5,000 feet. This does not mean that the units will not work at higher altitudes necessarily, but the higher you go, the more likely you will run into problems. And at very high altitudes, it can be dangerous to attempt to use ventfree heaters due to incomplete combustion of the gas caused by the low oxygen level. At high altitudes, you need to use vented heaters that have been specially adapted for use at that altitude (see for vented heaters).

Procom and Kozy World heaters and fireplaces all contain an oxygen depletion sensor (ODS). The purpose of the ODS is to shut off the supply of gas to the heater/fireplace when the oxygen level in the room drops below a certain level, typically around 18%. If the pilot light goes out, it will also shut off the gas supply. At sea level, air contains 21-22% oxygen. It is very unlikely that a heater or fireplace would be able to drop the oxygen level to 18% because the air in the room is constantly being replenished by the normal breathing of your home. At higher altitudes, the oxygen content decreases, so not as much oxygen needs to be burned (by the heater) to drop the oxygen level to 18%. So the frequency of ODS shutdowns increases. At some altitude (I think 10-12,000 feet), the oxygen level is at or below 18%, so most ventfree heaters would not even start, or if they did start, they would shut down almost immediately.

The ODS should not be tampered with, as it is there for a reason. Humans can breathe just fine at 18% oxygen level. At lower levels, we can experience difficulty catching our breath, and at much lower levels, suffocation can occur. In addition, trying to burn gas at extremely low oxygen levels can result in incomplete combustion of the gas, which can cause deadly gases and higher levels of carbon monoxide. The ODS will not allow you to use the heater under these conditions, so this is not a problem.

Many people do use ventfree heaters at 6,000, 7,000 and 8,000 feet. The owners manual recommends against doing this, though the wording appears to read as a caution rather than a demand. You may experience more frequent shutdowns of the unit at these altitudes, so don't call Customer Service and report this as a problem, as the unit is doing what it is supposed to be doing - keeping you safe.

Wonder how the ODS works? It is an ingenious design that is virtually foolproof. Gas valves are normally closed. It takes a small electric current to open the valve. Procom and Kozy World use a device called a thermocouple which, when heated by the pilot flame, produces a small electric current. The pilot light burns at about a 45-degree angle and the tip of the flame touches the thermocouple. When the thermocouple reaches a certain temperature, it produces just enough electrical current to keep the gas valve open. This is why, when first starting the pilot, you need to press and hold the gas knob for about 30 seconds. When you press the control knob, you force the gas valve open. Once the pilot lights, it takes several seconds for the flame to heat the thermocouple to the point where it is producing enough current to keep the gas valve open. If you let go of the control knob before the thermocouple is heated, the gas valve will close. Once heated, you can let go and the valve will stay open. If the pilot goes out, the thermocouple cools, the electricity is no longer produced, and the spring-loaded gas valve closes. If the pilot light stays lit, but the oxygen level drops in the room, the pilot light will not burn as strongly, so will not fully engulf the end of the thermocouple. The thermocouple temperature will drop and it will produce less electricity. At some point (typically around 18% oxygen content), the electrical current will drop to the point where it cannot keep the gas valve open. Then the valve will close and the gas supply will be stopped, and your heater will turn off.

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