Truestar Air Systems


An HVAC leakage testing machine, often referred to as a duct leakage tester, is a specialized piece of equipment used to measure the airtightness of heating, ventilation, and air conditioning (HVAC) ductwork systems. Here’s a comprehensive overview:

Purpose and Importance

1. Efficiency: HVAC systems rely on airtight ducts to efficiently deliver conditioned air. Leaks can result in significant energy losses, leading to higher utility bills and increased wear on the HVAC system.

2. Indoor Air Quality: Leaks can allow contaminants, dust, and allergens to enter the duct system, compromising indoor air quality.

3. Compliance: Many building codes and standards require duct leakage testing to ensure compliance with energy efficiency standards.


1. Blower/Fan Assembly: This generates the airflow needed to pressurize or depressurize the duct system.

2. Pressure Gauge/Manometer: This measures the pressure difference between the inside and outside of the duct system.

3. Flow Meter: This measures the volume of air being moved through the system, which helps in calculating leakage rates.

4. Sealing Components: Includes duct plugs, caps, and other materials to seal off portions of the duct system during testing.

5. Control Panel: Provides the interface for operating the machine, setting test parameters, and reading results.

Types of Testing

1. Positive Pressure Testing: The blower/fan assembly pushes air into the duct system to create a positive pressure, and the amount of air needed to maintain this pressure is measured.

2. Negative Pressure Testing: The blower/fan assembly draws air out of the duct system to create a negative pressure, and the amount of air removed to maintain this pressure is measured.

Testing Procedure

  1. Preparation:
  • Seal all vents and openings in the duct system except for the location where the tester is connected.
  • Ensure the HVAC system is turned off.
  1. Connection:
  • Attach the blower/fan assembly to a duct opening, typically at the air handler or main supply trunk.
  1. Pressurization/Depressurization:
  • Operate the blower/fan to either pressurize or depressurize the duct system to a specified test pressure (often 25 or 50 Pascals).
  1. Measurement:
  • Use the pressure gauge/manometer and flow meter to measure the pressure difference and the airflow required to maintain it.
  1. Calculation:
  • The leakage rate is calculated based on the airflow measurement at the specified pressure. This is usually expressed in cubic feet per minute (CFM) at a particular pressure.

Standards and Compliance

  • ASHRAE Standards: The American Society of Heating, Refrigerating and Air-Conditioning Engineers provides guidelines for duct leakage testing, such as ASHRAE Standard 152.

  • SMACNA Standards: The Sheet Metal and Air Conditioning Contractors’ National Association offers standards for duct construction and testing.

  • Energy Codes: Many regions require duct leakage testing to comply with energy efficiency codes, such as the International Energy Conservation Code (IECC).


  • Residential: Testing the ductwork in homes to ensure energy efficiency and compliance with building codes.
  • Commercial: Testing larger HVAC systems in commercial buildings, often with more stringent requirements.
  • Industrial: Ensuring the airtightness of duct systems in industrial settings, which may involve more complex systems and higher pressures.


  • Energy Savings: Reducing leakage can significantly lower energy consumption.
  • Improved Comfort: Ensuring proper air distribution enhances indoor comfort.
  • Enhanced Air Quality: Preventing contaminants from entering the duct system improves indoor air quality.
  • Cost-Effective: Identifying and sealing leaks can reduce the need for oversized HVAC equipment and lower maintenance costs.

Leading Manufacturers

Several companies manufacture HVAC leakage testing machines, each offering various models suited to different applications and testing requirements. Some well-known manufacturers include:

  • Retrotec
  • Duct Blaster
  • TSI/Airflow Instruments
  • Energy Conservatory (Minneapolis Blower Door)