Civil Engineering Reference
In-Depth Information
scale, although the technology available for this is usually only able to target a
specific type of pollutants.
Organic pollutants can be targeted by passive degradation at catalytically active
surfaces. Concerning with this technology include long-term effectiveness, the
accessibility of the bulk air to these surfaces in natural convection regimes and
formation of hazardous secondary products. Most products also require incident
UV radiation to activate the catalytic effect (Cros et al.
2012
; Kolarik and Toftum
2012
; Darling et al.
2012
; Destaillats et al.
2012
).
2.4 Dilution
A further strategy to reduce indoor pollutant levels is diluting the indoor air with
fresh air until acceptable concentrations are reached (Deng and Kim
2007
, Offer-
mann). If the fresh air is targeted to the occupant, this is basically the inverse of local
exhaust. This approach can even be adopted in outdoor environments (Mirzaei and
Haghighat
2010
). A precondition for this strategy is of course the availability of
fresh air with lower pollution levels than those present in the indoor air.
2.5 Alarms
Certain acute airborne health threats, such as carbon monoxide poisoning, require
to alert and evacuate the occupants immediately. In such a case, the sensor has to
target the right pollutants (Abbassi et al.
2012
; Wong et al.
2006
) and be well
positioned to detect the threat as soon as possible (Mui et al.
2006
). In addition to
that, signal processing and integrated modelling can be used to locate the pollution
source, allowing for instance to select an appropriate evacuation scenario (Bastani
et al.
2012
; Chen and Wen
2012
).
3 Ventilation: The Backup Plan
The order of the mitigation strategies listed above reflects their effectiveness in
reducing the risk of incurring adverse effects from exposure to airborne pollution
indoors. The risk chain extends from the actual intake of a pollutant by the
occupant to the concentration of the pollutant in the indoor air and eventually to
the sources of these pollutants. The earlier in this chain the risk is eliminated, the
better. Therefore, source control, or in case of unavoidable sources, local exhaust
should always be the priority. Some sources, especially those related to the bio-
logical nature of the occupants, cannot be reduced with source control and are
moving
through
the
building.
In
that
case,
only
strategies
that
reduce
the
