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Effects of air ionisation on aerocontaminant abatement

 

Content:

1. Effect of air ions on micro-organisms abatement

2. Effect of air ions on virus abatement

3. Effect of air ions on particle abatement

4. Effect of air ions on VOC & Odour abatement

 

1. Effect of air ions on micro-organisms abatement

Krueger & al. (1976), from the laboratory of biometeorology of the University of Berkeley (CA, US) observed that air ion concentrations from 5000 ions/cm3 slow the growth of a variety of bacterial cultures.

 

Every micro-organism in the air is surrounded by water en consequently forms a micro-droplet, called “aerosol”. Challenger (1996) showed that when superoxide reacts with water, low concentrations of H2O2 are formed at the water-air interface. Hyslop (1995) confirmed that H2O2 has bacteriostatic effects on Escherichia Coli and Staphylococcus aureus. Since micro-organisms in the air are always surrounded with a water layer, the most probable action of NAIs on micro-organism is their killing via H2O2.

 

ABC Research Corporation has performed an exhaustive study on four micro-organisms, Penicillium notatum spores, Pseudomonas aeruginosa, Saccharomyces cerevisiae and Staphylococcus epidermis. They have obtained, after 48h treatment with ionisation, average abatement yields above 90% in the air and 70% on surfaces. Mould spores of Penicillium notatum appear to be more resistant, although significant reduction levels do occur. 

 

Micro-organism location:

Airborne

Airborne

On surface

Test:

Air  sampler

Cultivation plate

Swaps

Micro-organism

Abatement efficiency after 48h exposure to air ions

Airborne

98

100

95

Penicillium notatum spores

87

88

61

Pseudomonas aeruginosa

98

93

72

Saccharomyces cerevisiae

99

99

82

Staphylococcus epidermis

99

100

96

 

Literature:

Arnold

JW

Use of negative air ionization for reducing microbial contamination on stainless steel surfaces

2002

J. Appl. Poultry Research, 11, 179-186

Arnold

JW

Use of negative air ionization for reducing bacterial pathogens and spores on stainless steel surfaces

2004

http://www.findarticles.com/p/articles/

mi_qa4105/is_200407/ai_n9457906

Challenger

O

Indoor Air Quality, part 1: negative air ionisation and the generation of H2O2

1996

the science of the total environment, 17, 215-219

Cousins & al

D

Microbicidal effect of negative air ions

1991

J. of Dental Research, 70, 709

Daniels

S.L.

On the ionisation of air for removal of noxious effluvia

2002a

IEEE Transactions on Plasma Science, 30, 1471-1481

Dominique & al

E.L.

Effect of three oxidizing biocides on Legionella pneumophilia, serogroup 1

1988

Applied and Environmental Microbiology, 2, 741-746

Gast & al

R.K.

Application of negative air ionization for reducing experimental airborne transmission of Salmonella enteriditis o chicks

1999

Poultry Sci. ,78, 57-61

Hyslop

P

Hydrogen Peroxide as a potent bacteriostatic antibiotic

1995

Free Radical Biology and Medicine, 19, 31-37

Kellogs & al

E.W.

Superoxide involvement in the bactericidal effects of negative air ions on Staphylococcus albus

1979

Nature, 281, 400-401

Kotaka

Stacy

Effects of air ions on microorganisms and other biological materials

1978

CRC Crit. Rev. Microbiol., 6 (2), 109-49

Krueger

A.P.

Biological impact of small air ions

1976

Science, 193 (4259), 1209-13

Marin

V.

Effects of ionization of the air on some bacterial strains

1989

Annali Di Igiene, 1, 1491-1500

Mitchell

B

Reducing airborne pathogens, dust and Salmonella transmission in experimental hatching cabinets using ESCS

2002

Poultry Sci., 81, 49-55

Mitchell

B

Application of an ESCS for dust, ammonia and pathogen reduction in a broiler breeder house

2004

Appl. Eng. In Agriculture, 20 (1), 87-93

Mitchell

B

ESCS for reducing airborne dust and pathogens - an overview

 

http://www.fda.gov/ohrms/dockets/

dailys/00/oct00/102700/ts00002.pdf

Philips

G.

Effect of air ions on bacterial aerosols

1964

Int. J. of Biometeorology, 8 (1), p27-37

Seo & al

K.H.

Bactericidal effects of negative air ions on airborne and surface Salmonella enteriditis from an artificially generated aerosol

2001

J. Food Protection, 64 (1), 113-116

Shargawi

JW

Sensitivity of Candida albicans to negative air ion streams

1999

J. Appl. Microb., 87, 889-897 or

http://www.blackwell-synergy.com/

links/doi/10.1046/

j.1365-2672.1999.00944.x/full/

 

2. Effect of air ions on virus abatement

Estola (1979) has studied the transmission of the virulent Newcastle virus between different cages of chicken; one cage of chicken has been contaminated with the virus, by direct inoculation in the mouth. Without ionisers, 75% of the chicken located in the surrounding cages died. With ionisers, none of them died. Since viruses are entrapped in water aerosols, their sedimentation resulting from their ionisation and aggregation probably explains this protection effect.

 

Recently, Bioclimatic developed a new concept, combining UV radiation and ionisation, in order to efficiently neutralize viruses entering the device and to encourage sedimentation of virus containing airborne aerosol. See ViroxX

 

Literature:

Estola, T. ,The effect of air ionization on the air borne transmission of experimental Newcastle disease virus infections in chickens, 1979, J. Hyg. Camb, 83, p59-66

 

3. Effect of air ions on particle abatement

Air ions provokes airborne particle aggregation and sedimentation. Air ionisers are recommended for inducing coagulation of particles as small as 0.05µm (Gefter, 2001). If particle sedimentation is a problem, electrostatic filters,, ionising the air prior to its realise in the atmosphere,  is an interesting alternative. See in this section Electrofilters Indoor.

 

Literature:

Gefter, P. Biological aspects of clean-room ionization, 2001,

http://www.ion.com/PDF%20Files/generalionization/biologicalaspects.pdf

 

4. Effect of air ions on VOC & Odour abatement

Standard ionisers can be efficient for VOC abatement in ambient air on condition that their concentrations are lower than 10ppm and their structure is not complex (< 6-7 carbon atoms). The efficiency decreases when the relative humidity increases (Wu & al, 2004). No intermediate VOCs have been identified as product of incomplete ionization due to their very unstable structures (Daniels, 2000b).

 

New concepts of ionizers, integrating a catalyst on their downstream side have been shown to be efficient for VOC abatement, particularly for small molecules, like formaldehyde. The oxidation of more complex molecules, like xylene, is a slower process and asks more air recirculation. See iono-catalysis

 

Odour can be abated via ionisation if the concentration

 

Literature:

Daniels, S. Applications of air ionization for control of VOC and PM, 2002b, http://www.precisionair.com/news/iaq.pdf

Wu, C. Oxidation of volatile organic compounds by negative air ions, 2004, Atmospheric Environment, 38, 6287-6295

 

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