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Issue 16, June 2005
Indoor Pollutants
The Indoor air
pollutants in your office environment can generally be
categorised into five main types generated by different sources:
External –
usually indicated by the presence of carbon monoxide generated from a
combustion source such as vehicle exhaust;
Occupant – usually detected as elevated carbon dioxide, by
odour and the presence of dust;
Operational – usually ozone, cleaning chemicals and office
equipment;
Furnishings and content – generally present as formaldehyde and
retained solvents (TVOCs), generated from wood products,
printed materials, paints, carpets and
Air-conditioning systems – dust, microbial (bacteria, moulds
and fungi).
Recommended Acceptable Levels for Indoor Pollutants
The list below gives generally accepted guidelines for indoor air
quality (IAQ), but it does not guarantee the health of all individuals
and is subject to appropriate sampling and measurement.
Carbon Dioxide
The
ASHRAE Standard 62-2004 and
WHO
standards guideline both recommend maximum value of 1,000 ppm for
indoor air quality. Carbon dioxide arises from human respiration and
combustion sources, eg motor vehicles, gas burning and it excessive
levels can reduce oxygen uptake causing drowsiness and lethargy.
Carbon Monoxide
The exposure to carbon monoxide is recommended not to exceed 9 ppm
as set by
NHMRC guidelines (Ambient Air quality Goals and Interim National
Indoor Air Quality Goals Recommended by NHMRC, Publications May 1996).
Carbon monoxide arises mainly from automotive exhausts.
Total Volatile Organic Chemicals
The term TVOC encompasses a very large and diverse group of
carbon-containing compounds, including aliphatic, aromatic and
halogenated hydrocarbons, aldehydes, ethers, esters, acids, alcohols and
ketones.
At present there are
few standards governing exposures to specific VOC contaminants in
non-industrial buildings. The NHMRC recommends that total VOCs have a
maximum permissible level of 500 micrograms/m3 with the
recommended limit for acceptable indoor air quality of a single
compound should not contribute more than 250 micrograms/m3.
Polar Volatile Organic Chemicals
Polar volatile organic compounds (PVOC) are a subclass of volatile
organic compounds and typically denotes those containing oxygen. They
are often the underlying cause of odour complaints. Formaldehyde
is an important element of PVOCs and typically originates from
phenol formaldehyde or urea formaldehyde based chemicals used to the
manufacture a number of interior products (e.g. medium density
fibreboard used in manufacture of desk and furniture). It may also arise
from the use of inappropriate cleaning products. Other specific
examples of PVOCs include methylated spirits and ketone solvents, but
also include odorous chemicals (e.g. perfumes used in cleaning and
personal care products) and some microbial emissions.
The CETEC recommended maximum for acceptable indoor air quality
for PVOCs is 200 micrograms/m3 . The NHMRC only has a
recommendation that the formaldehyde level be below 0.1 ppm.
Airborne Microbiological Content
Micro-organisms are present in almost every environment found, soil,
water, food and air. Micro-organisms are relevant to issues of
IAQ as they may:
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Cause infections
and allergies;
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Accelerate
deterioration of plant and buildings;
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Produce odorous
volatile compounds;
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Reduce performance of
ducts, filters and coils and
-
Block drains in
plant rooms.
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 1,000 total viable colony forming units (cfu) per m3 is
acceptable. CETEC's experience indicates as a general rule
maximum microbial level of 500 cfu/m3 is more relevant.
The nature of the biological species is important and there should not
be amplification above outdoor levels.
Particulates
NHMRC guidelines suggest only a total suspended particles 90
micrograms/m3 upper limit. Commonly, 30% of total
suspended particles is PM10 (respirable particulate matter -
less than 10 microns in diameter), thus CETEC suggests a practical
acceptable limit of 30 micrograms/m3 for PM10.
Particulate composition is important so analysis of dust is required
for a risk assessment. Asbestos and synthetic mineral fibres are
governed by state OH&S regulation with a health related limit of 0.1
fibres per millilitre of air. Glass fibre limits and disposal methods
require expert evaluation.
CETEC offers a range of services from basic facility IAQ
assessment, assisting with the design of new facilities through to
investigating and resolving 'sick buildings'.
To give us feedback on
this article or to ask how CETEC can help you then contact us
here.
To
read other related articles:
Indoor Air Quality - health effects of VOC's
Low-VOC Emitting Building Products (2007
article)
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