Menu
Back to Blog
July 13, 2026TAB Testing

Do You Dalt?

By BalCon Team

Do You Dalt?

Do You Dalt?

July 13, 2026· BalCon Team

DALT stands for Duct Air Leakage Testing. Before the HVAC system is started, sections of ductwork are sealed off and filled with air. We measure how much air leaks out. If too much escapes, the leaks are sealed and the duct is tested again until it passes.

If needed, we can also perform a smoke test. Smoke is blown into the duct so leaks become visible, making them quick and easy to repair before ceilings are closed and equipment is started.

Why It Matters

Finding duct leaks before startup saves time, money, and headaches later.

For general contractors, DALT helps:

  • Catch installation issues before ceilings are closed.

  • Reduce punch list items and costly rework.

  • Keep commissioning and owner turnover on schedule.

  • Deliver a higher-quality project the first time.

For engineers, DALT confirms the installed ductwork performs the way it was designed and meets the project's leakage requirements.

For owners, tighter ductwork means lower energy bills, better airflow, and HVAC systems that operate more efficiently for years to come.

According to research for the U.S. Department of Energy, duct leakage is the largest source of energy waste in commercial buildings, costing an estimated $4 billion every year.

Meeting Code Requirements

Many projects require duct leakage testing to satisfy energy codes or project specifications.

Current ASHRAE 90.1 standards require much tighter duct systems than in the past, with Leakage Class 4 and Seal Class A.

Testing should always be completed before the ductwork is concealed. Repairing a leak before drywall is installed takes minutes. Finding that same leak after the building is finished can take days.

The Bottom Line

Performing Duct Air Leakage Testing before equipment startup and commissioning helps you verify ductwork is ready for the next phase of construction. When leaks are found, contractors can make repairs before startup, commissioning, and final owner turnover.

A few hours of testing today can prevent schedule delays, reduce rework, simplify commissioning, and eliminate years of wasted energy.

Back to Blog