Comprehensive analysis of fan configuration modes in the ventilation system of high-level biosafety facilities
The frequent occurrence of infectious diseases such as the novel coronavirus and SARS-CoV-2 has seriously affected human health and the social economy.Numerous high-level biosafety facilities,including high-level biosafety laboratories and risk workshops,have been developed worldwide to deal with highly pathogenic microbes and provide a relatively safe experimental environment.However,accidents involving laboratory-acquired infections are often reported due to the lack of protective technology and awareness during experimental procedures.This situation necessitates the implementation of a set of standard operating procedures,usage of personal and collective protective equipment,and development of engineering controls to prevent personnel from being exposed to potential infectious doses.One of the main features of engineering controls is related to the ventilation system,with ventilation fans(e.g.,supply and exhaust fans)as the key equipment.Supply fans are used to provide make-up air to offset exhaust and ventilation air for dilution control and room pressurization,while exhaust fans are used to meet the exhaust demand of collective protective equipment(e.g.,biological safety cabinets and individually ventilated cages)and laboratory ventilation requirements.The core measure for the safety of biosafety facilities is to maintain negative pressure through the ventilation system.Ventilation fans are the key equipment used to ensure the safety of high-level biosafety facilities.Some important issues,including their selection calculations,redundant backup configurations,operation modes,and automatic control schemes,have attracted increasing attention from designers.Relevant domestic and international norms,standards,and guidelines have proposed clear requirements for ventilation-fan configurations.On the basis of comparing these requirements combined with actual engineering examples,herein,a comprehensive analysis is conducted on the ventilation-fan configuration,including fan operation modes,mutual backup of multiple fans,variable frequency control,and fan selection in high-altitude areas.Ventilation-fan configurations should be determined based on risk assessment.Each ventilation and air conditioning system should be equipped with two independent supply fans(one for use and another for backup)and two exhaust fans(one for use and another for backup);this is the best engineering choice.Due to the many factors affecting pressure fluctuations in high-level biosafety facilities,fan-frequency conversion control is considered one of the most effective pressure gradient controls and energy-saving operation measures for high-level biosafety facilities.When selecting ventilation fans for high-level biosafety facilities,the total pressure of ventilation fans should be revised according to the ambient atmospheric pressure,considering the differences in air density in areas with different altitudes.This research provides suggestions for the future construction and development directions and promotion of high-level biosafety facilities in China.
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