How to Transform a Polluted Indoor Environment into a Healthy Home

With most of the world living in cities and growing villages, people tend to spend the majority of their time indoors. When not at home, we are working, learning, or even engaging in fun activities in enclosed, built settings. All in all, 90% of our time is occupied inside. It is therefore essential to ensure a comfortable, productive, and healthy indoor environmental quality by following well-regulated parameters and design practices that consider temperature, lighting, noise pollution, proper ventilation, and the quality of the air we breathe. The latter is especially important, since contrary to what we might think, air pollution is much higher indoors than outdoor.

Indoor air not only can cause discomfort and affect productivity but it could very well become a potential threat for occupant's health as it could hold a wide range of airborne and gaseous pollutants including volatile chemicals, particles, and biological contaminants. These elements tend to manifest in our immediate surroundings, embedded in many construction, finishing, or even daily use household materials. Increased levels of exposure can cause health issues such as asthma, infections, and intoxication. In fact, almost half of all respiratory illnesses are caused or aggravated by poor indoor air quality. 

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Outdoor air pollution - Indoor air quality / Illustrations by Elisa Géhin. Image Courtesy of Saint-Gobain

Furthermore, some of these contaminants cannot be easily detectable and sensed by home dwellers making them exposed to health risks. It is therefore important to learn about the various pollutants that are emitted or generated by most of the materials and products that shape the spaces we inhabit daily. We will explore the consequences of choosing some of the most common materials and will present some "active" products as alternatives that could even help improve indoor air quality. 

It is surprising to know that in many cases air pollution is 100 times higher indoors than outdoors. This would cause us to consider the numerous types and sources of pollutants that exist in our constant daily surroundings.

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© Francisco Nocito

What Are These Air Pollutants and How Do They Manifest at Home?

Indoor contaminants are of various sizes and compositions. They might be Microorganisms such as fungi and include Molds, which develop on surfaces and can be visually identified as foaming stained structures. They tend to grow in wet, warm environments (70% to 95% humidity level) and can be found in poorly ventilated spaces or wet material. Molds can release spores particles into the air, contributing to its spread and potentially harming occupants' health.

Other types of microorganism pollutants are bacteria, which are single-cell living organisms that are found all around us, whether on surfaces, air, in the dust, or in the water. While most bacteria are generally safe, some species can be harmful especially to vulnerable inhabitants. There are multiple sources of indoor bacteria as they can emanate from outdoor air, from the occupants themselves (ex. Daily material brought into the home) or from poorly maintained ventilation systems.

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© Guy-Joël Ollivier

Some biological pollutants could also be Molecular as Endotoxins (5), which are molecular complexes carried by certain bacteria. Allergens are also molecular type contaminants that can come from mold spores, insects, pets, rodents, and so on.

Particles including viruses and pollen constitute the third form of indoor air contaminants. They are also usually brought into the home from exterior sources (hosts or air airflow).

There are multiple common sources to airborne particulates which could emanate from outdoor air, cleaning supplies, and smoke. They could also develop due to inefficient designs causing inadequate air circulation and ventilation.

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Indoor air pollution / Illustrations by Elisa Géhin. Image Courtesy of Saint-Gobain

Other indoor air contaminants should also be mentioned. Carbon Dioxide (CO2) is a concerning indoor air pollutant that can have harmful effects on human well-being, yet its main indoor source of emission is simply created by exhaling inhabitants, tobacco smoke or through household appliances combustion. Noting that, the typical CO2 Outdoor Air Values ​​(OAV) are between 300 and 500 ppm, they tend to be much higher indoors with a recommended maximum concentration between 600 and 1000 ppm depending on the adopted standards.

As for Volatile Organic Compounds (VOCs) of which Formaldehyde (5) are most common, they can emanate from construction and finishing material, manufactured or natural alike, of which binders, glues, coatings, paints, and even wood to name a few. They could also originate from home furniture (fabric and carpets) or everyday chemical cleaning supplies. VOCs are extremely concerning as they can easily evaporate at room temperatures and are found in much higher concentrations indoors due to the lack of oxidizing UV light indoors.

Lastly, some common gaseous contaminants such as Radon gas are simply found in the earth by the decay of naturally occurring uranium in soil and water and would spread out into homes through the air and building foundations.

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© Sweng Lee

However, different microorganisms behave differently in standard environments. For instance, when certain enabling conditions (temperature, water availability, nutrients, etc.) are in place, bacteria or fungi (including molds) multiply and proliferate. This applies in water, air, and on inanimate surfaces. Yet, viruses only survive for certain finite periods in such environments. They are inert outside their host and cannot multiply. Hence the need to include a solution that would treat all forms of pollutants in different conditions.

Effects of Indoor Air Contaminants on Human Health

Depending on various factors and rates of exposure, indoor biological pollutants would affect the household dweller's well-being. In a less than optimal indoor condition VOCs, CO2, molds, and other pollutants would accumulate, thus creating serious health issues. A sensitive occupant continuously exposed to certain biological pollutants could develop asthma especially whiting settings with signs of humidity or presence of mold. In fact, early exposure to molds has been associated with asthma affecting young children.

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© Hiroyuki Oki

Some types of Indoor Air pollutants have also been linked to Headaches and concentration problems, as multiple studies (4) suggested that increased levels of CO2 affect people's performance. The results showed that cognitive function would be less efficient with higher rates of CO2. This proved that indoor air pollution impacts the user's performance and productivity.

Other chemicals and contaminants (VOCs of which Formaldehyde) have also been suspected/proven to affect the occupant's concentration. In addition to that, they might cause more serious issues such as irritation, allergic reactions, infection, and intoxication. The American College of Allergy, Asthma & Immunology had also stated that 50 percent of all respiratory illnesses are caused or aggravated by poor Indoor Air Quality.

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© Takumi Ota

Recommended rates can be found through various standards of which ASHRAE 62.1 or even some WHO guides. These references are a valuable resource while designing any project since they specify the ventilation rates needed for new constructions and the ones needed to improve the indoor air quality of existing buildings. Many of those standards also highlight the maximum airborne contaminant levels (specific to each pollutant) required to maintain acceptable indoor air quality.

Nevertheless, measuring biological contaminants is still not an easy and accessible option for regular building users. Inappropriate rates of indoor air pollutants are therefore rarely denoted before physical discomfort and potential health complications arise. Since it is hard to control or fix what cannot be measured designers should turn to preemptive efficient design solutions to reduce and control indoor air pollution.

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© Mariela Apollonio

What Are The Challenges?

Aside from the inability of occupants to easily and constantly measure the rates of indoor air pollutants, other difficulties are to be highlighted. For one VOCs and other gaseous contaminants cannot be filtered or captured.

Another point to bear in mind would be that biological contaminants cannot exist in our environment unless they have liquid water. Humidity allows the growth and propagation of indoor air pollutants. Then again moderate levels of humidity between 30% and 60% are also a means to achieve indoor Human comfort. In other words, we thrive in much of the same range as some of the biological contaminants around us.

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© Creative Photo Room, Maria Efthymiou

What Are the Best Remediation Strategies?

Good architecture and design are the most important means of reducing and controlling the growth of indoor air pollutants. Architects should consider multiple parameters even before setting to design a home or building to grantee occupants comfort and well-being. Proper ventilation, exposure to natural light, building envelope insulation, and sustainably sourced non-toxic material are among the practices to consider while working on any project. A comfort based mindset should ideally be adopted from the pre-design phase all the way to the post handing over maintenance. There are many smart design solutions to provide a healthy indoor air quality.

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© Pedro Kok

Proper natural ventilation is one of the first considerations while designing a home. Building orientation and a well-studied openings layout would promote an effective airflow through the space (cross ventilation, cooling towers). Implementing a functional hybrid ventilation system indoors would contribute to the dilution of some contaminants.

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© Dilanka Bandara

Along with designing a proper and well-controlled aerated dwelling, the architect should consider managing building air leakage by maintaining a stable indoor air pressure. Even though natural ventilation is important, it also entails that whatever air is lost must be replaced to have a neutral indoor/outdoor air pressure. It is crucial not to allow unchecked air infiltration as this would potentially bring in additional pollutants.

Despite the fact that natural ventilation is generally preferred as it is considered to be CO2 free and that most standard mechanical systems use lots of energy, risks could arise through unstudied natural air renewal in the home as outdoor emissions such as traffic pollution and other micro-particles might be brought inside. Isolating connecting spaces is a manner of minimizing the stack effect. Disconnecting building spaces and compartmentalization is another consideration while designing the project.

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© Fernando Alda

In addition to the above, the most effective means would also be to implement smart mechanical ventilation/air-conditioning systems with proper filtration and heat/cold recovery. Complementary to natural ventilation, artificial indoor heating and cooling systems could be equipped with specific filters that would reduce the rates of airborne particulates. Bearing in mind that standard fiberglass panel filters are not always most effective as the recommended Minimum Efficiency Reporting Value or MERV should be at 8 and higher (according to certain standards) whereas typical home filters are at 4 or 5. Proper filters are generally not adaptable to all standard ventilation systems and would require constant upkeep.

Effective ventilation and filtering standards can also be reviewed through the Science for Policy report by the Joint Research Center (JRC). It is an informative European standards base to revert to as it introduces the HELTHVENT WP5 Report (2012) which assesses ventilation standards related to Indoor Air Quality and compares them between 16 countries. It is an especially important document to follow up on mechanical ventilation filtering recommendations which are still not too commonly applied in European dwellings.

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© Emma Cross

Another highly important step would be to control the humidity and promote de-humidification. This begins by having a dry construction process including steel or timber framing. A dry foundation and building envelope are key to maintaining a controlled humidity rate that would be comfortable to occupants yet inhibiting the growth of molds or other pollutants. Seeking dry construction and finishing material is also a good step to promoting a healthy indoor air quality.

Finally, one of the most effective ways to mitigate the propagation of indoor air contaminants is by choosing the best material. It is possible to reduce and remove pollution sources. This can be done by using non-toxic modern materials that are purposely created for safe indoor constructions and use. Seeking Green labeled or Health certified items is a good solution to diminish indoor air polluting. Designing buildings and homes with new technology manufactured items can also contribute to much-coveted certifications like BREEAM, LEED, and WELL (rating systems).

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© James Morris

Materials such as the Activ'Air® ceiling and plasterboard are even contaminant capturing and dilute up to 70% of VOCs found indoors. They offer a passive and therefore long-lasting technology that would not deploy the captured gases regardless of the temperatures. They require no maintenance and regulation and would, therefore, be more effective in reducing formaldehyde than additional ventilation.

Their practicality also lies in the fact that they are set into the base of the building or interior, as opposed to superficial finishing material (ex. Coatings) which would be more prone to damage and do not offer the same purifying functions. Note that the Activ'Air® panels are just as effective through layers of water-based, acrylic, or epoxy paints and breathable wallpaper (tested in Eurofins and VITO lab to assure the audience of third party validation inc. Conforming to EN 16000-23). Going for such smart materials would also allow flexibility in creating aesthetically pleasing and clean homes. Noting that functional and healthy spaces should not necessarily look boring or sterile.

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Activ'Air diagram. Image Courtesy of Saint-Gobain

Implementing these toxin diluting material is one of the easiest ways to maintain a safe indoor air quality as it offers a more practical and affordable solution for new constructions just but also for pre-built restoration and renovation projects. The latter are often constrained within impractical settings with a lack of proper ventilation and light infiltration. Most importantly older apartments and houses might often have an increased level of humidity. VOC eating drywall is therefore the ideal way to counteract existing molds and biological contaminants in a pre-constructed home, since Activ'Air® works even after multiple renovations and re-decorations, permanently reducing formaldehyde. It provides long term formaldehyde absorption, based on tests and analysis.

As the last couple of months have shown Humans can face new unseen health risks. Spending time indoors has therefore been considered as a solution. Nevertheless if unmaintained, unchecked, and improperly designed, our homes can harbor many air pollutants, causing mild and serious discomforts alike. A few smart choices would therefore go a long way, consciously managing the environmental quality of the spaces and increasing our general well-being.

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© Monika Sathe Photography


  1. How to Minimize Harmful Effects of Formaldehyde Gas Indoors
  2. Cross Ventilation, the Chimney Effect and Other Concepts of Natural Ventilation
  3. Understanding and Improving Indoor Air Quality (IAQ) & (VOC eating drywall)
  4. Indoor Air Quality impacts user's performance and productivity
  5. Biological Pollutants of Indoor Air
  6. British Gypsum Saint-Gobain, ACTIVair Infographic How Important is Air Quality?
  7. British Gypsum Saint-Gobain, Desk-based research into volatile organic compounds (VOCs) and indoor air quality
  8. Promoting healthy and highly energy performing buildings in the European Union
  9. IAQ Standards and Guidelines (EPA and ASHRAE Standard)
  10. Air Pollution: Wood Smoke and Lung Health

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About this author
Cite: Hana Abdel. "How to Transform a Polluted Indoor Environment into a Healthy Home" 29 Jun 2020. ArchDaily. Accessed . <> ISSN 0719-8884

© Hiroyuki Oki


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