NADCA Vacuum Testing Procedure
The NADCA vacuum test, developed by the National Air Duct Cleaners Association (NADCA), is a standardized method used to evaluate the cleanliness of HVAC ductwork following mechanical cleaning. Introduced as part of NADCA’s ACR Standard, the test provides a quantifiable way to measure residual debris by vacuuming a defined area of duct surface through a pre-weighed filter cassette. After collecting a sample, the filter is re-weighed in a laboratory to determine the amount of particulate removed. The result, expressed in milligrams per 100 cm², is compared to a pass/fail threshold of 0.75 mg/100 cm². The test is widely used in commercial and industrial HVAC cleaning projects to verify cleaning effectiveness, support IAQ compliance, and fulfill post-cleaning verification requirements.
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In most cases, the testing requirements, sampling locations, and responsibility for conducting the NADCA vacuum test—whether assigned to the contractor or the owner—are outlined in the project specifications section of the contract documents.
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​If testing is required, the steps outlined below provide a clear, step-by-step guide to the complete testing process:
Step One
Locate the testing area(s): Testing must be completed shortly after cleaning before the HVAC system is turned back on. The template must be taped down to a flat horizontal duct section roughly one square foot in size.
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Step Two
Gather testing materials: Purchase a filter from our shop. The filter is pre-weighed at our lab and comes with a sampling form, and a prepaid return envelope. Ensure you have purchased or obtained a template, and a vacuum pump calibrated to 10 liters per minute flow rate.
Step Three
Clean the Duct: Clean the ductwork to the specified level of clean, using the methods detailed in the spec section.
Step Four
Collect the sample: Adhere the template to the designated sampling location with some tape. Remove the filter from the bag, remove the nozzle stops on either side, and attach it to the pump tubing. Make sure that a pair of powder free gloves is worn when handling the cartridge. The oils and dirt on your hands can affect the weight of the sample. Turn on the pump and use the cartridge to vacuum the sample area in slow passes for 5 minutes and 36 seconds. Turn off the vacuum pump, remove the filter cartridge, replace the nozzle stops, and place it back in the bag.
Step Five
Complete the paperwork: Fill out the sampling paperwork that comes with the filter. Place the bagged filter, and the paperwork into the prepaid envelope and mail it back to our lab.
Step Six
Labwork: The lab will process your sample and provide you will pass/fail paperwork via email and text within 24 hours of receiving the sample.