What is a Low Nox Furnace in Colorado?

by | Apr 21, 2026

In Colorado, a Low NOx furnace is a specialized heating system engineered to minimize nitrogen oxide (NOx) emissions, which helps protect air quality in the state’s high-altitude environment. These systems are designed to reduce emissions below 40 nanograms per joule (ng/J). Due to strict ultra-low NOx regulations implemented by the Colorado Department of Public Health and Environment, many areas—particularly along the Front Range and Denver metro—now require furnaces to meet an even lower emission limit of 14 ng/J or less.

These furnaces are particularly important in Colorado for several reasons:

Compliance and Regulations: Since 2015, the state has enforced stringent air quality standards for new or replacement units in populated regions like Denver, Aurora, and Colorado Springs.

High-Altitude Performance: Models such as the Trane XC95M and Compact A801X are specifically engineered to provide reliable heating at elevations above 5,000 feet, where thinner air can often lead to incomplete combustion.

Efficiency and Savings: These units often feature high-efficiency ratings up to 96% to 98% AFUE. They frequently qualify for ENERGY STAR certification and local rebates, such as those from Xcel Energy, which can offer up to $500 for qualifying upgrades.

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