Indoor Air Pollutant

1. What are the causes of indoor air pollution?

The primary cause of indoor air pollution is the emission of polluting gases or particles indoors. The poor outdoor air quality also brings in air pollutants and odour into the ventilation system of the building. Inadequate ventilation can increase indoor air pollutant levels by not bringing in enough fresh air to dilute the pollutants and carrying them away. High temperature and humidity levels can also increase concentrations of some indoor air pollutants, such as formaldehyde or bacteria.

2. What are the common indoor air pollutants found in air-conditioned buildings?

Common indoor air pollutants found in air-conditioned buildings include carbon dioxide, respirable suspended particulate, formaldehyde, total volatile organic compounds and airborne bacteria. The level of some combustion products like carbon monoxide and nitrogen dioxide may be high if there is a carpark close to your premises or burning stoves are used indoors (e.g. in barbecue restaurants). Elevated level of nicotine and respirable suspended particulates is not uncommon when there is smoking activity in the premises. In addition, the level of ozone may be high if a number of ozone emitting office equipment like laser printers, photocopiers, fax machines, are used in office without sufficient ventilation. For details, please refer to the IAQ leaflet entitled “Indoor Air Quality and You” published by the Environmental Protection Department (EPD).

Health Effects of Indoor Air Pollution

3. What are the health effects due to poor IAQ?

Health effects due to poor IAQ may include immediate effects and chronic effects:

Immediate effects

Immediate effects may include irritation of the eyes, nose, headaches, and fatigue after exposure to high concentrations of indoor air pollutants. Such immediate effects are usually short-term and treatable.

Chronic effects

Some health effects may show up only years after exposure has occurred or after long or repeated periods of exposure, such as respiratory diseases, heart disease, and even cancer.

4. What is “sick building syndrome”?

It is used to describe situations in which building occupants experience acute health and discomfort effects that appear to be linked to the time spent in a building. The symptoms include:

  • headache
  • itching and irritation of the eyes
  • nose and throat irritation
  • dry cough
  • itchy skin
  • dizziness and nausea
  • poor concentration
  • fatigue
  • sensitivity to odour

The cause of the symptoms is not known. The symptoms tend to relieve or disappear soon after leaving the building.

5. What is radon and how does it affect our health?

Radon is a radioactive gas with chemical symbol Rn. It is emitted from earth, rock, granite, and building materials. Radon is a confirmed human carcinogen. Radon has increased the number of lung cancer incidents in the United States substantially in the past years. High radon level inside indoor environment can be avoided by maintaining good ventilation, and using wall paper as barrier to radon gas emitted into the indoor air. For details, please refer to the IAQ leaflet entitled “Radon and You” published by the EPD.

6. How does formaldehyde affect the IAQ?

Formaldehyde is a common indoor air pollutant. It is a colourless chemical gas with a pungent odour at high concentration. It is highly irritating to the eyes and respiratory tract. Prolonged exposure to formaldehyde may lead to hypersensitivity and damage to respiratory system. Furthermore, formaldehyde is a known carcinogen to human beings.

The major emission sources of formaldehyde in indoors air are pressed-wood products, adhesive materials, particle board, medium-density fibreboard, as well as other decorative materials like foam insulation, fabrics, carpets and floor coverings. In addition, formaldehyde is also emitted from burning cigarettes, combustion sources such as gas appliances and kerosene heaters, or certain types of consumer products such as paper products and cosmetics etc.

7. What are the health effects of environmental tobacco smoke (second hand smoke)?

Environmental tobacco smoke (ETS) (or second hand smoke) is a mixture of smoke given off from a burning end of a cigarette, a cigar, or other tobacco products and exhalation from smokers. ETS consists of mainly particulate matters, nicotine, formaldehyde, carbon monoxide and over 4,000 other chemicals. Some of them are confirmed human carcinogens. ETS causes health effects such as irritation of eye, nose and respiratory tract, headache, cough, and even lung cancer. Local studies also found that non-smoking women have increased risk of lung cancer if their husbands smoke. For children, ETS increases the risk of lower respiratory tract infection such as bronchitis, pneumonia, and infection of ear. Odour of ETS also causes nuisance to the people around you. For details, please refer to the IAQ leaflet entitled “Environmental Tobacco Smoke and You”(Second Hand Smoke).

8. What are the potential health risks of mould?

Inhaling mould spores and particles or touching mould patches may cause allergic reactions to mould-sensitised individuals. Symptoms other than allergic and irritant types are not common. There is no threshold for the health effects of mould, but it is advisable to remove all visible mould growth and apply remediation measures irrespective of the extent of mould growth. 

9. What is Legionnaires' disease?

Legionnaire’s disease is a form of pneumonia caused by a bacterium, Legionella pneumophilia. It was first discovered following an outbreak at an American Legion convention in a Philadelphia hotel in 1976. Legionella is normally present in small quantity in potable water supplies. Under the right conditions (particularly moderately hot water temperatures, from about 20 degree Celsius to 45 degree Celsius, and in the presence of nutrients), its population may greatly increase. If droplets of contaminated water get into the air and are inhaled by a susceptible individual, they may contract such disease.

Amongst the recognized sources of infection is cooling towers for the central air-conditioning system. There have been documented cases of individuals being infected by the Legionella bacteria in the water droplets from a cooling tower.

For details, please refer to the leaflet entitled “Understanding Legionnaires’ Disease and Its Prevention” published by the Electrical and Mechanical Services Department.

Mitigation Measures to Improve IAQ

10. How can we improve the IAQ in air-conditioned buildings?

We can contribute to improving the IAQ of our air-conditioned buildings. Here are something you can do:

  • Maintain adequate air ventilation. Do not block air vents and ducts.
  • Do not smoke inside indoor environment.
  • Report to building management in case of water leakage to avoid the growth of micro-organisms.
  • Dispose of perishable food products properly to avoid generating unpleasant odour.
  • Report to building management for IAQ problems.

If you are an office manager, you can do the followings to improve IAQ:

  • Cooperate and work closely with the building management.
  • Make sure proper air ventilation inside the office.
  • Keep the place clean and dry.
  • Select products with no or low volatile organic compounds.
  • Provide a separate ventilation system for pollutants-generating equipment.
  • Replace carpet, false ceiling, etc when odour, water marks and even mouldy marks are detected.

If you are a property manager, you can do the following to improve IAQ:

  • Appoint an IAQ manager who serves as the contact for indoor environmental issues.
  • Arrange a scheduled cleaning and maintenance programme for the MVAC system.
  • Educate building staff about IAQ management by providing training opportunities.
  • Communicate with tenants and occupants about their roles in maintaining good IAQ.
  • Establish clear procedures for responding to indoor air-related complaints.

For details, please refer to the booklet on “Improve the Indoor Air Quality in Your Building” published by EPD.

11. How can we improve the IAQ in our homes?

The primary cause of indoor air pollution in our homes is the emission of polluting gases and particles indoors. Inadequate ventilation can further increase the level of indoor air pollutant. A humid environment can also increase the levels of biological pollutants like bacteria and fungi. Other sources include burning gas stoves, tobacco smoking, and use of aerosol consumer products containing volatile organic compounds.

In order to dilute the levels of air pollutants, sufficient ventilation should be maintained. Open the windows as often as practicable to promote natural ventilation. Set the fresh air intake correctly and clean the filters regularly when using air-conditioners. Use exhaust fans in kitchens and bathrooms. Quit smoking for your own health and your family. Also, keep the home clean and dry.

For details, please refer to the booklet on “Improve the Indoor Air Quality in Your Home” published by the EPD.

12. How do we know which types of carpet, cushion, or adhesive are IAQ-friendly materials?

Look for and purchase carpet, cushion, or floor-covering adhesive with green label, e.g. the label developed by the Carpet and Rug Institute (CRI) in collaboration with USEPA. This labelling programme identifies the products that have been tested and met stringent IAQ requirements for very low emissions. The labelling programme covers carpet, carpet cushion, and floor covering installation adhesives.

13. What furniture should we choose to improve IAQ?

Do not replace old furniture unless absolutely necessary. Select furniture made of low-formaldehyde wood panels meeting European E1 standard, China GB18580-2017, the Japan F-Two Star, or similar standards.

For details, please refer to the leaflet on “New Furniture and Indoor Air Quality” published by EPD. 

14. How does low emission office equipment help improve the IAQ?

Low emission office equipment can reduce the contribution of indoor air pollutants such as ozone, dust and total volatile organic compounds to the office, and reduce the impact to the human health.

15. What types of air cleaners are on the market?

There are various types of air cleaners on the market, which include ion generators, ozone generators, mechanical filter air cleaners, and electronic air cleaners. Some air cleaners are combination of the above, utilising two or more such techniques for the removal of indoor air pollutants.

16. Can air cleaner improve IAQ?

Generally speaking, air cleaner should not be regarded as a single solution to IAQ problems, but can be useful to help improve IAQ in conjunction with effective source control and adequate ventilation. Air cleaning alone cannot adequately remove all pollutants typically found in indoor air. Furthermore, the effectiveness of air cleaners to improve IAQ depends on a number of factors including the choice of the right air cleaners and its proper installation, operation, and maintenance.

17. Can plants control indoor air pollution?

The ability of plants to control indoor air pollution has not been well established. While some decorative plants may be aesthetically pleasing, overdamp planter soil conditions may promote growth of unhealthy microbes. Also, some strongly smelling flowering plants may cause hay fever to allergic individuals. As a practical means of pollution control, the ability of plants to actually improve IAQ is thus limited in comparison with provision of adequate ventilation and source control.

18. Can negative ions help improve IAQ?

Negative ions are defined by the US Environmental Protection Agency and Canada National Research Council as atoms, molecules, or particles that carry negative charge. They may be generated in outdoor environment under fine weather in mountains, near waterfalls or seashore. In indoor environment, they can be produced by negative ion generators via ultraviolet lamp or high-voltage corona discharge. 

Negative ions may help remove airborne positively-charged dust particles through attraction, rendering them too heavy to remain airborne. Some studies also showed that negative ions may be beneficial to patients suffering from respiratory diseases and producing some soothing feeling in some cases. While the use of negative ions may help improve IAQ in certain situations, it may cause staining problem since the dust particles deposited may tarnish wall or furniture surfaces. Also, other indoor air pollutants such as ozone may be produced if the negative ion generators are not properly operated and maintained.

19. How can I prevent mould growth?

The most effective way to control indoor mould growth is to keep the place dry and control dust accumulation. Water leakage/seepage problem should be fixed promptly and the moulds should be cleaned once they are found. For details, please refer to leaflet on “Indoor Mould and You”, or booklet on “A Guide on Prevention and Control of Indoor Mould” published by EPD.

20. How should I cleanup mould?

Following are some general tips to clean up the moulds:

  • Protect yourself from the mould and mould spores by wearing disposable mask (e.g. N-95 mask), rubber gloves and safety goggles, and wash hands immediately after the cleanup work.
  • Keep sensitive individuals (such as those with asthma and allergy problem) away from the mouldy area being cleaned when necessary.
  • For moulds on hard surfaces or non-porous materials, wash them with cleaning detergent and water, then dry them thoroughly.
  • Biocides or disinfectants are not recommended due to its potential toxic effect on individuals.
  • Prevent dust generation during cleanup, e.g. gently misting mould-damaged wallpaper with dilute soap or detergent solution prior to removal.
  • For moulds on absorbent and porous materials (e.g. ceiling tiles and carpet) that cannot be cleaned, discard them in a sealed plastic bag, then clean the outside of the bag, remove it from the mouldy area, then tie it in another plastic bag for disposal.

If necessary, you may seek advice from professionals or engage a competent person for the cleanup.

IAQ Management Programme

21. What are IAQ Objectives?

A set of 2-level IAQ Objectives is established to act as the benchmark for evaluating and assessing IAQ are set under the IAQ Certification Scheme. These objectives are comparable to the international health-based air quality standards and can encourage building owners to aim at the best IAQ. They are classified as follows:

“Excellent” Class – represents an excellent IAQ that a high-class and comfortable building should have.

“Good” Class – represents the IAQ that provides protection to the public at large including the young and the aged.

These objectives are mainly based on health-based air quality standards such as the WHO which are intended to protect a more diverse target population including the young and the aged.

The IAQ Objectives are designed for the IAQ inside the entire building and are applicable for all occupants inside the buildings. The rationale of providing different objectives is to minimise the cost of implementation for the achievement of different degrees of the desired “optimal health”. The IAQ Objectives are not meant to be exhaustive to avoid all IAQ problems. However, if all the parameters are met, the likelihood of indoor air pollution leading to health problems or discomfort in the building is remote. Building owners and employers therefore should endeavour to achieve the IAQ Objectives as far as practicable. 

In light of the IAQ guidelines published by the World Health Organization in 2009 and 2010 respectively on dampness and mould, and selected pollutants (viz. HCHO, radon, CO, NO2, benzene, naphthalene, polycyclic aromatic hydrocarbons (PAHs), trichloroethylene and tetrachloroethylene), EPD has completed a review of the prevailing IAQ Objectives adopted since 2003 under the IAQ Certification Scheme to update the IAQ Objectives. The new IAQ Objectives, including a new parameter of mould are effective starting from 1 July 2019. 

A summary of the updates of the IAQ Objectives can be found here.

22. What is the purpose of the “Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places”?

The primary objective of this Guidance Notes (GN) is to give background information and practical guidelines to enable users to prevent IAQ problems, and to solve problems promptly if they arise.

The GN applies to all buildings or enclosed areas served with mechanical ventilation and air conditioning (MVAC) system for human comfort except:

  • domestic buildings
  • medical buildings
  • industrial buildings
  • any area or any part of the building which is constructed, used or intended to be used for domestic, medical or industrial purposes.

This GN does not apply to any part of a building which is enclosed but not served by MVAC system such as store rooms, plant rooms and switch rooms.

This GN also does not cover underground or multi-storey carparks, tunnels, public transport interchanges, public transport facilities, or other partially enclosed areas. However, professional practice notes have been issued for some of these facilities/buildings by the Environmental Protection Department. Guidelines for managing air quality in air-conditioned public transport facilities in respect of buses and railways in the form of professional practice notes were issued in 2003, whereas the practice note for ferry was issued in 2015.

23. What is “Indoor Air Quality Certification Scheme”?

To improve the IAQ and promote public awareness of the importance of IAQ, we have implemented an IAQ Management Programme. One of the core tasks of the Programme is to launch a voluntary IAQ Certification Scheme for Offices and Public Places (hereafter refers as “Certification Scheme”).

The IAQ Certification Scheme for Offices and Public Places (the Certification Scheme) aims to:

  • recognise good IAQ management practices; and
  • provide incentives for owners of premises/buildings or property management companies to pursue the best level of IAQ.

For details, please visit the webpage.