Duct leakage testing pressurizes a duct system to a defined test pressure and measures airflow needed to maintain it. The result is meaningful only when test boundaries, equipment, floor area, and leakage type are documented. Use it with the Ductwork Guide when you need the broader system context.
Quick Decision Guide
| Decision area | What to verify | Common mistake |
|---|---|---|
| Total Leakage and Leakage to Outdoors | Document the existing condition and collect measurements specifically relevant to Total Leakage and Leakage to Outdoors before selecting equipment or approving work. | Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. |
| Prepare the System | Document the existing condition and collect measurements specifically relevant to Prepare the System before selecting equipment or approving work. | Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. |
| Understand CFM25 Results | Document the existing condition and collect measurements specifically relevant to Understand CFM25 Results before selecting equipment or approving work. | Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. |
| Find and Seal Defects | Document the existing condition and collect measurements specifically relevant to Find and Seal Defects before selecting equipment or approving work. | Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. |
| Verify After Repair | Document the existing condition and collect measurements specifically relevant to Verify After Repair before selecting equipment or approving work. | Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. |
Total Leakage and Leakage to Outdoors
Different test configurations answer whether air leaves the ducts and whether it crosses the building enclosure. Document the existing condition and collect measurements specifically relevant to Total Leakage and Leakage to Outdoors before selecting equipment or approving work. The useful question is not whether one feature sounds better in isolation, but how the proposed choice changes safety, capacity, airflow, comfort, operating cost, maintenance, and the rest of the installed system.
Use the documented conditions to compare compatible options, complete scope, and a measurable final result. Record the starting condition, model numbers, settings, measurements, assumptions, and expected result so a proposal can be verified after the work. Compare information at the same indoor and outdoor conditions whenever performance changes with weather or airflow.
Important limit: Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. Stop and use a qualified professional whenever the decision involves energized equipment, fuel, combustion, refrigerant, structural work, hazardous materials, permits, or a condition you cannot evaluate safely.
Prepare the System
Registers, equipment openings, intentional outdoor-air paths, and test connections must follow the chosen protocol. Document the existing condition and collect measurements specifically relevant to Prepare the System before selecting equipment or approving work. The useful question is not whether one feature sounds better in isolation, but how the proposed choice changes safety, capacity, airflow, comfort, operating cost, maintenance, and the rest of the installed system.
Use the documented conditions to compare compatible options, complete scope, and a measurable final result. Record the starting condition, model numbers, settings, measurements, assumptions, and expected result so a proposal can be verified after the work. Compare information at the same indoor and outdoor conditions whenever performance changes with weather or airflow.
Important limit: Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. Stop and use a qualified professional whenever the decision involves energized equipment, fuel, combustion, refrigerant, structural work, hazardous materials, permits, or a condition you cannot evaluate safely.
Understand CFM25 Results
Measured airflow at 25 pascals is commonly normalized to floor area or an applicable program threshold. Document the existing condition and collect measurements specifically relevant to Understand CFM25 Results before selecting equipment or approving work. The useful question is not whether one feature sounds better in isolation, but how the proposed choice changes safety, capacity, airflow, comfort, operating cost, maintenance, and the rest of the installed system.
Use the documented conditions to compare compatible options, complete scope, and a measurable final result. Record the starting condition, model numbers, settings, measurements, assumptions, and expected result so a proposal can be verified after the work. Compare information at the same indoor and outdoor conditions whenever performance changes with weather or airflow.
Important limit: Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. Stop and use a qualified professional whenever the decision involves energized equipment, fuel, combustion, refrigerant, structural work, hazardous materials, permits, or a condition you cannot evaluate safely.
Find and Seal Defects
Testing can be paired with pressure pan, smoke, visual, or diagnostic methods to locate important leaks. Document the existing condition and collect measurements specifically relevant to Find and Seal Defects before selecting equipment or approving work. The useful question is not whether one feature sounds better in isolation, but how the proposed choice changes safety, capacity, airflow, comfort, operating cost, maintenance, and the rest of the installed system.
Use the documented conditions to compare compatible options, complete scope, and a measurable final result. Record the starting condition, model numbers, settings, measurements, assumptions, and expected result so a proposal can be verified after the work. Compare information at the same indoor and outdoor conditions whenever performance changes with weather or airflow.
Important limit: Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. Stop and use a qualified professional whenever the decision involves energized equipment, fuel, combustion, refrigerant, structural work, hazardous materials, permits, or a condition you cannot evaluate safely.
Verify After Repair
Repeat the same test configuration and retain before-and-after results, photographs, and repaired scope. Document the existing condition and collect measurements specifically relevant to Verify After Repair before selecting equipment or approving work. The useful question is not whether one feature sounds better in isolation, but how the proposed choice changes safety, capacity, airflow, comfort, operating cost, maintenance, and the rest of the installed system.
Use the documented conditions to compare compatible options, complete scope, and a measurable final result. Record the starting condition, model numbers, settings, measurements, assumptions, and expected result so a proposal can be verified after the work. Compare information at the same indoor and outdoor conditions whenever performance changes with weather or airflow.
Important limit: Do not treat a product label, rule of thumb, or one unverified reading as a substitute for project-specific diagnosis. Stop and use a qualified professional whenever the decision involves energized equipment, fuel, combustion, refrigerant, structural work, hazardous materials, permits, or a condition you cannot evaluate safely.
Homeowner Checklist
- Write down the problem, affected rooms, timing, weather, and recent changes.
- Record equipment model numbers, age, controls, filters, service history, and known modifications.
- Ask which measurements and calculations support the recommendation.
- Compare exact models, complete scope, permits, commissioning, exclusions, warranties, and maintenance.
- Verify compatibility and current instructions with the manufacturer and responsible local authority.
- Keep the final settings, test results, manuals, invoices, and photographs with the home records.
Frequently Asked Questions
What should I check first? Document the existing condition and collect measurements specifically relevant to Total Leakage and Leakage to Outdoors before selecting equipment or approving work. Can one specification answer the whole question? No. Ratings and features must be interpreted with the home, installed equipment, distribution, controls, climate, and operating conditions.
When should I call a professional? Use qualified help for unsafe conditions, internal electrical or fuel work, refrigerant, permits, or when measurements are required. How should I compare quotes? Use the documented conditions to compare compatible options, complete scope, and a measurable final result. Compare the same scope and acceptance tests, not only price.
