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Indoor Air Quality (IAQ) 


Indoor air quality or IAQ is a term which refers to the quality of air inside your home or office. It is also the process of understanding and monitoring the air you breathe and managing the common indoor pollutants thereby reducing the immediate health problems as well as future health effects years after exposure.

What is IAQ


People spend most of their time at homes, offices, public transport and other indoor environment. The quality of air in the indoor environment has a significant impact on human health.


Prevention is better than remediation plan. By understanding indoor air quality, we can create evidence-based infection control practices during this pandemic and epidemic prevention measure. Poor IAQ can lead to discomfort, ill health (e.g., headache, itchy eyes, respiratory difficulties, skin irritation, nausea and fatigue) or even global pandemics. Good IAQ in offices and public places not only enhance comfort level of the occupants and increase productivity of the workers, but also can sustain economic growth of a country when outbreak stands globally.


To improve the IAQ and promote public awareness of the importance of IAQ, the HKSAR Government has implemented an IAQ Management Programme. A core element of the Programme is to launch a voluntary IAQ Certification Scheme for Offices and Public places so as to elevate a good IAQ management practices.


As a leading testing laboratory, QPT is expert in assessing indoor air quality (IAQ) and provides professional advices on air quality management. We provide wide range of services included air sampling, testing and analysis.


QPT is an accredited laboratory and all required IAQ parameter measurement is accredited under Hong Kong Laboratory Accreditation Scheme (HOKLAS).


IAQ Objectives

A set of 2-level IAQ objectives is established to act as the benchmark for evaluating and assessing IAQ under the IAQ Certification Scheme.

They are classified in:

"Excellent" Class — an excellet IAQ that a high-class and

             comfortable building.

 "Good" Class  — that provides protection to the public at

           large including young and elderly.

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IAQ Objectives for Office Buildings and Public Places

(Effective on 1 July 2019)

Table 1: Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places (2019). January 2019.

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Assessment of IAQ Parameters

There are 10 parameters in IAQ Objectives for Office Buildings and Public Places. The general information about the assessment of individual parameters of the IAQ objectives would provide in the following. 


Carbon Dioxide (CO2)

The carbon dioxide indicated when the ventilation rate is low and other airborne contaminants are accumulating. Also, levels of carbon dioxide vary with occupancy during the day in offices.

Carbon Monoxide (CO)

The level of carbon monoxide may increase if vehicle exhausts are trapped, the location of fresh air intake is in close proximity to roads of heavy traffic, car park or industrial exhaust, or where the source of combustion is present indoors.

Respirable Suspended Particulates (PM10)
It describes a variety of particulates with a nominal aerodynamic diameter of 10 micrometers (μm) that are small enough to be suspended in air.

Sources of these particles can be categorised as

- microbial particulates (e.g. bacteria, virus, and mould),

- animal and plant particulates (e.g. pollen and insect parts),

- mineral particulates (e.g. asbestos and man-made mineral fibres),

- combustion particulates (e.g. emissions from cooking and heating appliances) and so on.

Nitrogen Dioxide (NO
Similar to carbon monoxide, a high level of nitrogen dioxide may exist if there is a combustion source indoor, vehicle exhausts are trapped, or location of fresh air intake is in close proximity to roads of heavy traffic, car park, or industrial exhaust.

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Ozone (O3)
Ozone can be produced by equipment that utilises ultraviolet light or causes ionisation of air. This includes photocopiers, laser printers and ionisers.

Formaldehyde (HCHO)
High level of formaldehyde may be present if there are renovation and/or refurbishment (e.g., new carpets, particleboard, fabrics and new wooden furniture) within the last 3 months of the locations where substantial volume of cleaning fluids and adhesives are being used.

Total Volatile Organic Compounds (TVOC)
VOCs may enter from the outdoor environment, or be emitted from building materials, cleaning agents, cosmetics, waxes, carpets, furnishings, laser printers, photocopiers, adhesives and paints used indoors.

Radon (Rn)
Granite is very widely used in Hong Kong buildings and hence may have the potential of radon emission. If a building is not well ventilated, the emitted radon will become trapped and accumulated.



Airborne Bacteria
In air-conditioned buildings, water or condensation in ventilation systems can act as breeding grounds for harmful bacteria which are then dispersed through the ventilation process.

Mould growth is promoted by high humidity and materials with high moisture content. Once mould growth occurs, it can damage food, textile, leather, carpet and various building materials.

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Flowchart for application Procedure of IAQ certificate

Table 2: A Guide on Indoor Air Quality Certification Scheme for Offices and Public Places(2019)
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