Ventiliacija

Lack of controllable background ventilation.
Recent research has shown that low levels of background ventilation, without visible mould or dampness, can result in high indoor humidity levels and in greatly increased house dust mite populations. In consequence the average likelihoods given may be an underestimate, and should be considered as conservative.  There should be continuous low-level of background ventilation. Small reductions in the ventilation rate below 0.5 air changes per hour can greatly increase the mite population. Increasing the rate to above 0.7 air changes per hour can also lead to an increase in the mite population in a dwelling which is not adequately heated.

References:
HHSRS worked examples [Online] 2007. CLG Worked examples. 1 damp and mould growth. [cited 4 of March 2013]. Available from Internet:
HHSRS worked examples [Online] 2007. Bristol CC examples. 1 damp and mould growth. [cited 4 of March 2013]. Available from Internet:
HHSRS worked examples [Online] 2007. IDeA examples. 1 damp and mould growth. [cited 4 of March 2013]. Available from Internet:< http://johnpullen.co.uk/downloads.html>
Office of the Deputy Prime Minister [Online] 2006. Housing Health and Safety Rating System. Operating Guidance. Office of the Deputy Prime Minister: London.. [Cited 4 March 2013]. Available from Internet:< http://www.nchh.org/Portals/0/Contents/HH%20Standards.UKHHRSoperatingguidance.pdf>