Study On Methods And Efficacy Of Air Disinfection In HVAC Systems

[Objective] Before severe acute respiratory syndrome (SARS) occurring, the disinfection of circular air used to be neglected in heating, ventilation and air conditioning (HVAC) systems in China. After this, scholars have been paying close attention to this problem. Now, we still starve for the rapid, efficient, safe, non-contaminative, dynamic, continuous, thrifty and practical methods. For finding out the methods which accord with this and have a steady and dependable disinfection result from air disinfection methods to make a guidance for people, we studied the methods of air disinfection and observed the air disinfection efficacy of high efficiency particulate air (HEPA), laser irradiation, electrostatic precipitation, ultraviolet germicidal irradiation (UVGI) and ozone disinfection on a proving ground in HVAC systems, and pointed out the setting sites and methods of these disinfection appliance, the valid disinfectant dosage, the merit and defect of these methods etc.[Methods] We chose one quality appliance on one kind of disinfection method to test according as the facts, cooperating with the disinfector manufacturers, and observed the air disinfection efficacy of these on a proving ground.Two methods were adopted in accordance with the 2. 1. 3. 5 item of Technical Standard for Disinfection (2002 edition). They were "the air disinfection qualification test of disinfecting for a period" and "the air disinfection efficacy qualification test of the air having passed through once".By this we categorized towards the disinfection methods finded out, and put forward guiding opinion, so as to choose for the HVAC designers.The air disinfection efficacy qualification test of disinfecting for a period. None indoor, we tested in a representative room according to the actual circumstance. The sampler being placed 1. Om high in the center of the room, we sampled the air in Andersen Microbil Sampler of 6 grades before and after disinfection. Then put both the sampling plate and the negative control plate in 37°C incubator in 48 hours for 3 times, and' calculated the decay rate of air natural bacteria.The air disinfection efficacy qualification test of the air having passed through once, putting two Andersen Microbil Sampler into the central position of incoming and outgoing vents, synchronously sampled the two vents after the appliance running 5 minutes, the rest steps were the same as before.[Main Results] The average decay rates of the natural bacteria are 95.85%, 90.4% and 62.85% with the methods of laser irradiation , HEPA and electrostatic precipitation after the air has passed through once. The rates of UVGI, ozone and UVGI combining with ozone are 97. 97%, 92. 31% and 94. 87% disinfecting for a period.[Conclusions] According to these results, we can rank these methods to 3 layers. The First, the average decay rate of natural bacteria is more than 90% after the air have passed through once, including laser irradiation and HEPA. The second,the rate is above 90% after the disinfection system running for a period, such as electrostatic precipitation and UVGI. The third are ozone and other chemical disinfection methods, and those which attain the lowest hygienic standards. And have pointed out the setting sites and methods of these disinfection appliance, the valid disinfectant dosage, the merit and defect of these methods etc. put forward guiding opinion, so as to choose for the HVAC designers.