Frequently Asked Questions
(A) Indoor Air Pollution
(B) Health Effects of Indoor Air Pollution
(C) Mitigation Measures to Improve Indoor Air Quality
(D) Indoor Air Quality Management Programme
(E) IAQ Information Centre
(B) Health Effects of Indoor Air Pollution
(C) Mitigation Measures to Improve Indoor Air Quality
(D) Indoor Air Quality Management Programme
(A) 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.
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).
(B) Health Effects of Indoor Air Pollution
Health
effects due to poor indoor air quality may include immediate effects and
chronic effects:
Immediate effects
Immediate effects may include irritation of the eyes, nose, and throat,
headaches, dizziness, and fatigue after exposure to high concentrations
of indoor air pollutants. Such immediate effects are usually short-term
and treatable. Symptoms of some diseases, including asthma, hypersensitivity
pneumonitis, and humidifier fever, may also show up soon after exposure
to some indoor air pollutants.
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.
The term "sick building syndrome" (SBS) is used to describe situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified. Building occupants complain of symptoms associated with acute discomfort, e.g., headache, eye, nose, or throat irritation, dry cough, dry or itchy skin, dizziness and nausea, difficulty in concentrating, fatigue, and sensitivity to odors. The cause of the symptoms is not known and most of the complainants report relief soon after leaving the building.
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.
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 suspected
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.
For details, please refer to the documents IAQ leaflet entitled "Formaldehyde
and You".
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".
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 20oC to 45oC, 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 of Legionnaires' disease, please refer to the leaflet entitled "Understanding Legionnaires' Disease and Its Prevention" published by the Electrical and Mechanical Services Department.
(C) Mitigation Measures to Improve Indoor Air Quality
We
can contribute to improving the IAQ of our air-conditioned buildings. Here
are something you can do:
a. Maintain adequate air ventilation. Do not block air vents and ducts.
b. Do not smoke inside indoor environment.
c. Report to building management in case of water leakage to avoid the growth
of micro-organisms.
d. Dispose of perishable food products properly to avoid generating unpleasant
odour.
e. Report to building management for indoor air quality problems.
If you are an office manager, you can do the followings to improve IAQ:
a. Cooperate and work closely with the building management.
b. Make sure proper air ventilation inside the office.
c. Promote a non-smoking policy
d. Provide a separate ventilation system for pollutants-generating equipment.
e. Replace carpet, false ceiling, etc when odour, water marks and even moldy
marks are detected.
If you are a property manager, you can do the following to improve IAQ:
a. Appoint an IAQ manager who serves as the contact for indoor environmental
issues.
b. Arrange a scheduled cleaning and maintenance programme for the MVAC system.
c. Educate building staff about IAQ management by providing training opportunities.
d. Communicate with tenants and occupants about their roles in maintaining
good IAQ.
e. 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 Home" published by EPD.
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.
For more information, please read the booklet on "Improve
the Indoor Air Quality in Your Home" published by the EPD.
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 indoor air quality requirements for very low emissions. The labelling programme covers carpet, carpet cushion, and floor covering installation adhesives.
You should choose furniture that have low emission of formaldehyde. Furniture made of solid hardwood is preferable. Alternative choices are solid softwood or softwood plywood coated with low-toxicity sealant to retard the emissions from the manufactured wood products. All exposed edges and surfaces should be thoroughly sealed.
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. For details, Table 4-1 in the "Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places" recommends the emission rates for office equipment.
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.
Generally speaking, air cleaner should not be regarded as a single solution to indoor air quality problems, but can be useful to help improve indoor air quality 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 indoor air quality depends on a number of factors including the choice of the right air cleaners and its proper installation, operation, and maintenance.
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 indoor air quality is thus limited in comparison with provision of adequate ventilation and source control.
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 indoor air quality 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.
(D) Indoor Air Quality Management Programme
A set of 2-level IAQ objectives is established to act as the benchmark for evaluating and assessing indoor air quality. These objectives are comparable to the international health-based air quality standards and can encourage building owners to aim at the best indoor air quality. They are classified as follows:
“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.
Table 1 sets out the 2-level IAQ objectives. The IAQ parameters selected for IAQ objectives include room temperature, relative humidity, air movement, carbon dioxide, total volatile organic compounds, respirable suspended particulates, carbon monoxide, nitrogen dioxide, ozone, formaldehyde, radon, and total airborne bacteria. Table 2 also sets out the recommended objectives for individual volatile organic compounds, which serve as an alternative option for TVOC compliance checking for Good Class objective only (see para.3.5.4.9 of the Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places). Nicotine is not included into the IAQ objectives list because respirable suspended particulates to certain extent can be used as an indicator for smoking. We will include an additional parameter, airborne fungi with an indicative level of 500 cfu/m3, for both “Good” and “Excellent” Classes in the next review for the IAQ Certification Scheme.
Table 1: IAQ Objectives for Office Buildings and Public Places
| Parameter | Unit | 8-hour average a | |
| Excellent Class | Good Class | ||
| Room Temperature | ° C | 20 to < 25.5 b | < 25.5 b |
| Relative Humidity | % | 40 to < 70 c | < 70 |
| Air movement | m/s | < 0.2 | < 0.3 |
| Carbon Dioxide (CO2) | ppmv | < 800 d | < 1,000 e |
| Carbon Monoxide (CO) | μg/m3 | < 2,000 f | < 10,000 g |
| ppmv | < 1.7 | < 8.7 | |
| Respirable Suspended Particulates (PM10) | μg/m3 | < 20 f | < 180 h |
| Nitrogen Dioxide (NO2) | μg/m3 | < 40 g | < 150 h |
| ppbv | < 21 | < 80 | |
| Ozone (O3) | μg/m3 | < 50 f | < 120 g |
| ppbv | < 25 | < 61 | |
| Formaldehyde (HCHO) | μg/m3 | < 30 f | < 100 f, g |
| ppbv | < 24 | < 81 | |
| Total Volatile Organic Compounds (TVOC) | μg/m3 | < 200 f | < 600 f |
| ppbv | < 87 | < 261 | |
| Radon (Rn) | Bq/m3 | < 150 i | < 200 f |
| Airborne Bacteria | cfu/m3 | < 500 j, k | < 1,000 j, k |
Legends:
Table
2: IAQ Objectives for Individual VOCs
(for Good Class TVOC Objective Only)
| Compound | Good Class | ||
| ppbv | μg/m3 | Legends: | |
| Benzene | 5
ppbv a |
(16.1 μg/m3) | .WHO (1995), Updating & Revision of the Indoor Air Quality Guidelines for Europe |
| Carbon tetrachloride | 16
ppbv b |
(103 μg/m3) | 1/300 of ACGIH TLV-TWA, ACGIH (1996), ACGIH Threshold Limit Values for Chemical Substances in the Work Environment. |
| Chloroform | 33
ppbv b |
(163 μg/m3) | 1/300 of ACGIH TLV-TWA, ACGIH (1996), ACGIH Threshold Limit Values for Chemical Substances in the Work Environment. |
| 1,2-Dichlorobenzene | 83
ppbv c |
(500 μg/m3) | A continuous exposure guideline value as recommended by WHO |
| 1,4-Dichlorobenzene | 33
ppbv c |
(200 μg/m3) | A continuous exposure guideline value as recommended by WHO |
| Ethylbenzene | 333
ppbv c |
(1,447 μg/m3) | A continuous exposure guideline value as recommended by WHO |
| Tetrachloroethylene | 37
ppbv a,c |
(250 μg/m3) | WHO
(1995), Updating & Revision of the Indoor Air Quality Guidelines for Europe A continuous exposure guideline value as recommended by WHO |
| Toluene | 290
ppbv a |
(1,092 μg/m3) | .WHO
(1995), Updating & Revision of the Indoor Air Quality Guidelines for Europe |
| Trichloroethylene | 143
ppbv a,d |
(770 μg/m3) | WHO
(1995), Updating & Revision of the Indoor Air Quality Guidelines for Europe The Royal Society, London (1983) “Risk level where very few would consider action necessary, unless clear causal risk with consumer products” |
| Xylene (o-, m-, p-isomers) | 333
ppbv e |
(1,447 μg/m3) | Labour Department (2002), Code of Practice on Control of Air Impurities (Chemical Substances) in the Workplace |
Note: All conversion calculations are based on data from NIST Standard Reference Database 69 – March 2003 Release: NIST Chemistry Webbook.
Application
The primary objective of this Guidance Notes (GN) is to give background information and practical guidelines to enable users to prevent indoor air quality problems, and to solve problems promptly if they arise.
The GN applies to all buildings or totally enclosed areas served with mechanical ventilation and air conditioning (MVAC) system for human comfort except:
This GN does not apply to any part of a building which is totally 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 buildings by the Environmental Protection Department (see Part II of Appendix A of the Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places ). Guidelines for managing air quality in air-conditioned public transport facilities in respect of buses and railways in the form of professional practice notes will be issued in 2003. The relevant guideline in respect of ferry is being finalised.
Definitions
“mechanical ventilation and air conditioning (MVAC) system” means the equipment, distribution network and terminal that provide, either collectively or individually, the processes of heating, cooling, humidification, dehumidification, ventilation or air-purification or any other associated processes to a conditioned space except window-type air-conditioners or split-type air-conditioners.
“domestic building” means a building constructed, used or intended to be used for habitation but excluding the use of it for a hotel, guest-house, boarding-house, hostel, dormitory or similar accommodation and the expression “domestic purposes” is construed accordingly.
“industrial building” means
“medical building” means a building constructed, used or intended to be used as clinic, infirmary or hospital and the expression of “medical purposes” is construed accordingly.
“buildings” means buildings and premises.
Scope
The GN should be used as a general guidance document in:
The GN is not a ventilation standard or a detailed manual for assessing indoor air pollutants. Detailed designs are also outside the scope of this GN. However, references to standards for specific designs are provided where applicable. This GN provides guidelines on the indoor air quality objectives for different levels of comfort and optimal health required for offices and public places. In this way building owners and managers can, with advice from relevant experts, select the objective most appropriate to the needs of the occupants, and minimise the costs of implementation.
This GN should be used in conjunction with acceptable guidelines for ventilation such as the latest version of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 62, Ventilation for Acceptable Indoor Air Quality.
Apart from the GN, the Indoor Air Quality Management Group has launched a voluntary IAQ Certification Scheme for Offices and Public Places. Please refer to “A Guide on IAQ Certification Scheme for Offices and Public Places” for details.
To improve the indoor air quality (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:
Key features of the Certification Scheme are -
The purposes of the IAQ Certification Scheme are to encourage the public to actively improve IAO and to promote the importance of IAQ. The Certification Scheme welcomes registration applications for the public areas served by mechanical ventilation and air conditioning (MVAC) system within domestic buildings/premises, for example foyers, clubhouses, etc. For enquiries, please contact the IAQ Information Centre at 2788 6177 or fax to 2788 6181.
For further enquiries related to IAQ issues or the IAQ certification scheme,
please visit the IAQ Information Centre of the Environmental Protection
Department at:
1/F, HKPC Building
78 Tat Chee Avenue,
Kowloon Tong
Kowloon
Telephone : 2788 6177
Fax : 2788 6181
Email : enquiry@iaq.gov.hk
(E) IAQ Information Center
The paints used in the Centre contains the best available refined ingredients, which eliminate the residual toxic chemicals found in typical paints. They avoid extenders, drying agents, formaldehyde, and unnecessary chemical additives. In addition, it helps prevent outgassing from hazardous chemicals contained in previously used coatings or building materials. All such paints can be cleaned up easily with water. They are available in variety of finishes and can be tinted to virtually any colour.
Adhesives, like paints, are either solvent-based or water-based. Solvent-based adhesives contain synthetic resins and solvents that may be environmentally hazardous. On the contrary, water-based, latex adhesives are more environmentally friendly because they contain only small quantities of solvents, and can be cleaned up with water. The adhesive used throughout the Center is a low-odour, non-toxic, water-based adhesive designed for wall and floor tiles, and contains no formaldehyde.
Some carpets and adhesives can offgas for years, that may cause health risks, including headaches, allergies and respiratory problems. Carpets can also be breeding grounds for molds, bacteria and dust mites, which may cause severe allergic reactions. In addition, most carpets are made of synthetic fibers from petroleum sources, which are neither renewable nor biodegradable.
The carpet used in the IAQ Information Centre is made of low emission material and has obtained a green label from the US Carpet and Rug Institute. The product is applied to the floor using dry adhesives, thereby avoiding the offgasses associated with traditional wet adhesives. The carpet's cushion is free from harmful CFC's or HCFC's.
Most household cleaning products give out emissions. The cleaning product used in the Centre is a non-toxic, odour free, dye free and biodegradable cleaner/degreaser. It contains no phosphates, alkaline, acids, ammonia, butyl ethers, chlorine bleach, nor any chemical scents used to mask the odours. It will not irritate sensitive skin, nor will it give off noxious fumes.
Medium density fibreboard (MDF) is produced by combining wood pieces and chips with urea-formaldehyde adhesives and pressing it together in hot hydraulic presses. Instead of from the wood product itself, the irritating emission (i.e. formaldehyde) actually emanates from the urea-formaldehyde adhesives that hold together the pieces of wood. Manufacturers of MDF use formaldehyde adhesive because of their excellent bonding properties.
The MDF used in the IAQ Information Centre is different from the conventional MDF in that the adhesives which are used to glue together the wood pieces and chips are formaldehyde-free synthetic resin, thus minimising the emission of formaldehyde from the MDF. Moreover, the MDF used in the Centre is more environmentally friendly as it is manufactured mainly from recycled wood, which includes residuals from primary wood products, and non-commercial wood scrap.
The IAQ Information Centre is equipped with a photocatalytic oxidation (PCO) system to reduce the level of bacteria and fungi. PCO utilises titanium dioxide (TiO2) and ultraviolet light to kill bacteria and fungi. It works under the principle that when TiO2 is illuminated by UV light, electrons in the valence band are excited to the conduction band leaving behind positive holes (h+). These positive holes react with hydroxyl groups (OH-) in water vapour adsorbed on the surface of TiO2 resulting in the formation of hydroxyl radicals (OH.). These highly reactive radicals can oxidize most VOCs under ambient condition, thus decomposing them into harmless carbon dioxide and hydrogen that is released into the air. Germs at indoor environment will also be destroyed by the above mechanisms.
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