NAFA Certified Air Filter Specialist (CAFS) Practice Exam 2025 – Your Comprehensive Guide to Certification Success!

Testing HEPA filters after installation is referred to as in-place leak testing or the cold DOP test. This practice is crucial because it ensures that the filter is functioning correctly and is free from leaks that could allow unfiltered air to bypass the filter. During this process, a challenge aerosol (typically di-octyl phthalate, or DOP) is introduced to the filter. The integrity of the HEPA filter is assessed by measuring the amount of aerosol that passes through it compared to what is introduced. A successful test indicates that the filter meets the required specifications for air cleanliness and is providing adequate protection against particulate contamination.

This testing is preferred because it simulates actual operating conditions, thereby providing a realistic assessment of the filter's performance in situ. Other types of inspections or tests, such as routine maintenance checks or preliminary inspections, may be important but do not serve the specific purpose of confirming the effectiveness of the HEPA filter post-installation. Standard operational testing, while relevant, does not distinctly address the need to verify the integrity of the filter using the procedures and methodologies specific to in-place or cold DOP tests.