MLR series semi-custom air handling units are an economical alternative to fully custom AHUs, while still having a wide range of component and design options and including the benefits of being modular and knock-downable.

MLR units are Flat-Pak certified!

Give us a call to find out about getting a unit delivered broken down on pallets, ready for site assembly.


  • Double-wall panels, 2” thick, with basic thermal break design and injected polyurethane foam insulation
  • Indoor or outdoor designs, variable width and height
  • Extensive range of available components, including humidifiers, energy recovery, HEPA filters, etc.
  • Removable panels


  • Full access for servicing components
  • Minimal disruption to existing ductwork and piping, thanks to the ability to match an existing footprint
  • Ease of installation; sections can be made small enough to fit through doorways, etc.
  • Minimal infiltration, exfiltration and radiant heat conduction mean impressive energy savings

We typically include EC Fan Arrays in MLR units.

If there is anyone you would like me to direct some positive feedback to, I'd be happy to do it. It's been a long time since I've experienced service like the entire Mainstream team provided on this order.

Trotter & MortonGeneral Manager

I have found Mainstream equipment built to a very high standard to deal with our demanding applications, while being competitive in pricing. Their sales and engineering staff have been responsive and helpful in making equipment selections and offering solutions to difficult projects.

Cold Spring Harbor LaboratoriesAssistant Director of Facilities

If you utilize them, you won't be disappointed, great communication, good customer service, very good product.

Lackland Air Force BaseHVAC Systems Supervisor

Learn about our MLRa Series Fully Custom Air Handling Units