Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
CSA CAN1-12.4-M84 (2018): Non-Recirculating Direct Gas-Fired Industrial Air Heaters – Technical Requirements and Compliance
A comprehensive guide to the Canadian standard for direct gas-fired heating equipment used in industrial and commercial spaces.
CSA CAN1-12.4-M84 (2018) is a long-standing Canadian standard that specifies construction, performance, and safety requirements for non-recirculating direct gas-fired industrial air heaters. Originally published in 1984 and reaffirmed in 2018, this standard remains a key reference for manufacturers, engineers, and regulatory authorities across Canada. The heaters covered by this standard are used for space heating in large industrial and commercial buildings where combustion products are diluted with heated make-up air before being discharged into the occupied space.
Scope and Application
This standard applies to factory-built, automatically operating, non-recirculating direct gas-fired air heaters that use natural gas, propane, or manufactured gases for combustion. The heaters are designed for indoor installation in non-hazardous (ordinary) locations and shall not incorporate recirculation of building air through the burner zone. Typical applications include warehouses, manufacturing plants, loading docks, and garages where high volumes of tempered fresh air are required.
The standard covers heaters with input capacities up to 2000 kW (6.8 million Btu/h) and provides criteria for safe operation under all normal ambient conditions. It does not cover direct-fired heaters that recirculate return air, gas-fired unit heaters, or appliances intended for outdoor installation.
Tip: When specifying a non-recirculating heater for a new facility, always verify that the ventilation design maintains at least 10% outdoor air to ensure adequate combustion air and acceptable indoor air quality.
Key Technical Requirements
Construction and Materials
All heaters must be constructed of non-combustible materials for the heat exchanger, burner, and casing. The standard requires that the external surfaces be of corrosion-resistant metal or coated steel. Removable access panels are mandatory for inspection and cleaning. Minimum clearances from combustible construction must follow the values in Table 1.
| Heater Input (kW) | Top / Back / Sides | Flue Outlet | Front (Service Side) |
|---|---|---|---|
| ≤ 150 | 150 | 450 | 600 |
| 150 – 600 | 300 | 600 | 900 |
| 600 – 2000 | 450 | 750 | 1200 |
Gas Train and Safety Controls
The gas train must include a manual shutoff valve, a gas pressure regulator, a safety shutoff valve (redundant for inputs above 300 kW), and a leak-tight valve proving system. The standard mandates the following safety controls as minimum:
- Flame safety system (flame rod or ultraviolet sensor) that shuts off gas within 4 seconds of flame loss.
- High-temperature limit switch to prevent overheating.
- Airflow proving switch interlocked with gas supply.
- Ignition system that interrupts gas if not proven within 4 seconds.
Warning: A heater that recirculates building air through the burner can cause unsafe accumulation of combustion by-products. CAN1-12.4-M84 strictly prohibits recirculation designs; use a separate make-up air unit if tempered recirculation is required.
Combustion and Ventilation Performance
Heaters must deliver a minimum combustion efficiency of 80 % when measured at rated input. Carbon monoxide (CO) emissions in the undiluted flue gas must not exceed 200 ppm (corrected to 0 % O2). The temperature rise across the heater shall not exceed 55 °C when the air temperature at the heater outlet is less than 65 °C. The standard also includes detailed test methods for verifying airflow, gas input, and flue gas discharge rates.
Implementation and Compliance Notes
Compliance with CSA CAN1-12.4-M84 is typically demonstrated through product certification by an accredited agency such as CSA Group, Intertek (UL), or Underwriters Laboratories of Canada (ULC). Authority Having Jurisdiction (AHJ) across Canada often requires that installed heaters bear a certification mark confirming compliance with this standard.
Success: Using a certified heater simplifies site acceptance by building inspectors and reduces liability. Always request the certificate of compliance from the manufacturer for each model.
Field Modifications and Maintenance
The standard discourages any field modification that may affect safety, such as altering the gas orifice size, bypassing safety interlocks, or changing the airflow path. If modifications are necessary, they must be reviewed by the certifying body. Annual inspection of the heat exchanger, gas train, and control wiring is recommended to maintain conformance.
Frequently Asked Questions
Q: Can a non-recirculating direct gas-fired heater be used in a hazardous (classified) location?
A: No. CSA CAN1-12.4-M84 is intended only for ordinary (non-hazardous) locations. For environments with flammable vapors or dusts, refer to CSA C22.2 No. 0 or other relevant hazardous location standards.
A: No. CSA CAN1-12.4-M84 is intended only for ordinary (non-hazardous) locations. For environments with flammable vapors or dusts, refer to CSA C22.2 No. 0 or other relevant hazardous location standards.
Q: What distinguishes a non-recirculating direct gas-fired heater from a unit heater?
A: A non-recirculating heater uses fresh outdoor air for combustion and mixes all combustion products with the heated air. A unit heater, by contrast, typically uses a sealed combustion system or a heat exchanger and recirculates indoor air over it. The two appliance types follow different safety codes.
A: A non-recirculating heater uses fresh outdoor air for combustion and mixes all combustion products with the heated air. A unit heater, by contrast, typically uses a sealed combustion system or a heat exchanger and recirculates indoor air over it. The two appliance types follow different safety codes.
Q: Is the 2018 reaffirmation identical to the 1984 edition?
A: The 2018 reaffirmation confirms the technical requirements of the original 1984 edition with minor editorial updates. No substantive changes were introduced, ensuring continuity for manufacturers and regulators.
A: The 2018 reaffirmation confirms the technical requirements of the original 1984 edition with minor editorial updates. No substantive changes were introduced, ensuring continuity for manufacturers and regulators.
Adherence to CAN1-12.4-M84 (2018) provides a proven framework for the safe design and deployment of non-recirculating direct gas-fired industrial air heaters. By meeting its construction, performance, and safety criteria, stakeholders can ensure reliable heating solutions that comply with Canadian regulations and protect building occupants.
© 2026 — Technical Overview of CSA CAN1-12.4-M84 (2018). This article is for informational purposes and does not replace the official standard.