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

AuthorDate issuing- journalMicro cropsTreatmentResult
October 2001Apergillusniger(spores).OH- radicals100% destroyed
2IONEX2005Listeria, 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
3Dr. Lorenzo Lodola
Policlinico S. Matteo
2001Head space analysesAbout 106/mlGas chromatographicpeak of OZONE has been detected, but not yet quantified.
4Dr. Lorenzo Lodola
Policlinico S. Matteo
2001Penicilum colonyAbout 106/ml
Contact time : 3h

Room T° andU.R.
Death of the colony
5Dr. Lorenzo Lodola
Policlinico S. Matteo

Technical ReportTotal 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)
6ILHTechnical ReportMoulds,Rhodotorula rubla,Micrococcusluteus3 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
7K.H.Seo, B.W. Mitchell,P.S.Holt,R.K.GastJournal of Food Protection, vol.64 no.1,2001
August,31 2000
(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)
7bisK.H.Seo, B.W. Mitchell, P.S.Holt,R.K.GastUt supraUt supra
Recovered with rinse solution
Ut supra> 2 Log red. after 3 hours
8Fujimoto – National Inst. Of Fruit Tree Science- Min. odAgr., Fores. & FisheriesNew 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
9N.Shayesteh- N.N. BarthakurInt. J. Biometeorol-1996Insects(omissis)(omissis)
10E.W.Kellogg,M.G. Yost,N.Barthacur, A.P.KreugerNature 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
11A.P. Krueger,E.J.ReedScience
September ,24 1976 – vol.193
Tchijevski(Moscow)1936) Central Laboratory foe the Study ofAeroionificationAGAR COLTURE


Vibrio cholerae,

5 x 104/ml
5 x105/ml

negative or positive
Growth markedly retarded
R.FuestAnnual Report -1955Neurospora crassa (spores)negative or positive
Inhibits germination of spores
Pratt and BarnardJ.of Am. Pharma.Assos. Sci.-1960Penicilliumnotatumnegative or positive
Moderate lethal effect
KingdonPhis. Med.Biol.-1960Escherichia colinegative or positive
negative or positive
Acceleration of death rate
Boyko andSverchkovIndustrial Conference onAeroionization in Industrial Hygiene (November 1963 -Leningrad)Micrococcuspyogenes
High concentration of negative ionsNo survival after 60 min.
YaroshenkoUt supra?5,2 x 104/ml – 9.5 x 104/ ml85% –93 % reduction of control population
VoytsekhovskiyUt supra?Less concentration than aboveSame results
Phillips (USA)Int. J. ofBiometeoral 1964Serratiamarcescens
(aerosol droplets< 5 mm)
Chamber of 365lt volume with negative ions78% red. Per minute
Birò and SvabMed. News (Budapest) 1970Micrococcuspyogenes 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
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.