The UNI 10339:95 norm on indoor air quality

A triple approach

A triple approach

Indoor air quality is determined by the percentage of contaminants in the environment that can cause discomfort or health damage. These contaminants can be microorganisms of various kinds such as insects, bacteria and viruses. There are three different approaches to understanding the healthiness level of indoor air:

  1. prescriptive approach: the minimum or maximum air flow rates per person (or per m2 of surface area) are prescribed according to the category and intended use of the building (UNI 10339:1995);
  2. performance approach: once the pollutant concentration limits have been set, the external air flow rates must guarantee these limits (this method requires knowledge of the pollutants and sources);
  3. olfactory approach: concentrations of pollutants are limited so as to reduce the olfactory perception of pollutants.

To apply these methods it is necessary to estimate the total sensory pollutant load and determine the air flow rate sufficient to keep the percentage of people dissatisfied with the air level below a certain threshold.

Current legislation and EU directives

Current legislation and EU directives

In force since 1995, but subject to revision, the main technical standard on the subject is UNI 10339:95. In recent years, however, the European Community has issued a number of directives on improving indoor air quality that have required revision.

One of these is EN 13779, the basis for the modification of UNI 10339 by the CTI (Comitato Termotecnico Italiano), which has already been put out to public enquiry. The standard provides, among other things, indications for the classification and definition of the minimum requirements of the systems and the values of the reference quantities during their operation.

UNI also identifies the parameters and limit concentration rates of the various pollutants (sulphur dioxide, particulate matter, carbon monoxide, ozone, nitrogen dioxide, lead) for assessing air quality.

The position of the external air intake is also important for indoor air quality: the standard defines where it should not be located. In any case, both the outside air and the recirculated air must be filtered using filters of an appropriate class, depending on their efficiency.

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