Indoor Air Quality, Sick Building Syndrome, Building Related Sickness and Environmental Health has been associated to the dampness in buildings. Mold Outbreaks have been common worldwide and microbial infections have been a public concern since the 1990s. Many government agencies and voluntary bodies in America like the Environmental Protection Agency (“EPA”), New York City Department of Health (NYCDOH), Centre for Disease Control and Prevention (“CDC”), Institute of Medicine (“IOM”), American Conference of Industrial Hygienists (“ACGIH”), Institute of Inspection, Cleaning, Remediation Certification (“IICRC”), International Society of Indoor Air Quality and Climate (“ISIAQ”) and America Industrial Hygienists Association (“AIHA”) have published various guidelines in Mold, Mold Prevention and Remediation. In addition, World Health Organization (“WHO”) in Europe have published “WHO Guidelines for Indoor Air Quality: Dampness and Mould” in 2009 in recognition for the seriousness of Microbial Growth due to Dampness in Buildings as a public health concern globally.
All of these agencies and bodies regard visible indoor molds is not tolerable to the health in consensus . This view is supported by abundance of researches and scientific publications. Visible mould was positively associated with asthma, wheeze and allergic rhinitis. According to CDC, children in homes with visible mold are 49 percent more likely to have asthma than kids not exposed to the problem. In addition, the risk of nasal allergies is 39 percent higher among children in the moldy houses, too.
The objective of this paper is to review the various guidelines from these agencies, including the mold prevention strategies and mold remediation cleaning procedures with consideration local climates, building materials and practices. In addition, review will be made on the researches conducted in this topic in Malaysia so that a more holistic review and recommendation can be made.
Climate and Ecology in Malaysia
We live in the tropical area with abundant of rainfall and sunshine throughout the year. The average rain fall is as high as 2500mm per annum and the average temperature is 27 degree Celsius. Vast variety of fauna and flora thrives in our thick tropical rain forests. In general, the ambient humidity is high, ranging from above 60% Relative Humidity (“RH”)  in the day time to approx 100% at night in the outdoor environment. The rich and moist soil in the forests with plenty of organic food in the top soil offer heavenly conditions for growth and it houses huge diversity of organisms, ranging from the visible insects, termites and reptiles to the microscopic organisms which are not visible to the naked eyes.
These microorganisms play an important role to decompose dead plants and animals and replenish the nutrients to the mother nature, contributing to the chemical balance in the ecosystems. Microorganisms are microscopic organisms and there are present naturally in our habitats and bodies. In fact, they are used in the fermentation of alcohol, making of cheese, production of Antibiotic, power generation (methane gas) and water treatment. With the rapid development in genetic engineering and biotechnology, microorganisms will continue to benefit us.
In comparison to the hot and humid weather in the outdoor, the relative humidity in the indoor environment ranges within 60% to 70% RH in our buildings. However, in the areas with higher dampness like the toilets, kitchens, non-shaded external walls, on the drains and laundry areas, the Relative Humidity is higher. Black, yellowish, green or brown circular spots can be easily found in these places. In addition, these circular spots can be found on leaky ceilings and they are commonly regarded them as common and negligible” stains” in Malaysia.
Prof. Dr. Vikineswary Sabaratnam, a prominent Microbiologist in Universiti Malaya conducted research on these “stains” with collection of samples on the external walls throughout Malaysia and she isolated more than 100 type of microorganisms from the samples. These include mold, bacteria, viruses, algae, protozoa and microscopic animals, mites and plants. Although majority of microorganisms are harmless, some of them are health hazardous pathogens.
Indoor Microbial Growth and Environmental Health
Despite the diversity of the microorganisms, they germinate, replicate and thrive in the condition as follows:
1) Humid condition, with Relative Humidity above 70 percent adjacent to surfaces
2) Availability of food
3) Oxygen (Some microorganisms are anaerobes)
4) Temperature (20 degree Celsius to 45 degree Celsius)
Non- availability of any of the above conditions can prohibit the growth of microorganisms.
Indoor environments normally contain settled fungal spores, airborne bacteria and other microorganisms awaiting for the hospitable condition for growth. Nutrient are readily available on the fibrous and cellulose materials like upholstered and wooden furniture, plywood, chipboards, MDF boards, paint, food waste, sheded skin etc.. The normal indoor oxygen level and temperature (29 degree Celsius to 34 degree Celsius) are rather conducive for the growth of microorganism. As a result, moisture level becomes the determining condition in the growth of microorganisms. Thus, water damaged buildings are associated to microbial growth with potential health risks for infection through respiratory tracks.
As most Malaysians spent approximately 90 percent of their time in the buildings, excessive presence of microorganisms in the buildings lead to exposure of the occupants to bacteria and mold level which is not tolerable to the healthy adults. Some species of Bacteria and Mold can produce spores and/or endoscope. Beside, some of these microorganisms produce enzymes that caused decay on the building materials which adversely affect the structural integrity and authenticity of the buildings. Unpleasant musty odour produced can jeopardize the comfort of the occupant, too.
Healthy adults have immunity that can resist pathogenic airborne microorganisms with total bacteria count of up to 500 CFU/m3 and total fungal count of 1,000 CFU/m3, according to the Industry Code of Practice for Indoor Air Quality 2010 in Malaysia and America Conference of Industrial Hygienists’ Mold Guidelines. However, the young, old, sick and pregnant have lower immunity and they are more susceptible to the invasion of these airborne pathogens.
A comprehensive study was conducted by the Institute of Medicine, USA in the effect of Dampness, Microbial Growth and Health Effect. A report known as “Damp Indoor Spaces and Health” was published in 2004. Appended hereunder is a summary of the findings.
Evidence of Association between Damp Indoor Environments and Mold Health Outcomes
Health outcome or symptom
Exposure to damp indoor environments
Presence of mold/other agents in damp indoor environments
Upper respiratory tract symptoms1
Sufficient evidence of an association7
Sufficient evidence of an association
Sufficient evidence of an association
Asthma symptoms in sensitized persons with asthma
Sufficient evidence of an association
Hypersensitivity pneumonitis3 in susceptible persons
Studied in relation to specific agents
Sufficient evidence of an association
Shortness of breath (dyspnea)2
Limited or suggestive evidence8
Inadequate or insufficient evidence9
Respiratory illness in otherwise healthy children
Limited or suggestive evidence
Respiratory illness in otherwise healthy adults
Inadequate or insufficient evidence
Inadequate or insufficient evidence
No specific studies associated the condition with damp or moldy indoor spaces
Severe respiratory infections in people whose immune system is severely immunocompromised5
Sufficient evidence of an association
Sufficient evidence of an association
Colonization and potential lung infection in people with some chronic pulmonary disorders6
Sufficient evidence of an association
1. Upper respiratory tract symptoms include nasal congestion, rhinitis, allergic rhinitis “hay fever", sneezing, runny or itchy nose, sinusitis and sore throat.
2. Lower respiratory tract symptoms include cough with or without production of phlegm, wheeze, chest tightness, and shortness of breath.
3. Hypersensitivity pneumonitis is a lung disease that is the result of exposure and sensitization to antigens inhaled with a variety of organic dusts. Symptoms include dry cough, dyspnea, and fever and sometimes acute bronchospasm.
4. Fungal sinusitis is associated with molds but molds may come from the indoor or the outdoor environment.
5. Immunocompromised persons are at increased risk for fungal colonization or opportunistic infections.
o It is well established that fungal exposures causes opportunistic cutaneous and subcutaneous fungal infections of the skin of severely immunocompromised persons.
o Respiratory infections can result from exposure to fungi, including Aspergillus spp. and Fusarium spp.
o Severely immunocompromised persons include persons who undergo high-dose cancer chemotherapy, are recent recipients of a solid-organ transplant, or are otherwise immunocompromised.
6. Chronic pulmonary disorders include cystic fibrosis, asthma, and COPD. Colonization and infections result from exposure to fungi such as Aspergillus.
7. "Sufficient evidence of an association" means that studies show an association between the agent and disease and chance, bias, and confounding were ruled out with reasonable confidence.
8. "Limited or suggestive evidence of an association" means that evidence is suggestive of an association between the agent and the disease but is limited because chance, bias, and confounding cannot be ruled out with confidence.
9. "Inadequate or insufficient evidence to determine whether an association exists" means that the available studies are of insufficient quality, consistency, or statistical power to permit a conclusion regarding the presence of an association. Alternatively, no studies exist that examine the relationship.
10. Respiratory infections, fungus-related illnesses, and colonization with lung infection relating to specific organisms.
Source: Institute of Medicine’s "Damp Indoor Spaces and Health" (http://www.nap.edu/books/0309091934/html/).
There are a few implications in this report. Firstly, damp indoor spaces attract dust mites, termites, insects, cockroaches and rodents (rats and mice). Dust mites, fragments and dropping from the cockroaches are highly infectious allergens which can cause our bodies to develop allergenic reactions against them. Furthermore, microbial growth induced by indoor dampness is associated to allergy and infection at the respiratory tracts and skins among the people with impaired, deteriorating or under-developed immune system. Some metabolites of the microorganism are carcinogenic and toxic. Prolonged exposure to these metabolites can cause disordered immune system and chronic respiratory illness. Thus, prevention of indoor dampness is the key in maintaining Indoor Air Quality and Environmental Health in the long run.
Airborne Bacteria (Indoor)
Bacteria make up the biggest biomass on earth and readily available in the soil, water and air. Although majority of Bacteria are not hazardous and health threatening, some of them are pathogenic and they can cause acute sicknesses. They are group of microscopic single cell organisms whose do not have true nucleus, or any other membrane-bound organelles. They do have one chromosome of double-stranded DNA in a ring and they reproduce by binary fission, a self expansion and asexual division of cell for reproduction.
Some scholars in local higher tertiary education centres like University Malaysia Terrengganu have conducted some indoor air quality assessment in the university in 2011 and found out that Legionella pneumophila is a dangerous bacterium that can be found in poorly maintained Air Conditioner Systems and it has become main cause of fatal Pneumonia and Moraxella Catarrhalis infection . These bacteria can attach to the mist of contaminated water and infect us at the respiratory tracts. Other genus of Legionella can cause Pontiac fever, high fever, chill, cough, muscle pain and headache, without pneumonia infection .
In addition, a study by a group of scientists in University Putra Malaysia in five randomly selected primary schools in Malaysia in 2011 found that normal flora bacteria was the most frequently isolated bacteria including Staphylococcus spp., Pseudomonas spp., Bacillus spp. and Terribacillus spp.. The average concentrations of bacteria in indoor and outdoor air were 1025 ± 612 CFU/m3 and 1473 ± 1261 CFU/m3, respectively . Except Staphylococcus spp, all these bacteria are pathogenic.
In a study supported by Sweden Council for Environmental and Agriculture Science and Spatial Planning which involve 8 secondary schools in Johore in 2010, a genus of bacteria known as Streptomyces spp was detected in most of their samples was a risk factor for doctor-diagnosed asthma in these schools. This bacterium causes mycetoma (chronic subcutaneous infection) and inflammation to the respiratory tracts. In some serious cases, invasion of Streptomyces to the bloodstream was reported .
In comparison to the acceptable total bacteria count of 500 CFU/m3 in indoor environment, bacterial infection is a common threat to the pupils in Malaysia.
Molds are microfungi with microscopic structures. In hospitable environment for growth, microscopic seeds like structure known as spores absorb water, swell to 2 to 3 times their original size, and begin to form thread-like structures known as hyphae. As hyphae grow, root like structure known as mycelium grow and penetrate deep into the food source in search for more nutrients. Emission of enzyme assists breaking down of organic food into simple nutrients. A tangled mass of hyphae visible to the unaided eye is a mycelium. When mycelium continues to grow in all directions, a circular pattern will be formed. When the mold mature, aerial hyphae will form and release spores in their reproduction process.
Spores of different genera and species of mold take different duration for germination. In general, Molds start to grow on damp spots with hospitable environment if the dampness last for more than 24 hours.
Many molds that thrive in damp indoor environments produce Mycotoxin and Microbial Volatile Organic Compounds (“mVOC”) which is linked to moldy musty odour. Some of these mycotoxin and mVOCs are carcinogenic and/or toxic. In poorly ventilated indoor environments, the concentration of these toxins in the indoor air increase overtime, causing the consequential drop in Indoor Air Quality. Inhalation of these toxins can cause toxic effects ranging from short-term irritation to immunosuppression, severe dermatosis on the skins and cancer .
In addition, inhalation of excessive spores and mold fragments can cause the immune systems to overreact to these allergens. This reaction triggers a cascade of reactions that lead to allergy symptoms. Like other allergies, a mold allergy can make you cough, make your eyes itch and cause other symptoms that make you miserable. In some people, mold allergy is linked to asthma and exposure causes restricted breathing and other airway symptoms. Continuous exposure to these biology pollutants like bacteria and mold spores, fragments and metabolites (Mycotoxin and mVOCs) can cause weakening in the immune systems due to the toxic effects and development of allergy, resulting in opportunistic infections.
There are numerous guidelines of biological pollutants in USA and Europe. Amongst the most hazardous indoor molds that give rise to public health concern in these countries include Strachybotrys Chartarum, Aspergillus Versicolor, Penicilium, Chactomium, Trichoderma, Phoma, Fusarium, Trichothecenes, A. Flavus, A. Fumigatus, Fusarium Moniliforme and Histoplasma Capsulatum. Upon verification with Prof. Dr. Vikineswary Sabaratnam of Universiti Malaya, all these molds are present in Malaysia.
In the study conducted by a group of scientists in University Putra Malaysia in 5 primary schools in 2011, the most frequently isolated fungal genera in these primary schools were Aspergillus, Penicillium, Fusarium, Rhizopus and Zygomycetes with the average concentration of fungal bioaerosol in indoor and outdoor air were 292 ± 83 CFU/m3 and 401 ± 235 CFU/m3. All these molds are pathogenic parasites.
In the research by the Swedish scientists that targeted the study of the association of Asthma to fungal DNA, allergens and mycotoxins in secondary school in Johore conducted in the year 2011, scientists found fungi level were high enough and mycotoxins have been detected in up to 22 percent of classes involved in the study. The total fungal DNA levels were 50 times higher than a Swedish day-care centre study, using the same sampling method conducted in Sweden. This is attributed by the hot and humid climate conditions in Malaysia which is conducive for microbial growth. It was concluded that fungal DNA and cat allergens were common in the studied Malaysian schools and there was high prevalence of both doctor diagnosed asthma and respiratory symptoms among the students.
Prevention of Microbial Growth - Moisture Control
The climates, buildings and men form a microecology where they interact with each other within the buildings. For instance, climate influence the Relative Humidity in the indoor environment and we design our buildings to create a hospitable environment with comfortable humidity level and shelter us from the rain and ground water. Nevertheless, our activities like breathing, cooking, washing and showering increase the Indoor Relative Humidity. Vapor produced by our activities is vented through the windows or driven out of the buildings by mechanical means like the exhaust fans. Waste water is channeled to the drainage system and dampproofing system installed prevents water seepage to the floor and soaking of water to the wall via capillary suction.
Rain Penetration and Ground Water
The hot and humid climate with an average rainfall of 2,500mm per annum, high Relative Humidity and vast coverage of forest and landscaped areas posses a big challenge in Moisture Control and Mold Prevention in Malaysia. The increase in rainfall, thunder storms and floods recently has been observed due to the green house effect globally. As a result, Rain Water and Ground Water has become a major concern in the Moisture Control in Malaysia.
The mechanism which prevents rain penetration include the roof system, gutters, flashings, rain water down pipes and the drainage system. The gradient on the slope varies according to the roof system employed. On flat concrete roof, the deterioration of waterproofing membranes, construction joints and expansion joints is caused by ultra violet, thermal pressure difference and movement due to settlement, wind load and mechanical parts installed (i.e. water tanks, cooling towers and gondolas). In addition, poor maintenance and cleaning on the flat roof like debris causes water collection and blockage can expedite the deterioration due to permeation of water, build up of acidity in the concrete and concrete damage due to swelling of reinforcement steel bars due to oxidization. Indeed, they need regular replacement and maintenance in order to upkeep the functionality and performance. On average, these systems require replacement every 10 years.
Besides, sloppy ground with gradient that drain rain water away from the building (i.e. 5% steepness, 6” per 10 ft) is vital to prevent capillary suction of rain water through the foundation and the floor. Waterproofing at the foundation, vapor diffusion retardants below the concrete floor slab and dampproof course on the first layer of bricks are important mechanism to prevent vapor diffusion via capillary suction of the ground water. If the steepness of the earth cannot be altered for proper drainage due to unforeseeable limitation, installation of underground subsoil system can assist prevention of ground water intrusion to the buildings.
Building Construction Authority (“BCA”) in Singapore conducted a survey involving about 10,000 private residential units and found almost 90 percent of water seepage came from the cracks in the plastered external walls. Being a maintenance contractor, the author has evidenced many incidence of this nature in the building in Malaysia. BCA outlines many good industry practices in construction including waterproofing of external perimeter walls and planters, dampproof course, proper method in brick laying and plastering, material handling, installation of mess reinforcement at the bricks and edges, application of sealant and the treatment at joints between dissimilar materials. Although these recommendations are not compulsory in Malaysia, it is good measures that we should consider in improving the construction quality.
Water Consumption and Discharge
Plumbing system requires regular maintenance, too. Steel pipes prone to rust and leak due to the exposure to chlorine in the domestic water. Other piping and sealing materials like PVC, ABS and PE also have an average life of 15 years.
Waterproofing system in the areas with regular wetting and water consumption must be installed according to the systems outlined below. Construction of 25mm X 25mm of angle fillets, application of highly elastic and adhesive waterproofing compound, cement rendering and installation of tiles with the desired gradient (i.e., 1” drop per 10’) must be installed to prevent seepage of waste water via gravity and capillary suction to the adjacent walls. Such system is applicable to the toilets, laundry and kitchen in the ground floor.
Hygroscopic materials and soft wood used in the building also is prone to microbial growth. These products include the fabrics, plywood, chipboards, MDF boards, timber floor, carpet, lumber for roofs and furniture. The moisture content in these materials is above 10 percent. If coupled by a low level of dampness, say 65 percent RH, the air adjacent to these surfaces will reach dew points at the lower temperature at night and they become hospitable to microbial growth.
The hot and humid climate causes vapor diffusion into the building due to the higher vapor pressure in the outdoor environment. Therefore, vapor diffusion retardant is important to prevent such high inward flow of moisture. In areas with low latitude, sealer and coating system on the external walls is commonly adopted due to the ease of application and low costs.
Vapor is also produced during our breathing and daily activities like showering, washing, combustion, cloth drying and cooking. In addition, ornament water features, aquariums, plants and pets contribute to the increase in indoor humidity, too. Ventilation of the vapor produced is vented outdoor with exhaust fans, cooking hoods, vented roof systems and ventilators.
Vapor in the air condense to water when the air can no longer withhold the water in the air when it encounter a surface with a low enough temperature. Condensation of the vapor causes wetting of the surfaces which promote microbial growth.
Due to the hot climate in Malaysia, adoption of air conditioners is common. In residential buildings, split unit air-conditioners are most common. In fully air conditioned residential buildings with fully sealed openings and no dehumidification, moisture control become a big challenge. Although the RH of the chilled air is lower, vapor can diffuse inward from the high RH outdoor air due to non-availability of vapor diffusion retardant, cavity, unplanned openings and excessive ventilation. In addition, non-availability of dehumidified fresh air supply can elevate indoor moisture due to our normal activities, too. Thus, the humid air will condense when it encounters the cold indoor surfaces caused by the air conditioning.
Oversizing and prolong use of air conditioners causes cooling of walls that extends to the external surfaces, depending on the conductivity of the materials used in the construction of the wall and the availability of insulation. Condensation occurs on the external wall when the cold wall surfaces encounter humid external air. In the rigorous environment in the hospitals and cleanrooms, foam or glass wool insulation is needed in preventing condensation.
Sufficient insulation must be installed on the copper tubes for the coolant that connect the indoor blower and the external condenser. Leaking caused by condensation can be evidenced due to insufficient insulation and the wrapping at the joints of the insulation tubes. Double insulation without tightening at the joint of the insulation tubes is recommended.
In commercial building which is air tight with comprehensive and planned mechanical ventilation and cooling system, dehumidifier is integrated in the air handling and fresh air supply system. Positive air pressure relative to the external air is maintained in order to prevent intrusion of humid external air. Air ducts must be sealed with mastic in order to prevent air leakage. In addition, the duct must be covered by sufficient insulation, i.e. foam or glass wool and covered by aluminium foil as vapor diffusion retardant.
Condensation water produced in the cooling system must be effectively drained away with the dripping pan and the piping. This drainage system must be cleaned and maintained regularly in order to prevent any blockage which will cause build-up of stagnant water, hence promoting microbial growth.
The bacteria known as Legionella pneumophila has been identified widely and its growth in the old cooling towers with corrosion and metal sediment in the hot and humid climate . Water treatment and regular monitoring and cleaning of the water quality in the Cooling towers is necessary to prevent the build-up of biofilm amd Legionnaire disease. Routine screening, although not mandatory, is recommended to monitor the Legionella. The American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE) will release ASHRAE Standard 188: Prevention of Legionellosis Associated with Building Water Systems in summer 2012. This standard outlines the proactive preventive measure and the procedures in annual water monitoring, risks analysis, disinfection and recovery plan in the event of Legionnaire outbreak in air conditioning systems and water systems .
Myths in Controlling Biological Contamination and Deodorization
There are a few common myths related to the control and clean-up of biological contamination and deodorization in Malaysia. These are quick fixes that do not address the underlying problem in moisture intrusion that lead the microbial growth. In many instances, these quick fixes create other corresponding adverse side effects when the symptoms of the contamination are covered up.
Ultraviolet Germicidal Irradiation
Ultra Violet Germicidal Irradiation (“UVGI”) that uses low pressure mercury lamp to produce Ultraviolet C (“UVC”) with wavelength of 200nm to 300nm. They are installed in the ducting system or in the portable air cleaners.
UVGI can disrupt the DNA of the microorganisms and render them inactive and harmless to us. Nevertheless, the effectiveness in disinfection depend on the duration of exposure to the radiation, susceptibility of the ultra violet inactivation of different microorganism and their spores (bacterial and fungal spores are the most resistant to UVGI), dust coverage on the UVGI lamps, ability of microorganism to repair their damaged DNA and wear and tear of the UVGI lamps . Ozone gas, an air pollutant, is produced when UVC hits oxygen gas. Besides, the inherent risks of leakage of UVC which is a low penetrating form of UV compared to Ultraviolet A and Ultraviolet B can be detrimental to our eyes. It can cause inflammation to the cornea and retina, including blindness, if not shielded properly. The exposure of skins to the UVC which is mutagenic and carcinogenic can cause skin aging and skin cancer, in some rigorous cases. Since UVC is invisible light, its leakage can hardly be identified .
Ozone comprises of three oxygen atom with unstable molecular bonds and is a strong oxidation agent. Some vendors claim that ozone generators which are sold as Air Cleaner can clean the air via oxidation of organic pollutants including biological contaminants like the bacteria and molds. They also claim that these ozone generators are safe for use and capable of controlling indoor air pollution. Nevertheless, such claim has been refuted by medical professionals .
Concentration of Ozone gas is safe at 0.05ppm. At this level, it has been scientifically proven that it takes too long for the reaction of the oxidation cleaning. Secondly, for many of the chemicals with which ozone does readily react, the reaction can form a variety of harmful or irritating by-products .
Ionizers which is also known as “Electronic Air Cleaners”, are devices that disperses negatively (and/or positively) charged ions into the air. These ions attach to particles in the air giving them a negative (or positive) charge so that the particles may attach to nearby surfaces such as walls or furniture, or attach to one another and settle out of the air. In recent experiments, ionizers were found to be less effective in removing particles of dust, tobacco smoke, pollen or fungal spores than either high efficiency particle filters or electrostatic precipitators .
Photo Catalytic Oxidation
Photo catalytic oxidation (“PCO”) is another oxidization agent which is claimed to be stronger than Ozone Gas in controlling indoor pollutants including microorganisms. Recently, EPA has funded the research and scientifically proven that application of PCO is limited because currently available catalysts are ineffective in destroying gaseous pollutants from indoor air. In addition, oxidation of some chemicals available in indoor environment can produce more harmful by-products that worsen the indoor air quality .
Air filtration in residential and commercial buildings is designed for entrapment of particulate dusts. Depending on the blowing load and filtration efficiency of the filters adopted, the filtration of large particulate dusts can be ineffective for larges dusts which will settle from the air quicker on the ground before it reaches the filters. In rigorous environment with high expectation for cleanliness, High Efficiency Particulate Air (“HEPA”) filters and strong blowing fans are adopted.
In addition, air filtration cannot remove contaminating gases like the mycotoxin and mVOCs produced by molds and bacteria 
Air Duct Cleaning
According to EPA, air duct cleaning has never been showed to prevent health problems. Air duct cleaning is only needed in the event of identification of visible molds inside the ducts or on other component in the air conditioning system, clogging caused by excessive deposition of dusts and/or infestation of vermin (rodents and insects). Normal settled dusts and spores are not harmful.
EPA emphasizes on the importance of settling the underlying problems of these problems before any air duct cleaning. Otherwise, these problems will recur. Indeed, air duct cleaning alone produce limited effect in the improvement of indoor air quality. More emphasis should be given to prevention of the dirt and water from entering the air ducts. Although there is no detrimental effect for engaging air duct cleaning, professionalism and comprehensive cleaning in all air conditioning components is needed for a thorough servicing .
Perfume sprays are widely installed in the offices in order to give some pleasant scent and combat musty odor. Nevertheless, little has been known about the deterioration to the indoor air quality.
Researchers concluded that Perfume-scented strips can cause exacerbations of symptoms and airway obstruction in asthmatic patients. Severe and atopic asthma increases risk of adverse respiratory reactions to perfumes . In some cases, an excessive use of perfumes may cause allergic reactions of the skin. For instance, acetophenone, ethyl acetate and acetone while present in many perfumes, are also known or potential respiratory allergens .
Bacteria and Mold Disinfectants
Bacteria and Mold Disinfectant can effectively kill and remove these microorganisms. However, dead mold fragments and spores are equally allergenic, be it alive or dead. Furthermore, biocides and antimicrobials can be harmful to humans, pet and wildlife if not used properly. These chemicals should only be used to treat microorganisms on the surfaces and structures and in the manner for which the products have been registered by appropriate government agencies.
Anti Microbial Coatings
Anti Microbial Coatings which integrate Nano Silver and other innovative disinfectant chemicals can hardly be applied to some concealed areas that microorganisms grow, i.e. internal part of Gypsum Board Partitions and Insulation, air ducts and wooden roof trusses. These coatings should not be adopted with the tolerance to moisture control.
Cleanliness on the External Walls
Mold grows on the external walls is an indication of a reservoir of microorganisms in close proximity. Water seepage on cracks and cavities on the external give rise to the dampness that is hospitable to microbial growth. Water seepage and air leak in the cavities can bring in the spores and fragments of microorganisms and increase the microbial concentration indoor. The normal breath of wind at 15 to 20 knot can effectively carry the spores into the buildings via the doors, window and other openings.
Decontamination of Microbial Outbreak
Decontamination exercise has been recommended by all the renowned agencies in environmental health and industrial hygiene, including EPA, AIHA, ACGIH, IICRC, NYCDOH, Canada Health Department and ISIAQ. Moisture control and physical removal of visible molds with proper containment, personal protection equipment and disposal of contaminated materials is vital in reducing the contamination, avoiding cross contamination and protecting the workers and occupants.
AIHA has reviewed 7 voluntary remediation guidelines of the above mentioned agencies and 4 mold remediation and assessment documents in its recent publication known as “Recognition, Evaluation and Control of Indoor Mold”. Several principles in mold assessment are common in these guidelines and document as outlined below:
1. Mold growth (colonization) should not be tolerated on indoor materials and furnishing
2. Initial assessment and evaluation should include a thorough visual inspection
3. The extend of mold growth and water damage should be visually assessed
4. Intrusive method of assessment such as use of a borescope or creating openings into closed cavity is necessary to inspect hidden mold
Common principles in remediation of indoor mold include:
1. Moldy building materials and content should be cleaned and discarded
2. Remediation work should be conducted in a manner that limit the mold be aerosolized and limit aerosolized materials in the workplace
3. The type of containment should be guided by how much building materials/ content is impacted
4. The remediation areas should be clean and free from visible mold and debris
5. Small areas of mold can be addressed by building maintenance and engineering staffs
6. Professional judgment should be utilized when there is more than a small area of contamination
Common principles in worker health and safety measures include:
1. Personal Protection Equipment in the form of respiratory protection, gloves and eye protection is recommended
2. Any worker expected to perform remediation work of any size should receive training commensurate to the extend of the expected work to be performed 
Amongst the abundant guidelines and document in mold assessment and remediation, the document published by the IICRC has been accepted by the America National Standard Institute (“ANSI”) as the national standard, namely ANSI/IICRC S520 Standard and Reference Guide for Professional Mold Remediation.
In the event of microbial outbreak, investigators must be protected with sufficient Personal Protection Equipment (“PPE”) in view of the inherent risks of such outbreak. Knowledge in Building Science, Thermodynamics, Materials Science and Medicine is vital in order to earn preliminary understanding of building damage, epidemic response among the occupants and the subsequent remediation plan. In some complicated cases, experts from other disciplines will be invited for a professional diagnosis and planning of procedure and extent of remediation.
Occupant of the affected buildings will be interviewed according to questionnaires. Indoor Air Quality Assessment which involved air sampling and isolation of microorganism is needed in the ambiguous situation.
Diagnostic tool involve in ascertaining the vapor intrusion and generation are appended hereunder:
1. Thermo-hygrometer – a device that measures the temperature and ambient RH
2. Moisture Meter – a probe that measure moisture level on the substrates
3. Psychrometric chart – a chart to determine the Dew Point Condition
4. Manometer – an instrument to measure the static air pressure differential between two or more adjacent areas
5. Thermal Imaging Device – an instrument used to detect surface temperature differences and do not detect moisture or measure moisture through materials
6. Borescope – An optical device allow remote viewing into concealed areas, such as wall cavities, air ducts and the hidden compartment of utilities
7. Data Loggers – this is chart recorders that measure and record atmospheric conditions over time
Other more advance equipment and non-destructive testing for complicated cases include:
1. Pressure Gauge Testing – a device to check the domestic water pipes
2. Echo inspection – an instrument to inspect hidden utilities and cavity
3. ASTM D5957 - 98(2005) Standard Guide for Flood Testing Horizontal Waterproofing Installations
4. ASTM C1060 - 11a Standard Practice for Thermographic Inspection of Insulation Installations in Envelope Cavities of Frame Buildings
5. Ultrasonic Leak Detector – A device that detect underground pipe leaking
6. Blower Door Test – A analytical system for assessment of air leak in the ducting system
After the initial inspection is completed, the next step involves developing a preliminary determination that draw a conclusion on the identification of actual or potential mold growth, known or suspected areas of moisture intrusion and the need for the involvement of other experts or health care professionals.
The investigators need to determine the risk level and a formal assessment of Condition 1, 2 or 3 as follows:
Condition 1 (normal fungal ecology): an indoor environment that may have settled spores, fungal fragments or traces of actual growth who identity, location and quantity are reflective of a normal fungal ecology for a similar indoor environment
Condition 2 (settle spores): an indoor environment that is primarily contaminated with settled spores that were dispersed directly or indirectly from a Condition 3 area, and which may have traces of actual growth
Condition 3 (actual growth): an indoor environment contaminated with the presence of actual mold growth and associated spores. Actual growth includes growth that is active or dormant, visible or hidden.
Upon the determination of the type of Condition and the risk assessment, the investigator can develop work plans, protocols ad specification. Consideration in such remediation procedures include containment, pressure differentials, hazardous or regulated materials, safety and health provisions, contents, contamination materials removal and handling, detail cleaning, disposal, post remediation evaluation, post remediation evaluation and containment removal.
These plans must be communicated to the customers and building occupants before the execution of work. In addition, workers involved must go through medical surveillance check-up before commencing the work. Then, occupants will respiratory illness and mold allergy must be isolated during the course of work.
Remediation commence with the briefing and training to the workers involved with regards to the use of PPE and the scope of work. Then, containment is erected according to the specification and negative air exhaust fans with HEPA filters are installed. Leaking and moisture intrusion must be stopped first. Materials exposed to microbial growth are cleaned with HEPA Vacuum and damp wiping, sanding and scrapping is done, depending on the type of surfaces. Porous materials are physically dismantled, packed with double disposal bags and duly labeled as dangerous hazardous waste. For porous materials with visible mold that need to be preserved, special preservative cleaning and drying is recommended. The debris will then be delivered to designated disposal sites or processed by designated waste management contractors .
In the hot and humid climate in Malaysia, dehumidification with the use of dehumidifiers is critical. Steam cleaning is not recommended due to the excessive humidity released. Use of Disinfectant is not necessary except in the outbreak caused by Bacteria and Viruses. Antimicrobial coatings and sealant can be adopted without the compromise to moisture control. Duct cleaning is no recommended except in the event of identification of visible molds in the ducting and air conditioning systems.
Post remediation Evaluation
Evaluation with Laser Particulate Counters, air sampling and thermal graphic imagers is used after the remediation work. Unless and until the evaluation indicates successful result, the containments will not be taken down and disposed.
Conclusion and Recommendation
The hot and humid climate in Malaysia is indeed a heaven for microorganisms. Any moisture intrusion can easily give rise to microbial growth. Although limited, the scientific publications available in Malaysia with regards to microbial contamination indicates that bacteria and molds are common in Malaysia. Nevertheless, the knowledge of the health impact of such contamination is very low among the Malaysian communities.
The research in the indoor fungi, identification of specific pathogen and the consequential impact of the metabolites to the environmental health is still in infant stage. More research is needed while moisture intrusion and microbial outbreak is on the rising trend in Malaysia nowadays.
Statutory requirement relating to microbial growth and exposure limit is available for commercial and industrial buildings only. There is no guideline for residential buildings in Malaysia to-date. Nevertheless, we can adopt guidelines and recommendations from other international bodies with established guidelines and standards. The challenge lies on adopting these guidelines with the consideration in local environment.
Amidst of the gimmicks promoted by various vendors in improving indoor air quality, we must take more scientific measures in this aspect and adopt a systematic approach to prevent indoor microbial contamination by ensuring dryness, cleanliness and hygiene for our buildings and the occupants. Indeed, moisture control is the only measure and it is predominantly an engineering concern. In the event of microbial contamination, decontamination is the only effective mean to remove and control the contamination.
In conclusion, the construction design, construction quality control and routine maintenance is the bottom line for moisture control and prevention of microbial contamination.
1. C. Tischer*, C-M. Chen and J. Heinrich. Association between Domestic Mould and Mould Components, and Asthma and Allergy in Children: A Systematic Review. European Respiratory Journal. May 3, 2011
2. Prezone B., Weekers D., Miller D., Recognition, Evaluation and Control of Indoor Mold. America Industrial Hygienists Association, 2008. Pg 33 and 34.
3. Relative Humidity is defined as the ratio of the amount of moisture contained in the air to the maximum amount of moisture the air can hold at a given temperature
4. , , , , ., Prevalence of Penicillium specific Ig E level and allergy symptoms among office workers in a selected company in Bangi, Malaysia. National Institute of Health. 2007 Jun;24(1):37-46.
5. Cai G.H., Hashim J. H., Hashim Z., Ali F., Bloom E., Larsson L., Lampa E., Norba D., Fungal DNA, allergens, mycotoxins and associations with asthmatic symptoms among pupils in schools from Johor Bahru, Malaysia. Pediatric Allergy and Immunology. 21 November 2010. 290-297.
6. Characterization of Bacteria and Fungi Bioaerosol in the Indoor Air of selected Primary Schools in Malaysia. Sage Journal. May 4, 2011.
7. Indoor Air Quality: An Introduction to Health Professionals, http://www.epa.gov/iaq/pubs/hpguide.html
9. Stacey Foong Y. Y, F-N. Goh and Y. F. Ngeow, Legionella species and serogroups in Malaysian water cooling towers: identiﬁcation by latex agglutination and PCR-DNA sequencing of isolates, 2010. Journal of Water and Health. 98 – 99.
10. 2008 ASHRAE Handbook – HVAC System and Equipment. Section 16.1 and 16.2.
12. Sawyer, et. al 1913; Salls, 1927; Boeniger, 1995; American Lung Association, 1997; Al-Ahmady, 1997
15. Guide to Air Cleaners at Homes, United States of America Environmental Protection Agency, 2008. Pg 5.
16. Ditto. Pg 6 to 7.
17. , , , , , .. Inhalation challenge effects of perfume scent strips in patients with asthma. 1995 Nov;75(5):429-33
18. Burr, Chandler (2008). The Perfect Scent: A Year Inside the Perfume Industry in Paris & New York. Henry Holt and Co.. ISBN 978-0-8050-8037-7.
19. US Environmental Protection Agency. Should you have the air ducts in homes cleaned. 1997. Pg 1.
20. Prezone B., Weekers D., Miller D., Ditto.
21. IICRC S520 Standard and Reference Guide for Professional Mold Remediation. Institute of Inspection, Cleaning and Restoration Certification. 2008. Pg 103 to 132.