Ventilation: Thermal Efficiency and Health Aspects - Nearly Zero Energy Building Refurbishment - page 378

showering (moisture) to the intensive use of cosmetics and cleaning products
(VOCs) (Kwon et al. 2008 ; Steinemann et al. 2011 ; Moran et al. 2012 ). Likewise,
as with material emissions, emissions from household products may trigger sec-
ondary chemical reactions (Coleman et al. 2008 ; Updyke et al. 2012 ).
Building activities (Kumar et al. 2012 ) and painting (Celebi and Vardar 2008 )
are often large temporary sources. In office environments, large amounts of par-
ticles are released by laser printers (Salthammer et al. 2012 ; Jayaratne et al. 2012 ;
Byeon and Kim 2012 ). The operation of building services, such as HVAC unit, can
resuspend previously deposited particles (Wang et al. 2012 ). Ill-conceived or ill-
maintained building services can also become sources of biological contaminants
such as odours, VOCs, mould spores (Clausen 2004 ; Schleibinger and Rüden
1999 ) and Legionella bacteria (Cooper et al. 2004 ; Stout and Muder 2004 ).
The occupants themselves are sources of carbon dioxide, moisture, bio-effluents,
bacteria, viruses, etc. (Gao and Niu 2006 ; Hathway et al. 2011 ; Olmedo et al. 2012 ;
Zhang et al. 2011b ). Due to the movement of the occupants, these pollutants are
usually dispersed throughout the entire building (Choi and Edwards 2012 ; Spitzer
et al. 2010 ; Wang and Chow 2011 ) and often continuously resuspended (Stranger
et al. 2008 ). Particularly high exposures can be found in episodes of (unintended)
inter-occupant contact, such as cough or sneeze (Redrow et al. 2011 ). Self-evidently,
overcrowding increases the intensity of these sources (Firdaus and Ahmad 2012 ).
1.2.3 Outdoor Environment
Although the basic idea of ventilation is that the outdoor air is less polluted than
the indoor air, some pollutants are mainly produced in the outdoor environment,
e.g. traffic-related emissions and emissions from industrial processes. Other, even
typically indoor, pollutants may not have sources in a specific building, but are
found in the ambient air (Longinelli et al. 2011 ). These pollutants are therefore
brought into the indoor space through air exchange with the outdoor environment
(Sangiorgi et al. 2013 ; Hodas et al. 2012 ). Typical determinants of outdoor pol-
lution levels are of course the proximity (Amato et al. 2011 ) and timing of the
outdoor sources (Menut et al. 2012 ; Haas et al. 2013 ), such as locations near busy
traffic on rush hours (Lim et al. 2011 ; Lobscheid et al. 2012 ) or dense cities (Lu
et al. 2011 ), but modifying factors such as meteorology (Liu et al. 2012 ) and the
proximity of other buildings can have a significant impact on indoor concentra-
tions (Mavroidis et al. 2012 ).
2 Exposure Risk Management Strategies
A number of approaches can be adopted to avoid the adverse effects caused by
exposure indoors. Such risk management strategies include reducing the strength
of known sources, local exhaust around known sources, eliminating airborne