Airborne debris indoors (C) Daniel Friedman Fireplace & Woodstove Indoor Air Quality Improvement Guide

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Fireplace or woodstove odors, smells, & dust or soot problems in buildings:

This article explains the impact of fireplaces or woodstoves on indoor air quality in homes. We explain what causes these complaints and we describe how to prevent them.

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Guide to Fireplaces & Woodstoves as Sources of Indoor Air Pollutants

Smoky fireplace (C) D FriedmanThis article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. According to Best Practices Guide to Residential Construction :

Traditional open fireplaces and older leaky woodstoves burn very inefficiently and produce hundreds of chemical compounds, including carbon monoxide, organic gases, particulates, and some of the same cancer-causing agents found in tobacco smoke.

Minor spillage of these pollutants occurs regularly, primarily when starting or stoking the fire.

However, the larger concern is when the fire smolders late at night, producing high levels of CO and a weak draft. Backdrafting at this time can be dangerous or even fatal.

Another problem, particularly with fireplaces, is created when the fire is roaring and drawing up to 400 cfm of combustion air.

At this point, its voracious appetite for air can cause backdrafting in other combustion appliances such as a gas water heater.

Also, the need to reheat all the makeup air drags down the fireplace’s heating efficiency to less than 15% and, if the fireplace is allowed to smolder all night, it becomes a net heat loser.

Jotl wood stove installation (C) Daniel Friedman Paul GalowThe Jotul woodstove shown at left was traded for a wristwatch. The new owner installed the stove including a fireproof tile-covered barrier between the stove and a nearby building wall. The owner later added the metal heat reflector to the right of the stove to adjust room comfort and heat movement.

Photo courtesy Paul Galow. That woodbox is too close - less than 36" from the woodstove.

Woodstove efficiency has improved dramatically in response to EPA emissions standards (begun in 1988 and updated in 1990), which apply to most freestanding wood stoves and to fireplace inserts with air-supply controls and tight-fitting doors.

To meet these standards, manufacturers use either a catalytic converter, similar to the ones used in cars, or a reengineered firebox.

The new fireboxes have primary and secondary combustion zones capable of reaching system efficiencies of 60% or more and reducing combustion air intake to as little as 10 cfm. If installed with an outdoor air supply, these can be successfully de- coupled from household air pressures.

While many fireplaces are fitted with glass doors, and some have outside air intakes, nearly all of the glass doors leak air. Even with low levels of depressurization, these fireplaces can still backdraft, and the fireplace’s outdoor air supply might become the makeup air for the kitchen range hood or other exhaust fans, drawing fireplace fumes along with it. The best solution is an airtight fireplace insert.

How to minimize pollution, indoors and outside, from wood-burning appliances

Fireplace with screen (C) D Friedman

  • Choose a properly sized stove or insert certified as meeting EPA emissions standards.
  • Make sure the door gaskets are in good shape, the doors fit tightly, and the stove is free of air leaks.
  • Make sure the flue is the correct diameter and height, and have it inspected and cleaned annually.
  • Use wood that has been split and dried for at least six months. Try to use small pieces, and do not overload the firebox. Leave enough room for air to circulate freely around the wood.
  • For safety purposes, install a smoke alarm and carbon monoxide detector in the same room as the woodstove or fireplace.

-- Adapted with permission from Best Practices Guide to Residential Construction.

Watch out: several of our clients report, and tests confirmed horrible building odor problems after excessive use of ozone as a "cure" for fireplace or woodsmoke or creosote odors in buildings.

Excessive or improper use of ozone as an "odor killer" in such situations can lead to oxidation of other building materials that then give off chemical or plastic odors that cannot be cured without removing and replacing the materials affected.

See OZONE HAZARDS for details.


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