2
A PRACTICAL APPROACH TO INTEGRATED INDOOR
AIR MITIGATION: GRAPH INVARIANTS CORRELATION
AND SUBFLOOR-VENTILATION LAB TESTS

N. L. Helal 1) , F. Steinhäusler, and R. Winkler
Institute of Physics and Biophysics,
University of Salzburg, Hellbrunnerstrasse 34, A-5020 Salzburg, Austria
Tel. no. +43-662-8044-5700; Fax no. +43-662-8044-150; e-mail: Physik@sbg.ac.at

Radon as an indoor air pollutant has been extensively researched worldwide over the past thirty
years. However, radon is only one of several other important pollutants present in the indoor
atmosphere. In addition to radon as an ubiquitous indoor pollutant, the simultaneous presence of
other non-radiological pollutants, such as toxic alkanes found in the working environment, needs to
be accounted for its integrated mitigation approach. Application of graph theory facilitates the
study of these chemicals, using different relations (linear, logarithmic, polynomial, power and
exponential) between graph invariants and the properties under study. In comparison to radon, data
on exposure levels, inhalation dosimetry, and potential health effects for these non-radiological air
pollutants is rather limited. This leads to a dissatisfactory situation with regard to mitigating the
indoor environment: on the one hand there is the growing awareness for the need of an integrated
approach to indoor mitigation, accounting for the relevant contribution of various pollutants; on the
other hand, there are severe constraints in terms of manpower and financial resources, limiting the
extent to which these non-radiological pollutants can be researched, when the public health policies
require practically implementable advice in the near future.
In recognition of these predicaments a new pragmatic approach was taken:
a) a screening method was developed for assessing the potential of a suspected pollutant to
induce health effects using graph invariants correlation analysis (GICA);
b) a simulation method was developed for conducting simplified tests on the widely used
subfloor-ventilation technique under defined laboratory conditions, simulating the subsoil-pipe
system with an automated soil-filled test chamber (ASTC). The ASTC is equipped with
multiple sensors and externally controlled mechanical ventilation.
GICA was applied to seven alkanes found in the working environment (butane, pentane, hexane,
octane, nonane, cyclohexane, trimethyl benzene). There is satisfactory correlation (r>0.7) between
the different graph invariants and the threshold limit value-time weighted average concentration
(TLV-TWA). The ASTC-experiments demonstrated the capability of this laboratory-system to
allow a prediction of the performance characteristic for a given subfloor-ventilation system and
certain environmental conditions.

Key words: mitigation, subfloor, invariants, regression analysis, alkanes