Buildings are constructed to provide habitation for people. Whether for dwelling or occupation, inhabited structures have to control the indoor environment within which people carry out their endeavors.
Mitigating the effects of indoor pollution does not have to be sophisticated and expensive. What is essential is the awareness of the various pollutants and their effects that are present in built environments. These pollutants, or contaminants, are classified into three types and each of them occupy an equal volume of space inside buildings.
Gaseous pollutants, also known as volatile organic compounds (VOCs), are chemicals that contain carbon that easily become vapors or gases. Most of these VOCs are man-made and the major sources are common building finishes such as protective coatings, paints, adhesives, and solvents. Formaldehyde is a respiratory irritant that is emitted from wood materials. High relative humidity and temperatures cause the rapid vaporization of this VOC.
Environmental tobacco smoke (ETS), or second hand smoke contains about 7,000 chemicals, with 250 identified as harmful, and at least 69 of the toxic chemicals cause cancer. Hydrogen cyanide, carbon monoxide, and ammonia are some of the harmful chemicals in ETS. Benzene and vinyl chloride are two of the carcinogenic chemicals in ETS. Incidentally, benzene and vinyl chloride are ingredients in the manufacture of plastics and resins.
Carbon monoxide (CO) is a poisonous, odorless, tasteless gas. It is the product of incomplete combustion. CO is harmful when breathed because it displaces oxygen in the blood and can cause cardio-pulmonary problems. Common sources of CO are from fuel-driven vehicles and open-flame cooking stoves using gases, gasoline, coal or wood.
Carbon dioxide (CO2) is a natural product of human respiration. It enters the body through the lungs and is distributed to the blood, resulting in acid-base imbalance, or acidosis. Moreover, in a research done in the Berkeley National Laboratory, it was determined that moderate concentrations of CO2 can impair a person’s decision making.
While almost gaseous pollutants are more from man-made products, biological contaminants are, or are produced by, living things.
People with communicable illnesses such as influenza, measles, chicken pox, and tuberculosis can transmit these infirmities through the air. From indoor plants and furred pet animals come pollen and allergens. Urine from rodents are very potent allergens, that, when dried, can become airborne and inhalable. Insect-derived particles can trigger asthma.
Fungi or molds, mildew, and yeasts are biological pollutants that can release disease-causing substances linked to infections, bronchitis, and hypersensitivity disorders like nasal stuffiness, coughing, irritations to the throat, eyes, skin. Some types of fungi can alter white-blood cell count. These types of contaminants breed in warm and humid conditions. Water-soaked materials, like damp carpets and other hygroscopic materials, and surfaces where condensation is present allow accumulation of biological contaminants. Indoor relative humidity at 65% and higher provide the conditions for fungi and mildew to grow.
Other places where biological impurities can thrive are in stagnant water, in the basins of poorly maintained cooling towers, and cooling coils and condensate drain pans of air-conditioning equipment.
Particulate contaminants are commonly known as particulate matter. Particulate matter is a complete mixture of solid and liquid particles suspended in the air. Particles that are larger than 30 microns in diameter are unlikely to enter nasal passages. Inhalable particles are smaller than 10 microns, or PM10. Fine or respirable particulates, PM2.5, with 2.5 microns in diameter which are termed as aerosols or mists, lodge themselves deeply in the lungs and accumulate, potentially leading to respiratory issues.
Outdoor PM2.5, which is more of soot from motor vehicle exhaust, can be brought into indoors from outdoors by mechanical systems that supply ventilation air into the building to dilute VOCs, or, if the buildings have negative pressure, PM can infiltrate through door and window cracks, and other building openings.
Indoors, particulate matter is generated from human activity. A seated person can generate 400,000 particulates per minute. Since particulate matter are hygroscopic, they will absorb the VOCs, oxidants, and viruses that can be inhaled. There are also biological particulates, as described earlier, that are classified as particulate contaminants.
MITIGATING EFFECTS OF CONTAMINANTS
It is because of these contaminants and their consequences on the well-being of building occupants that indoor air quality is being promoted vigorously as an essential aspect of green buildings. The principles on how to mitigate the effects of these contaminants might appear simple: dilution of gaseous contaminants with adequate ventilation of air, control of temperature and humidity to prevent biological growth, proper air filtration, and prevention of contaminant migration. But these can pose serious challenges to improving efficiencies in building systems. It can also further add twists to the oft-contentious issue on increased building cost.
It is to everyone’s benefit that the Philippine Green Building Code includes, as mandatory provisions, the ventilation rates for dilution of contaminants, and designation of smoking areas inside and outside of buildings.
“The value of health and productivity of the occupants in a building may be more than an order of magnitude greater than the cost of energy that it consumes.” — William Bahnfleth, ASHRAE President 2013-2014
Emmanuel C. Punsalan is a partner at L. R. Punsalan and Associates and is past president of ASHRAE Philippines Chapter.