Negative Air Ions

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.


Effect of Negative Air Ions

  Author Date issuing- journal             Micro crops Treatment Result
1 Universalair


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


(collected on plate surface)

Negative air ion

-30kV DC


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





(1936) Central Laboratory foe the Study ofAeroionification AGAR COLTURE



Vibrio cholerae,



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


negative or positive ions Acceleration of death rate
  Boyko  andSverchkov Industrial Conference onAeroionization in Industrial Hygiene (November 1963 -Leningrad) Micrococcuspyogenes


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



(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


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 comparison
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.