Since 15 May 2020 it has been unlawful in the United States to sell a new residential wood heater that is not certified to the EPA New Source Performance Standards Step 2 limits. The obligation falls on the seller, not just the manufacturer. That is why every product page here carries the certification data.
The limits
- 2.0 g/h particulate matter when tested with crib wood
- 2.5 g/h particulate matter when tested with cord wood
Cord wood is the realistic test — it is what people actually burn. A stove listed here at, say, 1.6 g/h is comfortably inside the limit.
What the other numbers mean
- Average overall efficiency (HHV) — how much of the fuel’s energy reaches the room, measured against the higher heating value. Anything in the high 60s to mid 70s is good for a non-catalytic stove.
- Average carbon monoxide — a second indicator of how completely the stove burns. Lower is cleaner.
- EPA loading volume — the firebox volume used in the certification test, which is smaller than the physical firebox.
- Combustion technology — catalytic, non-catalytic or hybrid. Catalytic stoves burn cleaner at low output but the combustor is a wearing part.
Exempt appliances
A few appliances, principally some cookstoves, fall outside the NSPS wood heater definition and are marked EPA exempt rather than certified. That is a legitimate status, not a gap in the paperwork.
Where to check for yourself
The EPA publishes a searchable database of every certified wood heater at cfpub.epa.gov/oarweb/woodstove/. The certification number for your appliance is on the permanent label attached to it, and the certificate ships with the stove.
Older stoves
Owning an uncertified stove is legal. Selling one is not. If you are replacing an older appliance, check whether your state or air district runs a change-out rebate — several do, and they can be worth several hundred dollars.