Madison Air designs, manufactures, and distributes indoor air quality (IAQ) products and systems for commercial and residential customers across North America. The company operates through two segments: Commercial (~66% of net sales) and Residential (~34%). On the commercial side, Madison Air sells custom and semi-custom engineered air handling and cooling systems to mission-critical environments including data centers, hospitals, semiconductor cleanrooms, and industrial facilities — markets where poor air quality carries measurable, high-cost consequences. The company engages directly with hyperscalers and colocators on data center cooling, where its commercial backlog grew to ~$2B as of year-end 2025. On the residential side, Madison Air sells whole-home air quality solutions — including purification, humidification, dehumidification, and ventilation — primarily under the AprilAire and Broan-NuTone brands, through wholesale distributors and dealers. Roughly 70% of residential net sales come from replacement and upgrade demand. Aftermarket revenue (~10% of net sales) is a growing component of the model; proprietary replacement parts and service contracts can return multiples of the initial equipment sale over a product's lifecycle. Madison Air was built largely through acquisitions — most notably the Nortek acquisition in 2021 and the $2.6B AprilAire acquisition in 2025. Key brands include Nortek Air Solutions, Nortek Data Center Cooling, Big Ass Fans, Reznor, AprilAire, and Broan-NuTone. The company targets capital expenditures at 2% or less of net sales and prioritizes free cash flow conversion above 100%.