So far there have been no Polish standards or guidelines
for microbiological quality of indoor air. Furthermore,
there isn’t any European Union directive addressing this;
therefore, it is assumed to be based on particular European
countries’ requirements and scientific propositions [24].
According to current Swedish requirements the number of
500 colony-forming units (cfu) of bacteria and 300 cfu of
fungal spores in 1 m3 can be accepted in an indoor environment
[25]. Especially air contamination caused by fungi is
taken into consideration because of their extremely dangerous
influence on human health. However, it can be noticed
that during the last 20 years opinions concerning innocuous
fungal spore amounts in the indoor air of various kinds of
rooms have varied [26]. According to Berk et al., in 1979
exposure of 20 cfu/m3 to over 700 cfu/m3 has no harmful effect
[27]. Conclusions shown in The Netherlands Research
Methods in Biological Indoor Air Pollution (1989) describe
the amount of fungi over 104 cfu/m3 or the amount of particular
species of mould over 500 cfu/m3 as dangerous for
health. In 2001 the American Industrial Hygiene Association
(AIHA) published a proposition of guidelines for the
amount of fungal spores in different indoor environments,
for example residential and commercial buildings. Guideline
for residential buildings are less than 500 cfu/m3 and for
commercial buildings are less than 250 cfu/m3 [26]. Other
countries’ requirements are similar. In Brazil total amount
of airborne microorganisms (especially fungi) in enclosed
space shouldn’t exceed 750 cfu/m3 [28]. In Hong Kong
good microbiological class air should include less than 1000
cfu/m3 of bacteria. If it includes less than 500 cfu/m3 – air
is classified as excellent [29]. In Singapore requirements for
indoor air quality strictly describe concentration of bacteria
on the maximum level of 500 cfu/m3 [23].