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home ::
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contact The benefits
of undertaking audits of the Indoor Air Quality is widely known and
heavily promoted, however the available documentation is of a
scientific or medical nature and is not aimed at assisting the
Facility Manager or Building Owner. This article aims to help
you by providing an easy to understand guide.
There are two distinct
levels of IAQ surveys that can be undertaken:
- Annual IAQ/IEQ review or baseline audit
This audit looks at generic contaminants
that are readily tested and provides an indication of the quality of
the indoor air:
- Occupant comfort factors:
- Temperature and relative humidity:
Temperature and humidity within a building is
dependant on the type and effectiveness of air condition
system.
In Australia it is generally agreed that the
acceptable temperature range for indoor air quality is 20 to
26 ° C, depending on the season (Comfort at Work, Fact Sheet #21,
NOHSC Publication, website, 2003).
In general, the range of humidity levels
recommended by different organisations is 30 to 60%. ASHRAE
state that relative humidity between 35 and 60% provides the best
conditions for human comfort, reduces growths of bacteria and
other microbes and reduces the rate at which chemical interactions
occur (HVAC Systems and Equipment. ASHRAE Handbook ASHRAE Atlanta
2000).
Indoor air pollutants in an office environment
can be categorised into five main types generated by different
sources as detailed below:
Monitoring of CO2 provides an
indication of the effectiveness of the air conditioning system at
removing stale air and providing sufficient fresh air into
the building to prevent contaminants from building up to
unacceptable levels.
The ASHRAE Standard 62-2001R and WHO standards
suggest a recommended maximum value of 1000 ppm.
The recommended values for exposure for carbon
monoxide should not exceed 9 ppm as set by The Australian
National Health and Medical Research Council (NHMRC) guidelines
(Ambient Air Quality Goals and Interim National Indoor Air Quality
Goals Recommended by NHMRC, Publications May 1996).
- Airborne particulates less than 10 microns.
Australian Standard AS1668.2-2002 (Ventilation
design for indoor air contaminant control) recommends a PM10
of 50 m g/m3 maximum for outdoor air. There is no
similar PM10 standard for indoor air. NHMRC guidelines
suggest total suspended particles of 90 m g/m3 maximum
limit. An established practice is take one half to one third of
this value, namely 30 m g/m3 to 45 m g/m3,
as indicative of indoor PM10.
- Airborne bacteria, mould and fungi concentrations.
At present there is no regulatory or prescribed
environmental criterion to determine whether a measured
airborne level of bacteria, mould or fungi is a risk factor
with regard to human health. ACGIH Biological Exposure Indices
suggest that a microbial level up to 1000 total viable colony
forming units (cfu) per m3 is acceptable.
- Air monitoring for volatile organic compounds (VOC’s).
VOC’s are present within the built environment
and are used in paints, solvents and adhesives. They are released
into the air due to off-gassing from carpets and furniture.
The NHMRC recommends that total VOC’s have a
maximum permissible level of 500 m g/m3 with the
recommended limit for acceptable indoor air quality of a single
compound should not contribute more than 250 m g/m3.
- Inspection of the building and air handling units.
A visual inspection of the air handling units and
the building is important in establishing the condition of
the system and providing an indication of the level of appropriate maintenance.
A properly designed and maintained air conditioning system is
critical in providing an acceptable IAQ within a building. The air conditioning system is typically the predominant mechanism
in providing fresh air and the removal of indoor contaminants. A
poorly maintained system may not be effective in removing
contaminants and may act as a source of contaminants if not
designed, installed or maintained effectively.
- IEQ incident investigation
This audit obtains details of
an incident by discussions with management and individuals
involved or affected by the incident.
Contaminants tested within
this investigation include the items mentioned above to obtain an
understanding of the IAQ simultaneously with the discussions.
Additional air sampling, monitoring and investigations may be required
depending on the outcome of the preliminary monitoring and
discussions to identify the cause of the incident.
CETEC has carried out major IAQ/IEQ and OH&S investigations and regular IEQ surveys for the private and public
sector. Please contact us
here to
start or improve your
indoor environmentr quality. |
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