Engineered Systems - February 2008 - (Page 48) Eight Ways To Keep Legionella Out This cooling tower (grate in foreground) is only a few feet away from the fresh air intake (background). AIR DISTRIBUTION SYSTEMS Air distribution systems can serve as a breeding ground and pathway for Legionella bacteria. The eight preventive measures that follow, some of which have been widely recommended for overall IAQ, will reduce Legionella risk. • Avoid cold-water humidifiers in ducts. If humidification is required, use steam humidifiers instead. Steam units are generally not conducive to Legionella because they operate at a temperature above which the bacteria can survive. In addition, they generate vapor rather than water droplets. Periodically descale steam humidifiers. If scaling is rapid, consider supplying the units with softened water to reduce the rate. Drain the humidifiers when not in use. If cold-water humidifiers cannot be eliminated, provide them with a domestic water source and drain line instead of using recirculated water. The supply water should ideally be at 68°F (20°C) or below. Keep all humidifiers leak-free and clean. • Keep ducts dry. Design ducts so that water from condensation or other sources does not accumulate. Drain lines should include a trap and air break so that contaminated water is not drawn back into the system. Fix pipe leaks. Legionella-contaminated water leaking from pipes can enter ducts and become aerosolized and distributed to occupied spaces. It is especially important to find and fix leaks in systems (e.g., fire sprinkler systems) that may harbor stagnant water. In the vicinity of humidifier installations, check ductwork periodically for evidence of condensate pooling. In some cases, moisture from humidifiers pools downstream in the duct. • Make sure that condensate drain pans drain well and are kept clean. Clean the pans with a biocide at least twice a year — preferably once a quarter — to remove all slime and dirt (little should accumulate if the pans drain properly). Replace drain pans that are The PLATINUM Standard for Humidifiers Adiabatic Humidifiers High Pressure Water Atomizing Humidifier Air/Water Atomizing Humidifier Isothermic Humidifiers Electrode Steam Humidifier Electric Element Steam Humidifier Centrifugal Atomizing Humidifier Gas Fired Steam Humidifier Direct Injection Steam Humidifier humidification for life CAREL USA 385 S. Oak Street - Manheim, PA 17545 - Phone 717.664.0500 - Fax 717.664.0449 - email: sales@carelusa.com www.carelusa.com FREE INFO: 117 48 ESM11074Carel.indd ESM02084Carel.indd 1 1 En gi neer ed S y stem s February 2008 10/11/07 11:24:46 AM 1/14/08 9:47:46 AM http://www.carelusa.com http://www.carelusa.com
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