For original equipment manufacturers (OEMs) designing commercial and industrial heating equipment, understanding ANSI safety standards is an essential part of burner selection, equipment development, and product certification. Three important standards—ANSI Z83.4, ANSI Z83.18, and ANSI Z83.25—address different types of direct gas-fired heating systems used in make-up air, ventilation, and industrial process heating applications.
Although these standards share certain safety and performance requirements, they apply to different equipment configurations, operating conditions, and intended uses. Selecting the appropriate standard early in the design process can help OEMs avoid costly modifications, simplify certification testing, and develop heating equipment that meets applicable requirements.
At Midco International, we work with OEMs to develop customized gas burner solutions for make-up air units, industrial ventilation equipment, process heating systems, and specialized heating applications. Our engineering expertise and in-house testing capabilities help manufacturers address combustion performance, emissions, and certification requirements.
Why Do ANSI Standards Matter for Make-Up Air and Process Heating Equipment?
Direct gas-fired heating systems introduce combustion heat directly into the moving air stream. Unlike indirect-fired systems that use a heat exchanger, direct-fired equipment allows combustion products to enter the heated airflow.
This design can provide efficient heat transfer, rapid temperature response, and flexible heating capacity. However, it also requires careful attention to combustion quality, airflow, temperature limits, safety controls, and emissions.
ANSI standards establish requirements intended to support safe and consistent equipment operation.
For OEMs, identifying the correct standard affects several important design considerations:
- Whether the system uses 100% outdoor air or recirculated air
- The equipment’s intended heating application
- Maximum allowable discharge temperatures
- Burner combustion performance and emissions
- Airflow monitoring and safety controls
- Certification testing and documentation
Understanding these differences before selecting a burner or finalizing equipment specifications can reduce development challenges later in the manufacturing process.
What Is ANSI Z83.4?
ANSI Z83.4 covers non-recirculating direct gas-fired heating and forced ventilation appliances used in commercial and industrial applications.
These systems use 100% outdoor air that passes through the heating equipment before being supplied to the building.
ANSI Z83.4 is commonly associated with direct-fired make-up air units designed to replace air removed by exhaust fans, ventilation systems, and industrial processes.
Typical applications include commercial ventilation systems, industrial facilities, warehouses, manufacturing buildings, and other operations requiring large volumes of replacement air.
Equipment covered by this standard is generally designed for heated discharge air temperatures of 160°F or less.
For OEMs developing non-recirculating make-up air equipment, important considerations include maintaining proper airflow through the burner, controlling discharge temperatures, monitoring combustion performance, and integrating required safety systems.
Because the system uses outdoor air rather than recirculating indoor air, ANSI Z83.4 is often an appropriate starting point for manufacturers designing conventional direct-fired make-up air units.
What Is ANSI Z83.18?
ANSI Z83.18 addresses recirculating direct gas-fired heating and forced ventilation appliances for commercial and industrial applications.
Unlike non-recirculating equipment, these systems combine outdoor ventilation air with air returned from the building.
Recirculation can help reduce heating demand by reusing a portion of the already heated indoor air. However, because direct-fired equipment introduces combustion products into the supply air, recirculation requires additional consideration of indoor air quality and combustion emissions.
A common equipment configuration uses approximately 80% recirculated air and 20% outdoor air, although the actual operating arrangement must satisfy the applicable standard and system requirements.
ANSI Z83.18 equipment is generally limited to heated discharge air temperatures of 160°F or less.
For OEMs, the design process must account for outdoor air requirements, recirculation controls, combustion performance, airflow monitoring, and safe operating conditions.
The distinction between ANSI Z83.4 and ANSI Z83.18 is particularly important when determining whether a make-up air unit will operate entirely on outdoor air or incorporate recirculation.
What Is ANSI Z83.25?
ANSI Z83.25 covers direct gas-fired process air heaters used primarily for process heating in commercial and industrial environments.
Unlike conventional make-up air equipment designed mainly for building ventilation and temperature control, process air heaters provide heat for specific manufacturing or industrial operations.
These systems may use recirculating or non-recirculating airflow, depending on the application and operating requirements.
ANSI Z83.25 permits maximum discharge temperatures of up to 250°F for equipment within its scope.
Common applications include automotive spray booths, industrial finishing operations, and specialized process heating systems.
For example, an automotive paint booth may require ventilation during occupied spray operations and higher-temperature heating during an unoccupied curing cycle. Equipment designed for these operating conditions must address the applicable ventilation, temperature, combustion, and safety requirements.
OEMs developing process heating equipment should evaluate whether their system falls within ANSI Z83.25 rather than assuming that a conventional make-up air standard applies.
ANSI Z83.4 vs. Z83.18 vs. Z83.25: What’s the Difference?
| ANSI Standard | Equipment Type | Airflow Configuration | Maximum Discharge Temperature |
|---|---|---|---|
| ANSI Z83.4 | Non-recirculating direct gas-fired heating and ventilation | 100% outdoor air | 160°F |
| ANSI Z83.18 | Recirculating direct gas-fired heating and ventilation | Outdoor air and recirculated air | 160°F |
| ANSI Z83.25 | Direct gas-fired process air heating | Recirculating or non-recirculating | 250°F |
These distinctions provide a useful starting point, but the correct standard must be determined by the equipment’s complete design, intended application, operating conditions, and applicable edition of the standard.
What Do OEMs Need to Consider During ANSI Certification Testing?
Certification involves more than demonstrating that a burner can generate the required heating capacity.
The complete heating appliance must be evaluated for applicable safety and performance requirements.
Depending on the standard and equipment configuration, testing may address airflow measurement, high-temperature limit controls, airflow sensing systems, operating temperature controls, combustion performance, ignition systems, burner operating characteristics, and electrical safety.
Carbon monoxide (CO) and nitrogen dioxide (NO₂) emissions are particularly important considerations for direct gas-fired equipment because combustion products enter the heated air stream.
OEMs should also consider how burner modulation, airflow changes, temperature rise, and control system operation affect performance throughout the equipment’s operating range.
Early collaboration between the burner manufacturer and equipment engineering team can help identify potential issues before formal certification testing begins.
How Does Burner Selection Affect ANSI Compliance?
Selecting the right burner is a critical part of designing direct gas-fired heating equipment.
A burner must provide the required heating capacity while operating reliably within the airflow, temperature, emissions, and control requirements of the complete system.
For make-up air and process heating OEMs, important burner selection factors include heating capacity, available installation space, airflow characteristics, turndown ratio, combustion stability, emissions performance, and compatibility with the equipment’s control system.
A burner that performs well in one application may require different engineering considerations when integrated into a recirculating heater or higher-temperature process heating system.
Midco International’s HMA direct-fired make-up air burner solutions are designed for commercial and industrial heating applications. Our engineering team works with OEMs to evaluate burner configurations, heating requirements, and equipment integration.
By addressing burner performance and certification requirements together, manufacturers can develop heating equipment that meets application-specific demands.
How Can Midco International Help OEMs With ANSI Testing and Certification?
Midco International provides engineering support, burner customization, and in-house product certification testing for OEM customers developing gas-fired heating equipment.
Our Chicago-based engineering and testing capabilities support manufacturers working with ANSI Z83.4, ANSI Z83.18, and ANSI Z83.25 requirements.
Midco’s services include burner integration, equipment evaluation, combustion and emissions testing, engineering documentation, and support through applicable ETL certification testing.
Our laboratory is equipped to evaluate important performance characteristics, including CO and NO₂ emissions, airflow, and operating conditions.
Working directly with OEM engineering teams allows Midco to identify potential design challenges, evaluate burner configurations, and support equipment development before production.
Whether the application involves a non-recirculating make-up air unit, a recirculating industrial heater, or a specialized process heating system, Midco provides technical expertise to help manufacturers move from initial design toward certification.
Frequently Asked Questions About ANSI Standards for Gas-Fired Heating Equipment
What is the main difference between ANSI Z83.4 and ANSI Z83.18?
ANSI Z83.4 applies to non-recirculating direct gas-fired heating and ventilation equipment using outdoor air. ANSI Z83.18 addresses equipment that combines outdoor ventilation air with recirculated building air. Both standards cover commercial and industrial applications with discharge temperature limits generally reaching 160°F.
When should an OEM consider ANSI Z83.25?
ANSI Z83.25 should be evaluated when designing direct gas-fired equipment intended primarily for industrial process heating rather than conventional building ventilation. Applications such as automotive paint booth curing may fall within its scope, depending on equipment design and operating conditions.
Can a direct-fired make-up air burner be used in different ANSI applications?
Potentially, yes. However, the burner must be suitable for the intended operating conditions, and the complete heating appliance must satisfy the applicable standard. Burner selection alone does not establish equipment certification.
Why are CO and NO₂ emissions important in direct-fired heating systems?
Direct-fired systems introduce combustion products into the heated airflow. Monitoring and controlling carbon monoxide and nitrogen dioxide emissions is therefore an important part of equipment safety, combustion performance, and applicable certification testing.
Does ANSI certification apply to the burner or the complete heating unit?
The ANSI Z83 standards discussed here generally address complete heating appliances. A burner may be designed to support compliance, but the assembled equipment must undergo the required evaluation and certification process.
Can Midco International help OEMs prepare for ANSI certification?
Yes. Midco International provides engineering support, custom burner integration, and in-house testing capabilities for manufacturers developing make-up air and process heating equipment. Our team can help evaluate system requirements and support applicable certification testing.
Partner With Midco International for Make-Up Air and Process Heating Solutions
Understanding ANSI Z83.4, Z83.18, and Z83.25 is an important step in developing safe, reliable, and properly engineered direct gas-fired heating equipment.
For OEMs, selecting the appropriate standard early in the design process can help streamline burner integration, improve equipment performance, and reduce potential certification challenges.
Midco International combines decades of combustion engineering experience with customizable burner technology and in-house testing capabilities to support commercial and industrial equipment manufacturers.
Whether you’re developing a new make-up air unit, designing a recirculating heating system, or engineering specialized process heating equipment, our team can help evaluate the burner and certification requirements for your application.
Contact Midco International today to discuss your OEM heating project, explore our HMA burner solutions, and learn