Manufacturers, specifiers, and users of gas phase (chemical) filtration have historically lacked an effective standard method to test, evaluate and compare gaseous filtration equipment. Industry groups, such as ASHRAE, are making progress in developing consensus standards for evaluating gas phase sorption equipment. The emphasis of these efforts has been on laboratory or test tube scale to evaluate sorption media and not on the full sized filters as fabricated and applied in HVAC systems. This paper describes the modifications made to a test duct manufactured to the specification of ASHRAE Standard 52.2. This test duct was developed to perform efficiency evaluation on full sized manufactured particulate filters at typical installed duct velocities. Adaptations were made to enable this industry consensus developed test duct to also perform full-scale efficiency testing on gas-phase filters as well. The modifications include reconfiguring the duct to a single pass air flow system, developing an apparatus for the introduction of additional humidity to the air flow, addition of apparatus for the introduction of multiple challenge gases at controlled concentrations, fabrication and installation of sampling manifolds to assure uniform sample acquisition, and design and fabrication of bracketing to seal sample filters in the test duct. The modified test duct was successfully demonstrated by evaluating a series of manufactured filters for comparison of efficiency performance. The demonstration established a common testing protocol using multiple test gases at low concentrations. Quality control data documented the diffusion effectiveness of the challenge gas introduction technique and the uniform airflow achieved by the test duct. The paper presents typical test results from the compared filters that demonstrate the usefulness of the testing apparatus and methodology in product characterization and selection.
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