+---
+title: Gas-Fired Radiant and Infrared Heaters
+category: Mechanical / Air Distribution
+toc_depth: 3
+description: >
+ When to use: gas-fired high-intensity luminous (ceramic/box/spot) and low-intensity
+ radiant tube heaters used as primary or supplemental heating in commercial and
+ industrial high-bay spaces (warehouses, distribution centers, manufacturing floors,
+ aircraft hangars, auto service bays, gymnasiums, loading docks) with ceilings 12 ft
+ and above, where direct radiant delivery to occupants and surfaces is preferred over
+ convective air heating; natural gas or propane, vented or unvented, overhead-,
+ angle-, or wall-mounted.
+ Not intended for: hydronic or electric cabinet/propeller unit heaters (see
+ sync/unit-heaters); baseboard, fin-tube, convectors, or radiant panel terminals
+ (see sync/terminal-heating-units); gas piping upstream of the heater connection
+ (see sync/natural-gas-piping); combustion-air supply and exhaust fans
+ (see sync/hvac-fans); electric resistance quartz/ceramic infrared heaters; outdoor
+ decorative patio heaters; and process ovens, dryers, or industrial curing systems.
+---
+
+# Scope {toc}
+
+## This standard covers the selection, fabrication, connection, controls integration, and commissioning of gas-fired radiant and infrared heaters for commercial and industrial spaces. {note}
+
+## Two heater families are covered, and they are governed by distinct product safety standards that are not interchangeable. {note}
+
+### High-intensity luminous heaters radiate from a glowing ceramic or perforated metal surface at the burner face, are typically unvented, and serve open or partially open spaces such as dock doors, automotive service bays, and spot-heating positions. {note}
+
+### Low-intensity radiant tube heaters radiate from a heated steel tube driven by a remote burner, are typically vented, and serve enclosed warehouse and manufacturing floors. {note}
+
+## Heaters covered here deliver heat primarily by infrared radiation to surfaces and occupants rather than by warming and circulating room air. {note}
+
+## The 80% case for an industrial project is a vented low-intensity straight-tube or U-tube heater, 100,000 to 150,000 BTU/hr, natural gas, two-stage or modulating, mounted at 16 to 24 ft above finished floor in a warehouse or manufacturing bay. {note}
+
+## The following are not within this scope: {note}
+- Hydronic and electric cabinet or propeller unit heaters, addressed in [[sync/unit-heaters]].
+- Baseboard, fin-tube, cabinet convectors, and radiant ceiling or wall panels, addressed in [[sync/terminal-heating-units]].
+- Natural gas and propane piping, regulators, and meter sets upstream of the heater gas connection, addressed in [[sync/natural-gas-piping]].
+- Supply and exhaust fans serving combustion-air ventilation, addressed in [[sync/hvac-fans]].
+- Electric resistance quartz and ceramic infrared heaters, outdoor decorative patio heaters, and industrial process ovens, dryers, and curing systems.
+
+## Heater type, fuel, capacity, configuration, mounting, controls, and combustion-air arrangement shall be selected as required to meet the heating load and the conditions of the served space.
+
+```datasheet
+label: Heater family
+type: radio
+options:
+ - Low-intensity radiant tube (vented, enclosed spaces)
+ - High-intensity luminous (unvented, open or spot heating)
+default: Low-intensity radiant tube (vented, enclosed spaces)
+```
+
+```datasheet
+label: Fuel type
+type: radio
+options:
+ - Natural gas
+ - Propane (LP)
+default: Natural gas
+```
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+## The adopted edition of each code is the one enforced by the authority having jurisdiction; cited editions reflect a common current baseline. {note}
+
+| Standard | Title |
+|----------|-------|
+| ANSI Z83.19 / CSA 2.35-2017 | Gas-Fired High-Intensity Infrared Heaters |
+| ANSI Z83.20 / CSA 2.34-2017 | Gas-Fired Low-Intensity Infrared Heaters |
+| ANSI/AHRI 1330-2024 (SI) | Performance Rating for Radiant Output of Gas-Fired Infrared Heaters |
+| NFPA 54 / ANSI Z223.1-2021 | National Fuel Gas Code |
+| NFPA 1-2021 | Fire Code |
+| ASHRAE 90.1-2022 | Energy Standard for Sites and Buildings Except Low-Rise Residential |
+| IBC-2021 | International Building Code (Chapter 14; structural support) |
+| IMC-2021 | International Mechanical Code (Chapter 10; appliance installation) |
+| NFPA 70 / NEC-2023 | National Electrical Code (Article 422, Appliances) |
+| CSA/ANSI Z83.26 / CSA 2.37-2020 (R2025) | Gas-Fired Outdoor Infrared Patio Heaters (only if outdoor units in scope) |
+
+# Submittals {toc}
+
+## The Contractor shall submit the following action submittals for review before fabrication or delivery:
+
+- Product data for each heater type, including input capacity, fuel type, tube geometry and length, reflector material, ignition type, and electrical characteristics.
+- Manufacturer certification of listing to ANSI Z83.19 (high-intensity) or ANSI Z83.20 (low-intensity) as applicable, including the listing label clearances to combustibles.
+- Radiant performance data per ANSI/AHRI 1330-2024, reporting the Radiant Emission Value (REV) and net radiant efficiency for each model.
+- A heater layout plan showing position, mounting height, tilt angle, coverage pattern, clearances to combustibles, and clearances to obstructions (racking, cranes, mezzanines).
+- Gas connection schematic showing required inlet pressure, manifold pressure, and connection size for each heater.
+- Combustion-air and venting design, including vent material, vent routing to exterior, and termination location for vented units; ventilation rate calculation for unvented units.
+- Wiring diagrams for ignition, controls, staging or modulation, and any building automation system interface.
+- Structural support and hanger details, including connection to roof structure and, where required, seismic bracing and vibration-isolation provisions.
+
+```datasheet
+label: Action submittals required
+type: checkbox
+options:
+ - Product data (each heater type)
+ - Z83.19 / Z83.20 listing certification
+ - AHRI 1330 REV and radiant efficiency data
+ - Heater layout plan with clearances
+ - Gas connection schematic
+ - Combustion-air and venting design
+ - Control and wiring diagrams
+ - Structural support and bracing details
+default:
+ - Product data (each heater type)
+ - Z83.19 / Z83.20 listing certification
+ - AHRI 1330 REV and radiant efficiency data
+ - Heater layout plan with clearances
+ - Gas connection schematic
+ - Control and wiring diagrams
+ - Structural support and bracing details
+```
+
+## The Contractor shall submit the following closeout submittals before substantial completion:
+
+- Installation, operation, and maintenance (IOM) manuals for each heater model.
+- Commissioning report documenting gas pressure verification, ignition checks, staging or modulation verification, and combustion or flue-spillage checks.
+- Manufacturer warranty documentation for heat exchangers, burners, and controls.
+- Record drawings reflecting as-installed heater positions, gas routing, and vent terminations.
+
+```datasheet
+label: Closeout submittals required
+type: checkbox
+options:
+ - IOM manuals
+ - Commissioning report
+ - Warranty documentation
+ - Record drawings
+default:
+ - IOM manuals
+ - Commissioning report
+ - Warranty documentation
+ - Record drawings
+```
+
+## The Contractor shall submit the following informational submittals:
+
+- Manufacturer field service or startup report where factory commissioning is specified.
+- Operator training records, including attendance and topics covered.
+
+```datasheet
+label: Informational submittals required
+type: checkbox
+options:
+ - Field startup report
+ - Operator training records
+default:
+ - Field startup report
+ - Operator training records
+```
+
+# Quality Assurance {toc}
+
+## High-intensity luminous heaters shall be listed and labeled to ANSI Z83.19 / CSA 2.35.
+
+## Low-intensity radiant tube heaters shall be listed and labeled to ANSI Z83.20 / CSA 2.34.
+
+## The specifying engineer shall confirm whether the application is open or enclosed before selecting between high-intensity and low-intensity heaters.
+
+## The two product standards are not interchangeable; a contractor substitution across families changes the venting, ventilation, and clearance basis. {note}
+
+## Radiant performance shall be rated in accordance with ANSI/AHRI 1330-2024, and submitted data shall report the Radiant Emission Value (REV).
+
+## The 2024 edition of AHRI 1330 introduced the Radiant Emission Value as a directly comparable measure of usable radiant output, replacing older radiant efficiency fractions; specifying REV on submittals prevents substitution of a heater that meets the BTU input rating but delivers materially less radiant heat to occupant level. {note}
+
+## Each heater shall be the product of a single manufacturer for a given heater family on the project, to maintain consistency of parts, controls, and service support.
+
+## Manufacturer field service representatives performing startup shall be factory-trained and authorized for the supplied equipment.
+
+# Environmental and Service Conditions {toc}
+
+## Heaters shall be selected for the served space's ceiling height, infiltration, insulation level, door-cycle exposure, and occupant heat gain, not by a rule-of-thumb BTU per square foot value.
+
+## High-bay and dock-door-heavy facilities have infiltration and stratification behavior that rule-of-thumb area loads do not capture; a building heat-loss calculation is the basis of capacity and heater count, and skipping it produces undersized or oversized systems and uneven coverage. {note}
+
+## Tube material shall be selected for the corrosivity of the served environment.
+
+### Aluminized steel tube is the standard selection for dry, non-corrosive interior environments. {note}
+
+### Stainless steel tube shall be specified for combustion chambers and for installations exposed to washdown, salt, or chemical atmospheres.
+
+### Aluminized steel corrodes prematurely in washdown, salt, or chemical environments; stainless steel is required in those conditions. {note}
+
+### Titanium combustion-chamber tube may be specified for the most aggressive corrosive service where extended tube life justifies the cost. {note}
+
+```datasheet
+label: Tube material (low-intensity heaters)
+type: radio
+options:
+ - Aluminized steel (standard dry interior)
+ - Stainless steel combustion chamber
+ - Stainless steel full length (corrosive/washdown)
+ - Titanium combustion chamber (aggressive service)
+default: Aluminized steel (standard dry interior)
+```
+
+## In Seismic Design Category C and above, heater supports and bracing shall be designed in accordance with IBC Table 1613 seismic provisions.
+
+## Where heaters are suspended from a vibrating structure, vibration-isolation hangers shall be provided in accordance with NFPA 54.
+
+```datasheet
+label: Seismic bracing required
+type: radio
+options:
+ - Not required (SDC A or B)
+ - Required (SDC C and above)
+default: Not required (SDC A or B)
+```
+
+# Capacity and Performance {toc}
+
+## Each heater's input capacity shall be selected from the heat-loss calculation for the zone it serves.
+
+## Input capacity for a typical industrial low-intensity tube heater falls between 80,000 and 150,000 BTU/hr; the full covered range for the equipment family is 20,000 to 250,000 BTU/hr per unit. {note}
+
+```datasheet
+label: Rated input per heater
+type: range
+unit: BTU/hr
+min: 20000
+max: 250000
+step: 5000
+default: 125000
+```
+
+## High-intensity luminous heaters shall have a net radiant efficiency of not less than 55%.
+
+## Low-intensity radiant tube heaters shall have a net radiant efficiency of not less than 45%.
+
+## Net radiant efficiency is the fraction of fuel input emitted as usable infrared radiation toward the occupied zone; the minimum thresholds reflect the AHRI 1330 / NECB basis and are the floor below which a heater is not considered an efficient radiant emitter. {note}
+
+```datasheet
+label: Minimum net radiant efficiency
+type: range
+unit: '%'
+min: 45
+max: 75
+step: 1
+default: 50
+```
+
+## Steady-state thermal efficiency of the heater shall be not less than the minimum required by ASHRAE 90.1 where the project pursues energy code compliance.
+
+## Steady-state thermal efficiency for tube heaters typically ranges from 77% to 93% on a higher-heating-value basis; a standard tube heater is approximately 80% to 85%. {note}
+
+```datasheet
+label: Minimum steady-state thermal efficiency (HHV)
+type: range
+unit: '%'
+min: 77
+max: 93
+step: 1
+default: 82
+```
+
+# Heater Construction and Configuration {toc}
+
+## Low-intensity heater tube geometry shall be selected for the coverage pattern and the available run length of the zone.
+
+### Straight single-pass tube provides a linear coverage pattern along the run and suits long aisles and perimeter runs. {note}
+
+### U-tube geometry folds the run to fit a shorter footprint while retaining tube length, and suits bays where a straight run will not fit. {note}
+
+### Multi-burner continuous-tube systems provide a single continuous radiating run served by multiple burners for very long coverage, and suit large open floors. {note}
+
+```datasheet
+label: Tube geometry (low-intensity)
+type: radio
+options:
+ - Straight single-pass
+ - U-tube
+ - Multi-burner continuous tube
+default: U-tube
+```
+
+## Tube length shall be coordinated with mounting height per the manufacturer's layout guide so that the coverage pattern is uniform over the occupied zone.
+
+## A long tube hung at a low mounting height concentrates heat unevenly along the run; the tube-length-to-mounting-height ratio shall be evaluated against the manufacturer's layout guide rather than chosen by tube length alone. {note}
+
+## The 80% case is a 40 ft straight or U-tube heater; the practical range is 20 to 80 ft for single-burner straight tubes, with U-tubes giving an equivalent effective length of roughly 30 to 60 ft. {note}
+
+```datasheet
+label: Tube length (low-intensity)
+type: range
+unit: ft
+min: 10
+max: 80
+step: 5
+default: 40
+```
+
+## Tube diameter shall be 4 in. for standard industrial capacity ranges and may be 3 in. for lower-capacity units.
+
+```datasheet
+label: Tube diameter (low-intensity)
+type: radio
+options:
+ - 4 in. (standard industrial)
+ - 3 in. (lower capacity)
+default: 4 in. (standard industrial)
+```
+
+## Reflectors shall be provided over the full radiating length to direct radiant output downward toward the occupied zone.
+
+### Reflector finish shall be specified for the application; polished aluminum and polished stainless steel are the common finishes. {note}
+
+### A higher-reflectance, durable finish increases the fraction of radiant output directed to the floor and resists tarnishing in dusty or humid spaces. {note}
+
+```datasheet
+label: Reflector material and finish
+type: radio
+options:
+ - Polished aluminum
+ - Polished stainless steel
+default: Polished aluminum
+```
+
+## Reflector assemblies shall include the manufacturer's expansion provision to accommodate thermal movement of the tube.
+
+## Reflector expansion joints and burner-end baffles shall be verified against the IOM before energizing.
+
+## Omitting the reflector expansion joint, or installing the burner-end baffle in the wrong tube segment, are common installation errors that cause tube burn-through or poor heat distribution. {note}
+
+## The burner ignition system shall be direct spark ignition or hot surface ignition as scheduled.
+
+```datasheet
+label: Ignition type
+type: radio
+options:
+ - Direct spark ignition
+ - Hot surface ignition
+default: Direct spark ignition
+```
+
+# Mounting and Clearances {toc}
+
+## Each heater shall be mounted at the height and tilt angle shown on the heater layout plan [[drawing: heater mounting schedule]].
+
+## Mounting height for low-intensity tube heaters typically ranges from 10 to 35 ft, and for high-intensity luminous heaters from 8 to 20 ft; the 80% warehouse case mounts low-intensity heaters at 16 to 24 ft above finished floor. {note}
+
+```datasheet
+label: Mounting configuration
+type: radio
+options:
+ - Ceiling-mount (horizontal)
+ - Angle-mount (tilted)
+ - Wall-mount
+default: Ceiling-mount (horizontal)
+```
+
+```datasheet
+label: Mounting height above finished floor
+type: range
+unit: ft
+min: 8
+max: 35
+step: 1
+default: 20
+```
+
+## Clearances to combustibles shall comply with the listing label and the manufacturer's IOM for the specific model and mounting configuration.
+
+## Listed clearances for tube heaters are typically on the order of 48 to 84 in. above and 36 in. to the sides, but the listing label and IOM are the governing values for the supplied model and shall always be used in place of any generalized figure. {note}
+
+## The minimum mounting height and the maximum permitted combustible stacking height below each heater shall be shown on the layout plan and posted at the heaters.
+
+## NFPA 54 and NFPA 1 require posted signage for combustible clearances below radiant heaters; a specification that omits the minimum mounting height and maximum stacking height generates RFIs and fails code inspection. {note}
+
+## The heater layout shall account for line-of-sight obstructions such as high racking, overhead cranes, and mezzanines so that no occupied area is shadowed.
+
+## Radiant heat travels in straight lines, so tall racking can shadow lower zones; where obstructions block coverage, supplemental lower-mount or spot heaters shall be added to the layout rather than relying on the overhead heaters alone. {note}
+
+# Gas, Combustion Air, and Venting {toc}
+
+## Each heater's required gas inlet pressure shall be verified against the available supply pressure at the heater connection.
+
+## Natural gas heaters typically require 6 to 14 in. W.C. inlet pressure and propane heaters typically require 11 to 14 in. W.C.; these requirements shall be coordinated with the building regulator and meter set, because a low-pressure distribution system can fail to deliver the heater's minimum inlet pressure. {note}
+
+```datasheet
+label: Gas inlet pressure available at heater
+type: range
+unit: in. W.C.
+min: 5
+max: 14
+step: 0.5
+default: 7
+```
+
+## Combustion air shall be provided in accordance with NFPA 54, Section 9.3, for the volume of the space and the total connected input.
+
+## The combustion-air source shall be induced-draft, power-vented, or natural-draft as scheduled, and the flue shall be routed to the exterior.
+
+```datasheet
+label: Combustion air and draft configuration
+type: radio
+options:
+ - Induced-draft (vented)
+ - Power-vented (vented)
+ - Natural-draft (vented)
+ - Unvented (high-intensity)
+default: Induced-draft (vented)
+```
+
+## Vented heaters shall be vented as a Category I or Category II appliance per NFPA 54, Chapter 12, using Type B vent or single-wall metallic vent as listed for the model.
+
+## Where two or more tube heaters share a common vent, their controls shall be interlocked so the off-cycle unit cannot be back-fed by exhaust from the operating unit.
+
+## Common vents shared by two or more tube heaters shall be used only where the controls are interlocked so the off-cycle unit cannot receive back-fed exhaust from the operating unit.
+
+## Where interlocking common-vent controls is not feasible, individual vents shall be provided for each heater.
+
+## Common-venting tube heaters without interlocked controls drives exhaust from the operating unit down the flue of the off-cycle unit, causing premature heat exchanger failure and a carbon monoxide hazard. {note}
+
+## Unvented high-intensity heaters shall be installed only where mechanical ventilation provides at least 4 ft³/min per 1,000 BTU/hr of connected input, in accordance with NFPA 54.
+
+## Unvented luminous heaters shall not be specified in spaces with inadequate ventilation or with combustible storage directly below.
+
+## Unvented luminous heaters discharge combustion products into the space; specifying them where ventilation is inadequate or combustible storage is directly below creates both a fire code violation and a carbon monoxide hazard. {note}
+
+```datasheet
+label: Unvented ventilation rate (if unvented)
+type: range
+unit: CFM per 1000 BTU/hr
+min: 4
+max: 8
+step: 0.5
+default: 4
+```
+
+# Electrical {toc}
+
+## Electrical connection shall comply with NFPA 70 (NEC) Article 422 for appliances.
+
+## Heaters shall be supplied at 120V, single-phase, 60 Hz unless otherwise scheduled, with ignition and control current draw typically between 2 and 8 A.
+
+```datasheet
+label: Electrical supply
+type: radio
+options:
+ - 120V / 1Φ / 60 Hz
+ - 24V control (transformer-supplied)
+default: 120V / 1Φ / 60 Hz
+```
+
+## A disconnecting means shall be provided within sight of each heater, or lockable at the heater, in accordance with NEC Article 422.31.
+
+# Controls {toc}
+
+## The heater control strategy shall be selected for the zoning and turndown the space requires.
+
+### A single-stage thermostat zone is the simplest control and suits small or uniformly loaded spaces. {note}
+
+### Two-stage firing (typically 65% and 100%) reduces cycling and improves comfort in larger zones. {note}
+
+### Modulating control (typically 40% to 100% turndown) gives the smoothest output and the best part-load efficiency for large or variable loads. {note}
+
+```datasheet
+label: Control strategy
+type: radio
+options:
+ - Single-stage thermostat
+ - Two-stage (65% / 100%)
+ - Modulating (40-100%)
+default: Two-stage (65% / 100%)
+```
+
+## Where modulating or staged heaters are integrated with a building automation system, the interface protocol shall be confirmed with the BAS engineer before procurement.
+
+## Specifying modulating or staged controls without confirming the integration protocol with the building automation system results in standalone thermostats that cannot participate in demand-controlled heating; the protocol shall be coordinated with [[sync/building-automation-system]] before the heaters are released. {note}
+
+```datasheet
+label: BAS integration interface
+type: radio
+options:
+ - Standalone thermostat (no BAS)
+ - 0-10V analog
+ - BACnet MS/TP
+ - BACnet/IP
+default: Standalone thermostat (no BAS)
+```
+
+# Installation {toc}
+
+## Heaters shall be installed in accordance with the manufacturer's IOM, the listing label, NFPA 54, and the International Mechanical Code.
+
+## Heater hangers shall be supported from the building structure as detailed, and not from the bottom chords of open-web steel joists alone.
+
+## Hanger loads shall connect to joist panel points, bridging, or approved supplemental structural support, and shall not be applied to the joist bottom chord between panel points.
+
+## Hanger attachment locations shall be coordinated with the structural engineer.
+
+## Warehouse roofs are commonly open-web steel joists; applying hanger loads to the bottom chord between panel points can overstress the chord. {note}
+
+## Gas connections to each heater shall be made with a listed flexible connector and an accessible manual shutoff valve at the heater.
+
+## Final gas piping to the heater shall connect to the building gas distribution as covered by [[sync/natural-gas-piping]]; the connection point, regulator, and manifold pressure are coordinated there.
+
+## Vent terminations shall be located in accordance with NFPA 54 clearance-to-opening requirements and shall be coordinated with combustion-air intakes and supply-air openings served by [[sync/hvac-fans]].
+
+## Reflector segments, expansion joints, and burner-end baffles shall be installed in the positions and segments designated in the IOM, and verified before energizing.
+
+# Testing and Commissioning {toc}
+
+## Each heater shall be commissioned in accordance with the manufacturer's startup procedure.
+
+## Gas inlet pressure and manifold pressure shall be measured at each heater and confirmed to be within the manufacturer's required range under firing conditions.
+
+## Ignition shall be verified for reliable light-off, and staging or modulation shall be verified to track the control signal across the firing range.
+
+## Vented heaters shall be checked for proper draft and the absence of flue-gas spillage at the draft hood or barometric relief.
+
+## Unvented heaters shall be commissioned only after the required ventilation rate is confirmed to be operating.
+
+## A carbon monoxide spot check shall be performed in the occupied zone of spaces served by unvented heaters.
+
+## Commissioning results shall be recorded in the commissioning report submitted at closeout.
+
+# Delivery, Storage, and Handling {toc}
+
+## Heaters, tubes, reflectors, and controls shall be delivered in the manufacturer's original packaging with listing labels intact.
+
+## Tubes and reflectors shall be stored off the ground and protected from moisture, dust, and physical damage until installation.
+
+## Burner and control assemblies shall be kept dry and protected from construction debris until the heaters are energized.
+
+# Warranty {toc}
+
+## The manufacturer shall warrant heat exchangers, tubes, and burners against defects in materials and workmanship for not less than the period scheduled for the project.
+
+## The manufacturer shall warrant burner controls and ignition components for not less than the period scheduled for the project.
+
+```datasheet
+label: Heat exchanger / tube warranty period
+type: range
+unit: years
+min: 1
+max: 10
+step: 1
+default: 3
+```
+
+```datasheet
+label: Controls and burner warranty period
+type: range
+unit: years
+min: 1
+max: 5
+step: 1
+default: 1
+```
+
+# Spare Parts {toc}
+
+## The Contractor shall furnish the spare parts scheduled below, in the manufacturer's original packaging and labeled for the heater model they serve.
+
+- One spare ignition assembly (spark electrode or hot surface igniter) per heater model.
+- One spare gas valve per heater model.
+- One spare flame-sensing or safety control per heater model.
+
+```datasheet
+label: Spare parts furnished
+type: checkbox
+options:
+ - Ignition assembly (per model)
+ - Gas valve (per model)
+ - Flame-sense / safety control (per model)
+default:
+ - Ignition assembly (per model)
+ - Flame-sense / safety control (per model)
+```
+
+## This standard was independently authored by the SynC Standards Team from public consensus standards, building and fire codes, and general professional knowledge. It is licensed CC BY-SA. It does not reproduce any proprietary guide specification. {note}