Building vibration control for high plume exhaust fans

摘要

High plume dilution blowers for laboratory exhaust are commonly installed with fans and motors mounted on top of a sheet metal bypass air plenum, often without effective vibration isolation from the building structure. If the fans and motors are properly balanced, fan vibration transmitted to the building structure generally can achieve allowable tolerances for non-sensitive building spaces but can still exceed tolerances for sensitive laboratory uses. If exhaust ducts and roof penetrations are designed with passive measures to reduce fan noise transmission, and if the fan and plenum system is installed with high-deflection vibration isolation mounts to control structure-borne vibration transmission, high plume fan and plenum systems can be installed directly above sensitive laboratory spaces, achieving standard noise and vibration criteria for laboratories and lab instruments. This paper presents field-tested sound and vibration data from two laboratory facilities for forensic sciences and biological research with high plume blowers installed on the roof directly above sensitive spaces. Comparative charts of noise and vibration levels will be presented to show criteria and facility performance before and after building vibration corrections, along with diagrams and graphical illustrations of passive vibration and noise control measures.