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Alisea News

05/11/2015

Legionellosis risk at schools: how to prevent it?

Legionellosis often represents a not considered risk in biological risk evaluation of schools, but epidemics have been discovered in environments like schools, hotels and hospitals

24/10/2015

Evidences of legionellosis in a Capannoli plant

Security measures has been immediate for the infected rooms. These measures have been activated by a major's decree to debilitate the dangerous bacterium


Hazards

Poor hygiene in aeraulic systems can be hazardous to the health of those exposed to a series of contaminants and microorganisms which are harmful to the respiratory system

Why is prevention necessary?

The risk from exposure to and the concentration of contaminants in confined spaces is from 10 to 50 times higher than outdoors. People from developed countries spend around 75% of their time inside buildings: for this reason effective prevention is necessary to protect human health.

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Aeraulic contamination

An aeraulic system, during its life and due to its function physiologically faces two different kinds of contamination:

  • Chemical contamination due to the accumulation of polluting particles;
  • Microbiological contamination due to the proliferation of bacteria, viruses, molds and yeasts.
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Aeraulic imbalance

An aeraulic system can also become imbalanced, suffer a sharp deterioration in environmental parameters from a physical, chemical or microbiological point of view. This is due to the fact that an imbalanced system is no longer able to:

  • Transmit the correct temperature and humidity to the environment;
  • To produce the right amount of fresh air;
  • To filter and dilute indoor contaminants.
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Why is prevention necessary?

In 1998, for example, the EPA (Environmental Protection Agency – USA), through the IEMB (Indoor Environment Management Branch), compared the level of concentration and exposure to several air pollutants recorded in the indoor environment with the level recorded in the outdoor environment.

Data analysis confirmed that resulting indoor concentrations are generally from 1 to 5 times higher than outdoor ones and that exposure to indoor contaminants is from 10 to 50 times higher than outdoor exposure.
Since people in developed countries spend most of their time (about 75%) inside buildings or in other confined spaces, it is easy to understand why the phenomenon of indoor pollution has become of prime importance with a view to effective protection of human health.

In this context aeraulic systems are one of the main causes of the deterioration of indoor air, because over time, due to their structure and function, they are subject to possible imbalance and physiological phenomena and contamination.

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Aeraulic contamination

There are two main dangers of contamination of indoor air deriving from an aeraulic system in poor hygienic conditions:

  • The danger of chemical contamination

    due to an accumulation of polluting particles in the system coming from outside (through the external air intake) and from inside the building (through the recovery or recirculation circuit);
  • The danger of microbiological contamination

    caused by the proliferation of animal microorganisms (bacteria and viruses) and fungi (moulds and yeasts) inside the system.
    In particular the main microbiological agents detected in aeraulic systems are:
    1. Bacteria: Staphylococcus Aureus, Pseudomonas Aeruginosa, Legionella Pneumophila, Legionella Gormani;
    2. Viruses: Rhinovirus, A and B Influenza viruses, Parainfluenza virus, Coronavirus, Adenovirus;
    3. Fungi: Aspergillus, Cladosporium, Penicillium, Paecylomyces, Cephalosporium, Fusarium, Streptomycin, Trichoderma.


The World Health Organisation (WHO), at the end of a series of studies carried out over the past twenty years by groups of researchers from different nations, from different latitudes, on workers with comparable but not overlapping tasks and work rhythms, showed how chemical-biological contamination deriving from poorly hygienised air conditioning systems are one of the main causes of various types of pathologies among which there should certainly be listed:

  • the Sick Building Syndrome

    which is not imputable to an identifiable etiological agent and which presents symptoms such as asthenia, headaches, coughing, and a feeling of thoracic constriction, irritation of the mucous and of the skin, burning and red eyes and general discomfort. These symptoms occur in a high percentage of exposed subjects and are chronologically associated with work activities, because they often decrease or disappear by moving away from the unhealthy environment;
  • the Building Related Illness

    i.e. those pathologies caused by bacteria, fungi, viruses and those deriving from dust and chemical contaminants. These pathologies, which are more serious than those mentioned previously, present a generally uniform clinical picture, a well identified etiology, defined clinical and laboratory signs, a long recovery despite moving away from the building and the need to remove the contaminating agent in order for the patient to get better.
    These pathologies occur with a low prevalence among the occupants of a building.
    To this group of pathologies the following are attributable:
    • Infectious Syndromes: “Legionnaires Disease” ( or Legionellosis) , “Pontiac Fever”, Flu-like Symptoms, Tuberculosis;
    • Allergic Syndromes: Extrinsic Allergic Alveolitis, Bronchial Asthma, Dermatitis, Rhinitis, and Contact Urticaria;
    • Immunological Syndromes: Hypersensitivity Pneumonitis, “Humidifier Fever”.
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Aeraulic imbalance

An aeraulic device is technically defined “imbalanced” when it undergoes a permanent alteration of its ability to operate: in order mainly its ability to:

  • transmit the thermal-hygrometric load planned by the project to the indoor environment;

  • transmit the quantity of fresh air planned by the project to the indoor environment;

  • filter and dilute indoor contaminants.


An aeraulic system can become imbalanced due to a series of reasons of which the most common causes are:

  1. poor maintenance activities which alter the settings and the calibrations originally provided by the project. (e.g. accidental tampering of components directing the air flows;
  2. failure to adapt the system to the changing conditions of the people within the indoor environment which it is serving. (e.g. an increase or decrease in the number of occupants in an environment);
  3. failure to adapt the device to changing volumes of the indoor environment it is serving. (e.g. changing the outlay of furniture that causes alterations in the volume of the environment).

The ultimate consequence of an imbalance in the aeraulic system is a direct worsening of the environmental parameters from a physical, chemical and microbiological point of view.

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