ANSI Z21.11.2: What a Vent-Free Certification Covers
ANSI Z21.11.2 is the unvented room heater standard. What a listing on the label actually certifies, what it does not, and how to check your own unit.
International Fuel Gas Code
Ventless Fireplace BTU Rating Explained: The Data Plate
What the BTU rating on a vent-free fireplace data plate means, why it is an input figure, and what else on that plate decides whether a unit fits.
Ventless Fireplace BTU and Room Size: The Real Limits
Ventless fireplace BTU and room size: why per-square-foot rules of thumb are not a safe substitute, and the three places the real limits come from.