For millions of homes and commercial buildings across North America, gas-fired central furnaces remain a primary source of reliable indoor heating. As furnace technology continues to evolve to meet modern performance expectations, manufacturers, testing laboratories, regulators, and HVAC professionals can adhere to standards to assure these systems operate safely and effectively. CSA/ANSI Z21.47-26/CSA 2.3-2026: Gas-fired central furnaces establishes requirements for gas-fired central furnaces intended for residential, commercial, and industrial applications.
What Is a Gas-Fired Central Furnace?
CSA/ANSI Z21.47-26/CSA 2.3-2026 defines a gas-fired central furnace as “a self-contained, gas-burning appliance for heating air by transfer of heat of combustion through metal to the air, and designed to supply heated air through ducts to spaces remote from or adjacent to the appliance location.”
Essentially, a gas-fired furnace is a heating appliance that burns natural gas or propane to generate heat. The heat produced during combustion is transferred through a heat exchanger, where air is warmed and then distributed throughout a building using a blower and ductwork system. Modern gas-fired furnaces are available in a variety of configurations and efficiency levels, ranging from standard-efficiency units to high-efficiency condensing furnaces that capture and utilize additional heat from combustion gases before they are vented outdoors. Since gas-fired furnaces involve fuel combustion, ignition systems, venting components, and electrical controls, their design and operation must meet strict safety and performance requirements.
What Is CSA/ANSI Z21.47-26/CSA 2.3-2026?
CSA/ANSI Z21.47-26/CSA 2.3-2026 is the ninth edition of the binational standard governing automatically operating gas-fired central furnaces. It applies to automatically operating gas-fired central furnaces for installation in residential, commercial, and industrial structures, including furnaces for direct vent, recreational vehicle, outdoor, and manufactured (mobile) homes. The furnaces in the scope of this American National Standard can include a cooling unit; this standard assumes that all units are constructed entirely of new and unused parts and materials.
Types of Central Furnaces Addressed in CSA/ANSI Z21.47-26/CSA 2.3-2026
CSA/ANSI Z21.47-26/CSA 2.3-2026 addresses furnaces classified as:
- Category I — a central furnace that operates with a non-positive vent static pressure and with a flue loss not less than 17%.
- Category II — a central furnace that operates with a non-positive vent static pressure and with a flue loss less than 17%.
- Category III — a central furnace that operates with a positive vent static pressure and with a flue loss not less than 17%.
- Category IV — a central furnace that operates with a positive vent static pressure and with a flue loss less than 17%
These categories represent different venting and combustion characteristics that impact furnace design, installation, and performance requirements.
What Are the Changes in CSA/ANSI Z21.47-26/CSA 2.3-2026?
CSA/ANSI Z21.47-26/CSA 2.3-2026 supersedes the previous edition published in 2021. The following are the major changes to this edition:
- Manufactured gas and mixed gas types have been removed
- Clause 4.6.13, “Treatment of copper tubing for gas conveyance,” has been added to address specific installation conditions
- The requirements in Clause 4.10.1, “Compliance of automatic gas ignition systems and components,” have been updated to reflect revisions to ANSI Z21.20, particularly those regarding ignition control system standards
- The test method in Clause 4.14.14.2, “Venting System Components, Method of test,” has been revised to accommodate changes in non-metallic venting standards
- Clause 4.23.2, “Safety information requirements for furnace installation manuals,” has been revised to clarify instructions related to the installation manual requirements
- Clause 4.25, “User’s information manual,” has been updated to address additional safety and performance requirements
- A formula has been added to Clause 5.8.1.2, “Combustion, Pressure and input variations, Method of test,” to assist in determining the correct procedure for computing air-free CO
- The minimum temperature requirement has been removed from Clause 5.17, “Allowable heating element temperatures”
- Clauses 5.36.6, “Furnace subjected to a simulated rainstorm,” and 7.4.5, “Air intake or vent outlet blockage test,” have been removed from the Standard
- Clause 13.1, “Items unique to Canada, Instructions” has been removed
- Table 10, “Characteristics of test gases,” has been updated to align with the latest gas composition standards
- Table 11, “Inlet test pressures,” has been revised for consistency with current industry practices
- The test device and average free-stream pressure values in Figure 17, “Wind source calibration procedure test device and average free-stream pressure values,” have been updated
- New Normative Annex S, “Formula for calculation of input for furnaces,” has been added to provide a standardized formula for furnace input calculations.
This latest edition of CSA/ANSI Z21.47-26/CSA 2.3-2026 serves as an important benchmark for manufacturers seeking product certification and market access throughout the United States and Canada.
The Role of Natural Gas in Home Heating Across the U.S.
The continued importance of gas-fired furnaces is reflected in residential heating trends across the United States. Natural gas remains the dominant home heating fuel in many densely populated regions and metropolitan areas, particularly throughout the Midwest, West, and portions of the Northeast.
The widespread use of natural gas heating underscores the importance of standards such as CSA/ANSI Z21.47-26/CSA 2.3-2026, which helps assure that gas-fired central furnaces are designed, tested, and certified to meet modern safety and performance requirements for homes and commercial buildings across North America. As energy efficiency, emissions reduction, and occupant safety continue to be priorities for building owners and regulators, adherence to recognized furnace standards plays an increasingly important role in supporting reliable heating system performance.
Where to Find CSA/ANSI Z21.47-26/CSA 2.3-2026
CSA/ANSI Z21.47-26/CSA 2.3-2026: Gas-fired central furnaces is available on the ANSI Webstore.
CSA/ANSI Z21.47-26/CSA 2.3-2026 was developed by CSA Group.
Please direct any technical questions relating to this American National Standard to the developer. You can find the contact information for all ANSI-accredited standards developers here: List of ANSI-Accredited Standards Developers (ASDs).
For further information, please refer to: Who to Contact for Standards Related Questions.