Indoor Air Cartoon Journal, June 2021, Volume 4, #119
The success of risk management is largely based on what can be controlled. Control is about having the power to prevent, correct, change or dictate the course of an event. Prevention is a control done through avoidance. Correction is a control done to change the cause of an unwanted or unaccepted event that occurred to a wanted or accepted one. Change is also action taken when an event has already occurred. However, a change could be from a positive to a negative direction or vice versa. Since risk is a negative term, the goal of the control is to move from a negative to a positive direction and preferably prevent the occurrence of a negative event.
Efforts should be made to control a hazard and vulnerability to reduce the risk of poor human health and comfort, poor perception of the environment, and poor performance occurrence caused by air pollutants in the indoor environment. Air pollutants are hazards. The vulnerability of interest in this article is vulnerability due to exposure. Discussions on other vulnerabilities can be found in this journal.
Occupants of an unhealthy indoor environment are vulnerable to being a victim of harm caused by air pollutants. Thus, controlling the sources of air pollutants that compromise the healthiness status of the indoor environment is a way of controlling occupants’ exposures. These air pollutants could be chemical, biological, and particulate matters in nature. The intake of chemical, biological, and particulate matter pollutants into the human body could occur via inhalation, skin uptake, or ingestion.
Exposures to pollutants could occur when they are in indoor air or on indoor surfaces. For the simplicity of this article, exposures to pollutants when they are in indoor air is the focus of this article. The amount of indoor air pollutants an occupant is exposed to is equal to the multiplication of the concentration of air pollutants and duration of exposure.
The concentration of an air pollutant in indoor air is the ratio of the amount of the air pollutant emitted to a volume of air in the indoor environment to the amount of the air pollutant removed from the indoor air. In simple terms, concentration is the ratio of source to sink (removal). The goal is to ensure the sink removal rate is higher than the source emission rate to achieve a low concentration. Understanding the sources of pollutants found in the indoor environment is useful to reducing source emission rate, adopt appropriate sink, and increase sink rate.
Sources of indoor air pollutants can be from outdoor and indoor environments. The focus of the discussion will be on indoor sources. Sources of indoor air pollutants can be broadly categorised as (i) human and pet metabolism and chemical release, (ii) work and living processes, (iii) point source matters, and (iv) contagious virus host. Water vapour, carbon dioxide, odours, and particles resulting from human body metabolic activities are examples of emissions from human metabolism.
Human surface chemistry between human skin lipids and oxidising agents like ozone could be a source of chemical-based pollutants released into indoor air. Work and living processes are activities or series of actions leading to the emission of air pollutants. Examples of work and living processes include food preparation, work-related activities, laundry, personal hygiene, etc.
If emissions from the four source categories are left unattended and active, indoor air pollutants concentrations will keep increasing. Thus, a control strategy is needed to reduce the emissions and indoor air pollutants concentrations. The control strategy, which is ventilation, for the human metabolism and chemical release and work and living processes source categories is targeted towards the emitted air pollutants.
The concentrations of emitted air pollutants from human metabolism and chemical release are reduced through the dilution phenomenon provided by the control strategy. The concentrations of emitted air pollutants from work and living processes can be reduced through local exhaust and the dilution phenomena provided by ventilation control strategy.
Additionally, good design practices could aid the reduction of air pollutants emissions and indoor air pollutants concentrations. A poor design leading to a high occupancy density in an indoor environment will increase the concentrations of air pollutants emitted from human metabolism and chemical release. A poor design leading to poor locations of work and living process activities and poor application of the control strategy could increase occupants’ exposures to indoor air pollutants that could have been avoided.
Unlike the first two categories, the control strategy for point source matters is source control and targeted primarily towards the sources through removal, restriction, and prevention phenomenon. That means point source matters are controllable sources. Thus, ventilation should not be used as the primary or only strategy for the point source matters.
If controllable sources of air pollutants are not controlled, the costs of using ventilation and other engineering solutions, such as air filtration and air cleaning, as cover-ups to reduce indoor air pollutants concentrations will keep increasing. The unnecessary investments in costs to reduce the concentrations of indoor air pollutants from sources that should not be in the indoor environment in the first place are waste.
This kind of waste is called inventory waste. Inventory waste occurs when resources are consumed to cover up symptoms of a problem inherent in a process without eliminating or reducing the cause of the problem to eliminate or reduce the problem in the process. Thus, the root cause of the indoor air quality (IAQ) problem should be identified, then removed, or restricted. The potential root cause of the problem or factors contributing to the IAQ problem should be determined and avoided to prevent inventory waste from occurring.
It is not uncommon to find some architects, engineers, and interior designers not prioritising their specifications to control point source matters in their buildings or facilities. To deliver healthy and energy-efficient indoor air, they might be forced to over-provide for mechanical ventilation. Building owners, facility managers, and tenants might also be forced to rely on ventilation unnecessarily to reduce the risk of poor human health and comfort, poor perception of the environment, and poor performance occurrence.
Ventilation is essential and should be adequately provided, but it should not be used as a cover-up for the effects of poor design and specifications. The provision of adequate ventilation and other engineering solutions is essential, especially since there is a need to control air pollutants emitted from human metabolism and chemical release and work and living processes.
Ventilation and other engineering solutions will still be useful to reduce concentrations of air pollutants from point source matters that are unknown, cannot be predicted, or only restricted because they cannot be removed or avoided. Continuous improvement efforts should also be made to see how the point source matters generating air pollutants can further be restricted and preferably removed. Aside from designers, facility managers, tenants, and owners also have a role to play to prevent, restrict or eliminate the point source matters.
The unnecessary consumption of resources to reduce indoor air pollutants concentrations, i.e., usefulness to be delivered to consumers or customers, will reduce the value delivery. The reduction of value delivery is tantamount to healthy and energy indoor air delivery efforts moving toward the waste end of the waste-value delivery spectrum. An increase in the delivered usefulness for every unit of cost invested will move healthy and energy indoor air delivery efforts toward the value end of the waste-value delivery spectrum.
Due diligent consideration for prudent use of invested costs to maximise the delivery of healthy and energy-efficient indoor air is important, especially in a world experiencing the adverse effects of climate change, as discussed in article 118 of this journal. Digital solutions adoption grounded in lean thinking can be used to reduce waste occurrence, specifically the type of waste called inventory waste. Designers can use digital solutions to have easy access to information on air pollutants emission rates and the kind of air pollutants that could be emitted from potential sources in buildings or facilities.
There is also a potential for using digital solutions to simulate how emitted air pollutants could compromise media, e.g., air, that carry the pollutants to different microenvironments in the building or facility and estimate exposure per person per time. Facility managers can also use digital solutions as described to inform their operations and renovation activities. Facility managers, tenants, and owners will also benefit from sensors in several parts of their buildings to get real-time information on indoor air pollutants concentrations for several microenvironments in a building or facility.
In essence, digital solutions can reduce the time and other resources consumed for accurate problem definition before and after a problem occurs, root-cause analysis, and insights into how possible solutions can be adopted in a value-oriented manner. Aside from digital solutions adoption, efforts should still be made to control the known controllable sources.
The fourth category, contagious virus host, is also a controllable source. The control strategy for this category is targeted primarily towards the sources through prevention phenomenon. Removal and restriction are not as effective as preventing someone with a contagious virus, like Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2), the virus causing COVID-19, from entering a building or facility.
The development of digital solutions that can detect someone with COVID-19 within seconds will improve the effectiveness of preventing an infected person from occupying a building or facility. The development of such a digital solution is a possibility. The rapidly developing research and development efforts in Singapore are a testament to the possibility of developing digital solutions that provide the prevention benefit. Below are examples of the research and development efforts.
At the moment of writing this article, research and development scientists from Silver Factory, a spin-off from Nanyang Technological University, Singapore, developed a breathalysers test system called TracieX breathalysers that can detect someone with COVID-19 with 95% sensitivity and 97.8% specificity within 2 minutes.
Another group from Breathonix, a spin-off company from the National University of Singapore, developed a breathalysers test system that uses VOCs biomarkers to identify someone with the COVID-19 in less than 60 seconds. The breathalysers test system is called The BreFence Go COVID-19 breath test system. It has 85.3% sensitivity and 97% specificity.
Efforts, supported by the Singapore Government, are still being made to improve the effectiveness of the breath test systems. Building owners, facility managers, or tenants can use a breath test system or other digital solutions that serve the same purpose to control the controllable source, contagious virus host, in an energy-efficient manner.