Indoor Air Quality and Green Building: Nexus for Sustainable Development
Introduction
According to studies by the United States Environmental Protection Agency (USEPA), an average adult spends 93% of their time on indoor activities. An adult can take 20-22 thousand breaths per day, i.e. more than 10 m3 of air, which is generally polluted and can pose a high threat to health. These health effects can be acute and chronic depending on exposure to pollutants. Immediate effects can be seen when concentrations are higher, whereas a long and continuous exposure to concentrations can be harmful in the long run. The quality of indoor air is affected by the presence of gases like carbon monoxide, ozone, radon, volatile organic carbons (VOCs) and fibers, along with particulate matter, organic and inorganic matter, biological components, etc. Sometimes these pollutants infiltrate from ambient air to the indoor environment resulting in a change in their concentration. Apart from the workplace indoor air environment, household air pollution is also kept under consideration where the effects are different, observed through biomass emissions, cooking gas emissions and dampness following household activities (Chen et al., 2015). When considering a green building, the environment it creates, the emissions or sink that it becomes has a lot to do with its inner environment. The ventilation rate is another factor to keep the indoor air monitored in a green building.
Indoor Air
The ambient air makes almost 40% of the indoor air which is a significant number to worry about (Zuo and Zhao, 2014). In recent studies, more importance has been given to the indoor air quality environment as it directly affects the safety, wellbeing and comfort of the occupants. Various studies of the quality and quantity of indoor air quality (IAQ) have shown a declining state. The relevance of the studies is directly related to the attention that indoor health issues get from the world media. The indoor air is affected by several physical, biological and chemical factors generated in the indoor or even outdoor environment making it a very complex subject (Chun et al., 2011). With increasing working time and development of good workplaces, people in general are more concerned about their indoor environment (Mayer, 2019).
In a day, 80-90% of the time humans spend in an indoor/closed environment. The composition and quality of the IAQ varies based upon the activities taking place in the building, the composition of walls of the building, various sorts of furniture, the ventilation and air-cooling systems (Young et al., 2019). The gradual changes in the composition and concentration within the buildings also need to be considered (Ancas et al., 2019). Hence, passive designing of buildings becomes very important as it will help in reducing the use of unwanted chemicals, reduced heat and gas generation. Natural ventilation, use of daylight and reduced electricity usage are also some important considerations in the indoor air environment.
Factors Affecting Presence of Indoor Air Pollutants
The major factors affecting IAQ are the presence of chemicals, dust, bioaerosols, temperature, humidity, ventilation and carbon dioxide (C02). Other affecting factors are relative to the type of local activities that are specific in nature. The chemicals floating around in air, and in the vicinity of the breathable zone (excluding the ceiling level and the bottom-settling gases) are generally VOCs. When these VOCs are in a higher concentration outdoors and keep flowing indoors, they pose a health hazard, and are usually generated from the use of cleaning products, fragrances, solid fuel burning, use of solvents and thinners in wall paints and some mixtures of building components. Smarter and greener choices of products for daily use can help in reducing such emissions. Also, the human respiratory system is the source of some VOCs and a sink for others.
In an open environment the dilution is higher while indoors the concentrations are higher and more effective. So, one of the key parameters is directly associated to space. The allergens in dust are dust mites: these are very minute creatures that feed on dead human skin and prolife in warmer environments. A single dust particle can contain multiple contents like fungal spores and dead skin cells. These, when settled in the respiratory tract, result in various other diseases, irritations, chest tightness, heavy/shorter breathing, sneezing and coughing problems. For these reasons, air purifiers are needed to remove the particulates. Humans and their activities, like respiration or perspiration, are also a major source of suspended fine particulate matter, oxidants and various other gases. (Young et al., 2019). Use of products, cooking fuels, carbonated beverages, fuels for vehicles, etc. in higher quantities act as an asphyxiant. Thus, in confined spaces, higher concentrations of C02 are harmful and to avoid such exposures, it is important to ensure a well-ventilated environment (Cong et al., 2018).
Humidity is an unavoidable part of the weather and it generally becomes higher when higher temperatures prevail. Some places have high humidity only in summer while some face it all year (Manuja et al., 2019). The humidity indoors results from higher temperatures than the outdoors, low or no ventilation, hot air in contact with cold surfaces, water leaks or damp walls. Also, at higher humidity levels development of molds and other bioaerosols occur, and inhalation of these is harmful.
Temperature has a significant role considering all the other factors, as at higher temperatures chemicals are dissolved at a high rate and they travel faster at higher temperatures. Allergens or bioaerosols have a tendency to increase at higher temperatures, whereas lower temperatures can cause shivering and numbness of limbs along with its effect on moods and work. Uncomfortable temperatures decrease w'ork efficiency, colder temperatures make us more relaxed and sluggish.
