🌫️ What the Heck Is “NOx,” Anyway?
Mike here.
If you're shopping for a new furnace and keep seeing “Low NOx” or “ULN,” you’re probably wondering, “Do I need this? And what does it even mean?”
NOx stands for nitrogen oxides—pollutants released during combustion. They’re a major contributor to smog and respiratory problems, which is why certain states—especially California—have strict emission standards for residential furnaces.
If your furnace doesn’t meet Low NOx or Ultra-Low NOx specs, you might not even be allowed to install it in some ZIP codes.
Learn more at South Coast AQMD’s Residential Furnace Rule 1111
🏷️ What’s the Difference Between Standard, Low NOx, and Ultra-Low NOx?
| Type | NOx Emissions (grams/hour) | Where It's Allowed |
|---|---|---|
| Standard Furnace | ~40 | Most states |
| Low NOx Furnace | ~14 | CA, parts of TX |
| Ultra-Low NOx | ~9 or less | Southern CA & strict districts |
🛠️ How Do Low NOx Furnaces Work?
Low NOx and ULN models tweak how the burners mix fuel and air, and often add special premix burners to reduce flame temperature and NOx output.
The best part? With newer R-32 gas furnaces, this tech is baked in without sacrificing heat output or efficiency.
For a deep dive on this tech, check out Contracting Business’s Low NOx Furnace Overview
💨 Why R-32 Gas Furnaces Are a Smart Choice for Low NOx Zones
Here’s why I recommend R-32 gas furnaces if you’re in a NOx-restricted area:
✅ 1. Built-in Compliance
Most R-32 models from brands like Goodman and Amana are already Low NOx certified, and many are ULN ready. That means no worrying about code violations or retrofit kits.
✅ 2. Efficient Combustion
R-32-compatible furnaces are designed with tight burner tolerances and optimized airflow, which naturally lowers flame temp and emissions.
✅ 3. Easy Pairing with Low NOx AC Units
If you’re installing a full heating and cooling system, your outdoor unit may also need to be low NOx or low GWP. R-32 handles both.
For more on pairing systems in emission-restricted areas, EnergyStar has a good overview:
Read: ENERGY STAR Regional Standards and Regulations
🧊 Bonus: California Rebates for Low NOx Systems
California and other green energy states often offer cash rebates for installing a ULN gas furnace—especially when it’s paired with a high-efficiency R-32 AC unit.
Visit the Go Green California Rebate Finder to see what’s available in your area.
🔍 Mike’s Top Picks for Low NOx R-32 Furnaces
🌟 Goodman GR9T961005CN (96% AFUE, 100K BTU)
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Two-stage heating with quiet variable-speed blower
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Low NOx certified
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Excellent for homes 2,000–2,800 sq. ft.
🌟 Amana Distinctions ULN Furnace – 80K BTU
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Great for West Coast customers
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Matches with ULN outdoor R-32 AC units
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Simple diagnostics = fewer service calls
✅ Final Word from Mike
Look—if you’re in a NOx-regulated area, you can’t afford to guess. You need a furnace that’s compliant out of the box.
The good news? R-32 gas furnaces are ready to go—with the emissions reductions, the rebates, and the comfort.
If you're not sure which models are ULN or Low NOx approved in your state, just drop us a message at The Furnace Outlet. I’ll help you get the right furnace without the fine print.
Stay legal, stay warm,
– Mike
In the next topic read about: What Size Gas Furnace Do I Need? Mike Breaks Down BTUs, Square Footage & R-32 Efficiency
