Hospital Air Cleaner

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The Hospital Air Cleaner is a direct contact dessicant air conditioner, intended to remove airborn bacteria and dust particles (skin and hair flakes) carrying surface bacteria. This device is intended for full high volume airflow use throughout hospitals to reduce incidence of hospital aquired infections, by the removal of pathogens in locations where hepa filtration is not used. It is intended to size the units to provide the air exchange regimes required for different locations in the hospital.

The present machine consists of a cabinet containing a rotating brush fan which draws air from outside. The fan is axially supplied with the concentrated liquid desiccant.The liquid chemical desiccant has biostatic and biocidal properties. The biocidal properties of the desiccant have been tested by University College Hospital in London, UK. Contact of the desiccant with the airflow flowing along the bristles of the brush and producing sub micron particles at the tips which have contact with the air flow within the cabinet provide the required air contact. The continual flushing of the axially supplied desiccant fluid brush fan removes dust particles. Moisture droplets are desiccated further killing bacteria, and possibly some virus material.

The majority of the desiccant is diluted with water vapour from the air and falls to the base of the cabinet together with dust particles to form a reservoir. Fluid is pumped from the reservoir through a filter to remove dust. Then to a boiler to regenerate and re concentrate the desiccant, which will also sterilise it. Residence time in the boiler can be adjusted to destroy pathogens. The desiccant has a boiling point of circa 125C. A finfan cooler is fitted before the reconcentrated desiccant is returned to the fan.

The prototype machine was equiped with an additional dry rotating brush fan at the cabinet outlet intended to capture submicron fluid particles. However some fluid carry over has been experienced. This masked carryover of pathogens since the air samples showed zero development of bacteria due to the desiccant carry over killing everything in the petri dishes.

In the next development machine we plan to have electrostatically charged plates positioned to remove fluid particles from the air flow. Particle size studies have been made of sub micron particles at the Porton Down Research facility in UK. From the particle size distrobution of sub micron fluid particles produced at the fillament tips of the brush fan, we plan to position the spacing of parallel electrostatic plates and suitable charge to remove the bulk of fluid particles that might be otherwise carried over. The plates will be positioned in the upper portion of the cabinet near the air outlet.

Air quality studies can then be performed to determine the efficiency of pathogen removal by air sampling before and after air flow treatment.


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  • Name:
    Stephen Atkinson
  • Type of entry:
  • Patent status: