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How Wood Stoves are EPA-certified for Clean Burns

Morso Contemporary Wood StoveOne of the challenges when burning wood in a stove or fireplace is achieving a “clean” burn, one that doesn’t send toxic pollution into the air outside.  The Environmental Protection Agency has set minimum standards that manufacturers of these appliances must follow in order for their products to lawfully be sold.

With EPA oversight, homeowners can be assured that any stove or fireplace they buy that’s EPA-certified will have a control built in to reduce pollution.

This control can be either catalytic or non-catalytic technology.  It’s a little complicated, but the basics are easy to understand.  Let’s look at how it works on wood stoves.

Air in the firebox

To reduce pollution, there has to be efficient combustion, which is accomplished by maximizing the mixture of air and fuel.  Air that is controlled by the user (with a valve or lever, for example) is called “primary air.”  Bringing air to a fire in this manner isn’t very efficient, resulting in incomplete burns and combustible gasses going up the flue.  This is a common problem with pre-EPA-certified stoves.

Most certified stoves bring air in through a thin opening above the firebox, making for a better mix of oxygen and fuel.  Increased efficiency is accomplished during a second burning phase in which gasses are burned either by a catalytic combustor or a non-catalytic combustion system.  This is what designates one stove type “catalytic” and another “non-catalytic.”

Wood stoves with catalytic combustors

A catalytic combustor filters smoke, burning it and turning it into heat rather than toxic gas.  These stoves are great heat producers.  The combustor is a ceramic device, variously shaped, with spaces for air to go through it.

A chemical is applied to the combustor’s surface that, when a specific temperature is reached, lowers the smoke’s ignition temperature, causing it to burn.  In other words, using the smoke rather than sending it up the flue.

Wood stoves with non-catalytic systems

In order to receive EPA certification, a stove doesn’t have to use catalytic technology.  There are other ways to achieve certifiable efficiency.  Non-cat stoves, as they’re commonly called, contain a secondary air system to initiate combustion.  The key is for the air to be injected in strategic places.

Commonly this is done with stainless steel tubes with holes or another similar device that runs along the top of the firebox.  The air from the tubes mixes effectively with gasses coming up from the burning wood and creates combustion of the gasses.  The user of the stove doesn’t control this process.  It is efficient, even at very low burn rates.

What is the best technology?

vermont castings wood stoveIn a nutshell, catalytic stoves typically have longer burn times, are more efficient and hotter, do well with low burn cycles and need more maintenance.  Non-cat stoves burn brighter fires and are usually less complicated to operate and maintain.

Hudson Valley Chimney wants to help you get the best home heating appliance to meet your needs.  Bring us your questions about EPA-certified stoves.  Our retail store, Ashleigh’s Heath & Home, is at 3647 Albany Post Road in Poughkeepsie.  You can reach us by phone at (845) 471-0789.

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