Germicidal UV (UVC) lamps have a long history of use for inactivation of microbial aerosols. The majority of the literature has considered control of infectious diseases, such as tuberculosis (TB) in medical facilities. Emphasis has recently been on ventilation duct use of UVC. Under these conditions, infections agents are usually of less concern than environmental organisms. Much less information is available regarding common environmental organisms. The present work reports the ability of UVC lamps to inactivate 7 representative microbial aerosols in ventilation duct conditions.
Published guidelines on mold remediation do not specify sampling protocols to measure the efficacy of remediation efforts. The purpose of this study was to evaluate fungal remediation of contaminated ducts by comparing the amount of residual surface contamination to the amount in new ducts. Fungal contamination of galvanized metal and rigid fibrous glass ducts were evaluated using fluorometric and microscopic methods. Fungal contamination was measured in newly installed ducts in addition to pre- and post-remediation. Newly installed ducts had low levels of fungal debris.
The velocity field in circular ducts has been measured downstream 8 representative disturbances (elbows, junctions, damper, ...). The uncertainty in flow rate calculation has been defined.
Fiberglass duct interior liners with and without biocides were submitted in an environmental chamber during 15 days to high air humidities, moisture and nutrient. Conclusion is that liners with biocide reduce microbial growth under high humidity as long as they remain dirt free and dry. Impermeable smooth liners show better performance than liners with porous or rough surface.
The demand for duct cleaning has been increasing exponentially over the last few years and to determine objectively if the duct is dirty and has to be cleaned is necessary.All air-handling units from a school district (18 buildings) and representative portions of their associated ductwork were assessed. Results of dirt and contamination are compared to dirt criterias and commented.
In the context of the definition of new national ventilation cleanliness classes in Finland, it is important to develop a clean method for the installation of ducts. An important factor that makes the inner duct surfaces dirty is the metal dust that is accumulated while side grinder is used to cut the ducts.
The aim of this study was to evaluate the amount of dust in supply air ducts in 18 recently installed ventilation systems constructed according to two different class of cleanliness. Dust accumulation into the duct can be partly avoided by duct protection during the whole of the construction phase.
Maintenance is often limited to repair and failure response and not dedicated to indoor environment. The study defines levels of cleanliness depending on the method of measurement and compares surface values on the components to air pollution in order to decide if guidelines with limit values for surfaces are sufficient.
Labelling of HVAC systems is a direct consequence of the publication of test procedures and recommended criteria in Finland. Cleanliness parameters are dust quantity, oil residues and odours emissions. Discussion isf continuing on filters classification including their efficiency (EN 779) but also odour emissions.
Two models were applied to predict particle deposition in ducts, one theoretical, the other based on experiments. These models are described and a comparison of their predictions is compared to experimental results.
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