title: [Microenvironment of positive pressure powered air purifying medical protective equipment].
abstract: OBJECTIVE
  To study the filtration efficiency of a positive pressure powered air purifying medical protective equipment and the effect of the flow rate on the microenvironment of the equipment.
  
  
  METHODS
  The filtration efficiency of high efficiency particulate air (HEPA) filter was measured with the biologic aerosol of simulating virus (Escherichia coli bacteriophage f(2)). The simulation work was done at the walk rate of 4 km/h in summer. The effect of the flow rate on the oxygen content, the carbon dioxide content, the temperature and the humidity of the microenvironment of the equipment was investigated. The clinical experiments were conducted in three appointed hospital for fighting against SARS.
  
  
  RESULTS
  The HEPA filter could filtrate 99.99% simulating viruses in the air. When the flow rate ranged from 75 to 125 L/min, the microenvironment parameters of the equipment were: the oxygen content was between 19.6% and 20.1% (the physiological safety limit is more than 14.6%); the carbon dioxide content ranged from 0.43% to 0.57% (the physiological safety limit is less than 1.0%); the temperature was between 32.0 degrees C to 32.2 degrees C; the humidity ranged from 49.7% to 59.4% (the physiological safety limit is the temperature 31 degrees C and the humidity 85% or temperature 38 degrees C and humidity 50%). Each microenvironment parameter met the demand of a healthy person under the normal workload. In the clinical experiments, the doctors wearing the equipment who performed the tracheotomy for a SARS patient in a deep coma were not infected.
  
  
  CONCLUSIONS
  The medical protective equipment can protect the doctor and nurse in SARS contaminated areas effectively and improve their work conditions.
authors.affiliation: School of Material Science and Engineering, Tianjin University, Tianjin 300072, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Tian
authors.forename: Gou-xiang
authors.initials: GX
authors.lastname: Cheng
authors.forename: Zheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Jing-quan
authors.initials: JQ
authors.lastname: Yang
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.forename: Sheng-jun
authors.initials: SJ
authors.lastname: Liu
mesh_terms: D000388:Air / Q000032:analysis; D000391:Air Microbiology; D002245:Carbon Dioxide / Q000032:analysis; D015169:Colony Count, Microbial; D006801:Humans; D006813:Humidity; D009787:Occupational Medicine / Q000295:instrumentation*; D010100:Oxygen / Q000032:analysis; D011482:Protective Devices; D012134:Respiratory Protective Devices; D013696:Temperature; D014691:Ventilation
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen