"air is our first         
nutriment & medicine"         
(Hippocrate, 400BC)         
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The physical contaminants


Our ambient air is constantly contaminated with particles produced by human activities and carried by the wind. Fortunately, our atmosphere and our body can efficiently fight against them:
  • the air ionization promotes the particle aggregation; once the aggregates are large enough, their start falling on the floor and on surfaces
  • the mucus film covering our trachea adsorbs most of the inhaled particles, like pollen, dust and micro-organisms. Vibrating cilia coating the trachea continuously expel these particles by lifting them up to the outside.

Nevertheless, in cities and in closed environments, pollution sources like diesel combustion  & cigarette smoke can overload the air with very fine particles smaller than 2.5µm, called PM2.5 particles, what quickly neutralize the air ions, consequently weakening our defence processes.




There are only a European norm concerning the PM10 particles (between 2.5 and 10µm) specifying that their concentration on a yearly basis cannot exceed 40 µg/m3. Unfortunately, there are still no regulation concerning the PM2.5 particles, that are more dangerous. A European regulation should normally prescribe from 2010 a maximal concentration of 25µg/m3 .


Impact on human health


High concentration of PM2.5 particles, like smoke, pollen and flower particles, are dangerous since they can be retained between the alveoli of the lungs, what may provoke lung cancer. A Dutch study on 5000 volunteers has shown that people living near major roads were more likely to die from cardiopulmonary disease or lung cancer (Hoek & al, 2002).


A study on 500,000 individuals concluded that when air pollution levels suddenly increases, in addition to cardiopulmonary disease, there was an unexpected increase in the number of deaths related to heart attacks and stroke, as well as asthma and pneumonia. They found an obvious correlation between the concentration of PM2.5 particles and the human death rate. ( Arden Pope & al, 2002)


Cigarette smoke contains also submicronic sticky oil aerosols (tars) that can also affect the mucus and the lungs and cancerous aromatic molecules like benzene and its derivates.


High concentrations of fine particles also dramatically neutralize the negative air ions, crucial for the air purification and for the activation of our vital body functions, leaving high concentrations of positive air ions in our environment.


Krüger & al (1963) found that an excess of positive ions inhibits the mucus production and consequently the good working of this expel process, leading to toxic deposits in the trachea and the bronchia. This leads to cough problem, body oxygenation reduction and illnesses like cancer (Robert, 1991). On the other side, Krüger & al (1963) have shown that the NAIs promote the mucus production and the good working of the cilia.

Impact on the Air Purification or Conditioning Concept


For any kinds of application, it is essential that the air purification system is able to:



Appropriate technology


drastically abate the concentration of the PM2.5 particles, even the sticky ones, if possible without creating pressure drop increase



produce high concentrations of negative air ions in order to accelerate their aggregation and to at least recreate the natural balance between positive and negative air ions


Negative Air Ion Generators


© 2008 Air Quality Concept