Negative Air Ionization (NAI) has the potential to reduce the concentration of airborne microorganism. The effect is due to the ionization of suspended particles that may carry microorganism, causing them to settle more rapidly on various surfaces, specially metallic and close to the ionization source. Ionization enhances agglomeration, creating larger particles increasing the settling rate. Ionization may create attraction between ionized particles and grounded surfaces. In situation in which dust may carry microorganism, negative air ionization may help in reducing infections.
NEGATIVE IONS – SCIENTIFIC LITERATURE SUMMARY
Effect of Negative Air Ions
| Author | Date issuing- journal | Micro crops | Treatment | Result | |
| 1 | Universalair
Phototech |
October 2001 | Apergillusniger(spores). | OH- radicals | 100% destroyed |
| 2 | IONEX | 2005 | Listeria, Apergillusniger(spores).
Challenge Test : No = 100 ufc on agar
|
About 2x 105/ml,
R.H.>94%, T°= 20°C contact time : 24, 48, 72 h |
No reduction after 72h |
| 3 | Dr. Lorenzo Lodola
Policlinico S. Matteo |
2001 | Head space analyses | About 106/ml | Gas chromatographicpeak of OZONE has been detected, but not yet quantified. |
| 4 | Dr. Lorenzo Lodola
Policlinico S. Matteo |
2001 | Penicilum colony | About 106/ml
Contact time : 3h Room T° andU.R. |
Death of the colony |
| 5 | Dr. Lorenzo Lodola
Policlinico S. Matteo |
Technical Report | Total Count (on 25 cm2) | 3 x 105/ml
contact time not detected (probably some seconds) |
Misleading efficiency of bout 88-100%
Total Count is absent or very low, but the effect has not been proved !! (No challenge has been carried out)
|
| 6 | ILH | Technical Report | Moulds,Rhodotorula rubla,Micrococcusluteus | 3 x 105/ml
contact time not detected (probably some seconds) |
Contamination of the surfaces not detected!
(not in the aim of the study) No Challenge has been carried out
|
| 7 | K.H.Seo, B.W. Mitchell,P.S.Holt,R.K.Gast | Journal of Food Protection, vol.64 no.1,2001
August,31 2000 |
SalmonellaEnteritidis(aerosol)
(collected on plate surface) |
Negative air ion
-30kV DC (O3 <0,01ppm) Trial condition:R.U. = 88% – T =25°C |
93 –98 % after 3 h
(Log red. = 1,68) |
| 7bis | K.H.Seo, B.W. Mitchell, P.S.Holt,R.K.Gast | Ut supra | Ut supra
Recovered with rinse solution |
Ut supra | > 2 Log red. after 3 hours
|
| 8 | Fujimoto – National Inst. Of Fruit Tree Science- Min. odAgr., Fores. & Fisheries | New Techology & Products
September 1998 |
All environmental microbus
(new refrigerator) high humidity 95% ; 0°C |
Negative ions
5 x 104/ml + 0,05 ppm O3
|
Five times longer preservation period of fruits |
| 9 | N.Shayesteh- N.N. Barthakur | Int. J. Biometeorol-1996 | Insects | (omissis) | (omissis) |
| 10 | E.W.Kellogg,M.G. Yost,N.Barthacur, A.P.Kreuger | Nature vol 281
October,4 – 1979 |
Staphylococcusalbus 106 /ml (in buffersolution)(2) | Negative ions flux
0,3 mMol O2–/h (5mA/h) (1) |
6 Log red. After 5 hours
|
| 11 | A.P. Krueger,E.J.Reed | Science
September ,24 1976 – vol.193
|
|||
|
Tchijevski(Moscow) |
(1936) Central Laboratory foe the Study ofAeroionification | AGAR COLTURE
Micrococcuspyogenes,(1974) Staphylococcsuaureus, Vibrio cholerae, Salmonellatyphosa
|
5 x 104/ml
5 x105/ml negative or positive ions |
Growth markedly retarded | |
| R.Fuest | Annual Report -1955 | Neurospora crassa (spores) | negative or positive ions | Inhibits germination of spores | |
| Pratt and Barnard | J.of Am. Pharma.Assos. Sci.-1960 | Penicilliumnotatum | negative or positive ions | Moderate lethal effect | |
| Kingdon | Phis. Med.Biol.-1960 | Escherichia coli | negative or positive ions | killed | |
| Krueger | J.Gen.Phisiol.-1957 | Micrococcuspyogenes
(dropletsuspension) |
negative or positive ions | Acceleration of death rate | |
| Boyko andSverchkov | Industrial Conference onAeroionization in Industrial Hygiene (November 1963 -Leningrad) | Micrococcuspyogenes
(daerosol) |
High concentration of negative ions | No survival after 60 min. | |
| Yaroshenko | Ut supra | ? | 5,2 x 104/ml – 9.5 x 104/ ml | 85% –93 % reduction of control population | |
| Voytsekhovskiy | Ut supra | ? | Less concentration than above | Same results | |
| Phillips (USA) | Int. J. ofBiometeoral 1964
|
Serratiamarcescens
(aerosol droplets< 5 mm) |
Chamber of 365lt volume with negative ions | 78% red. Per minute | |
| Birò and Svab | Med. News (Budapest) 1970 | Micrococcuspyogenes and otherbacteriophages
(aerosol) |
Similar result than above |
(1) : see details in the file Literature.xls
(2) Some evidence indicates that negative ions form a radical on contact with water:
Lotma’s observed that oxygen consumption of liver tissue is increased when the tissue is exposed directly to a negative ions or aqueous medium previously exposed to negative ions.
A.P.Krueger (1975) ion treated water had no effect of viable cell count of M.
On the right it is shown the summary of various tests in which it is evident that ionization only is not 
effective (no sensible reduction of at least 1Log), but combined with ozone, it is working as “accelerator” of the sanitation process. This is essential in air conditioning system because of the short time required by the air to pass through the system and useful for sanitation. This is why also UV lamps are not effective in this application, but only in steady situations.