A new wood stove sold today has to meet EPA's Step 2 limit of 2.0 grams of particulate smoke per hour, which took effect in May 2020. Look for the EPA label on the back of the stove, and compare models on the grams per hour printed on the label: lower is cleaner.
What the standard limits
EPA sets a mandatory smoke emission limit for new wood-burning room heaters, measured in grams of particulate smoke per hour (g/h). Under Step 1 of the revised standards the limit was 4.5 g/h. Step 2 took effect in May 2020, lowering the limit to 2.0 g/h. EPA notes that some newer stoves have emission ratings in the 1 to 4 g/h range, so the figure on the label still separates models.
For comparison, EPA's archived Burn Wise program puts older uncertified stoves at 15 to 30 grams of smoke per hour. That gap is the reason the rules exist: wood smoke carries fine particles, and EPA's health guidance links that pollution to breathing and heart problems, especially for children, older adults and people with lung disease.
How to read the label and the listing
The EPA certification label sits on the back of the stove. It states the emission rate the stove achieved in its certification test. Listings repeat it in different ways: a '2020 EPA' badge, 'meets 2020 EPA standards' or a figure such as '1.9 g/hr'. When a listing gives a number, it is the more useful figure; when it only names the standard, the stove still has to meet 2.0 g/h to be sold new.
Where a listing states its grams per hour, our product pages show it next to the heating area.
Efficiency is a separate figure. Some makers state it as a percentage of the wood's heat that reaches the room; others don't state it at all. A low grams-per-hour figure and a high efficiency often go together, because both come from burning the gases that an older stove sends up the chimney.
Catalytic and non-catalytic designs
EPA describes two ways stoves meet the limit. Non-catalytic stoves insulate the firebox, use a large baffle for a longer, hotter gas path, and feed pre-heated air through small holes above the fire. Catalytic stoves pass the smoke through a coated honeycomb that lets it burn at a lower temperature; they have a bypass damper that is opened for starting and reloading. Most stoves on the market are non-catalytic, while some popular high-end stoves are catalytic.
EPA notes that a catalyst can last more than six seasons when the stove is used properly, and that over-firing or burning garbage and treated wood shortens its life. Our guide to catalytic and non-catalytic stoves compares the two in more detail.
What the rules mean for a used or older stove
The standard applies to new stoves when they are made and sold. It does not reach into a stove already installed in your home. What it means in practice is that a pre-1990s stove is likely to fall in EPA's 15 to 30 g/h range, burns more wood for the same heat and smokes more. Local rules can go further, for example restricting burning on poor air quality days or requiring removal of uncertified stoves when a house is sold, so check with your local air agency before buying or keeping an old stove.
A federal tax credit used to help with replacement: the IRS energy-efficient home improvement credit allowed up to $2,000 a year for biomass stoves with a thermal efficiency of at least 75%, for property placed in service through the end of 2025. That window has closed.
Burning to the standard at home
A stove only performs near its label figure when it burns fuel like the fuel it was rated on. EPA's guidance: burn only dry, split, well-seasoned wood, season it for at least six months, and burn it at a moisture content under 20 percent. Build hot fires and keep the door closed except when loading or stoking. Never burn household trash, cardboard, plastics, foam or coloured-ink paper.
- Check the label for the emission rate before you buy.
- Ask for the efficiency figure if the listing doesn't state it.
- Plan your wood supply a season ahead so it is dry when you burn it.