However,in order to disarm any possible alarmistarguments,itis worth remembering thataccording to a study carried outby Health Building International on a total of 11million square meters of ductwork,only 10%ofoccupants’complaints concerning inadequate indoor air quality were due to contamination inside ducts.
Causes of discomforton HBI Study,IAQ •Maintenance operations:76% •Inefficientfiltration:56% •Low levels of ventilation:54% •Inadequate air distribution:21% •Pollution inside the ducts:12%
Nevertheless,itis obvious thatductnetwork has to be designed with the prospectof being cleaned during its future operational life.
Initial cleaning ofducts should be done beforethe installation is made operational.During operation, in addition to suitably adapted air replenishment, it is necessary to have efficient filters and to undertakecleaning and proper maintenance of the installation.
7.2Ductcleaning
This section is based on “Recommended BestPractices for inspection,opening,cleaning and closing of air ducts”,edited by the North American Insulation Manufacturers Association (NAIMA). The process of cleaning air ducts is divided into:
•Inspection and evaluation of the HVAC system as to whether itis necessary to clean the ducts or not,and if necessary,the measures needing implementation. •opening ducts •cleaning methods •closing of ducts after cleaning,final inspection and starting
a) Installation inspection Cleaning a duct network can be expensive and ineffective in providing a solution to problematic indoor air quality if the cause of the contamination cannotbe identified.For this reason,all potential causes ofthe problem should be fully explored before embarking on ductcleaning.
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