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List of State Officials - Martin O'Malley, Governor; Anthony Brown, Lt. Governor; Shari T. Wilson, MDE Secretary 

Volume IV, Number 3

 February 2010

eMDE is a quarterly publication of the Maryland Department of the Environment. It covers articles on current environmental issues and events in the state. 

MDE Takes Steps to Promote Cleaner Burning of Wood for Home Heating

By Randy E. Mosier, Air and Radiation Management Administration

Back to this issue's cover page 

Maryland has adopted new regulations that establish improved operating and emission standards to promote the use of clean and efficient small wood boilers.

With the high cost of home heating, more Marylanders might be looking to wood as a source of heat and hot water. However, wood may not provide a clean, efficient energy source. Home wood burning systems come in many forms, though the most popular are indoor wood or pellet stoves, fireplace inserts, and, more recently, small wood boilers. While indoor wood stoves and fireplace inserts have long been tested for emissions and certified by the U.S. Environmental Protection Agency, testing and certification of small wood boilers has only recently begun.

A wood boiler is a furnace, boiler, or stove designed to burn wood for heating and hot water needs. These units vary in size from 115,000 to 3.2 million British thermal units (Btu) per hour. While they may be placed indoors, they are most often located in a separate, self-contained shed with a smoke stack. This shed protects a firebox surrounded by a water jacket in which water is heated then pumped through underground pipes to homes, shops, swimming pools, spas, or any application that requires heat or hot water. While the fundamental design of a wood boiler maximizes the transfer of heat to the water, wood boilers that do not have any emission controls may contribute to a significant source of air pollution and other environmental and health problems, which include:

  • Particle matter and toxic compound emissions (carbon monoxide, formaldehyde, benzene, and naphthalene) that cause and contribute to serious health problems for people exposed to excessive wood smoke emissions;
  • Excessive particle emissions that impede Maryland’s and other states’ abilities to meet federal air quality standards; and 
  • Foul, heavy smoke that creates a nuisance in many communities where these units are in operation.

Maryland regulations prohibit the sale, distribution and installation of small wood boilers in Maryland that are not certified and labeled to meet the following emission standards:

  • Phase 1: April 1, 2009 through March 31, 2010 - 0.60 pounds of particulate matter per million Btu of heat input
  • Phase 2: April 1, 2010 and after - 0.32 pounds of particulate matter per million Btu of heat output.

Wood boilers purchased or installed before April 1, 2009, are not required to meet the emission standards or certification and labeling requirements in the proposed regulation. However, owners and operators of small wood boilers must follow the operating requirements in the proposed rule, must operate the unit in accordance with manufacturers' instructions, and may not operate the unit in a manner that causes a public nuisance.

Owners and operators of new and existing small wood boilers are required to use only clean wood, wood pellets made from clean wood, or heating oil as fuel and are prohibited from using garbage, tires, asphalt products, manure, and animal carcasses as fuel. Burning waste materials, trash, painted or treated wood, or construction debris in wood boilers can cause a public heath threat by exposing people to toxins.

>For more information visit:

Maryland Small Wood Boilers

Outdoor Wood Furnace Best Burn Practices

Burn Wise


©2010 Copyright MDE

Editorial Board
Maryland Department of the Environment
1800 Washington Boulevard, Baltimore, MD 21230