Cooking shows have never been more popular around the world than they are now. Whether from recipes, reality shows, or documentaries, writer Michael Pollan points out that it is not uncommon to spend more time watching than preparing our own food. This is a very curious phenomenon, as we can only imagine the tastes and smells on the other side of the screen, which the presenters often like to remind us. At the same time, when we watch something about the Middle Ages, polluted rivers, or nuclear disasters, we are relieved that there is no technology to transmit smells across the screen. In fact, when dealing with odors (more specifically the bad ones), we know how unpleasant it is to be in a space that doesn't smell good. When dealing with buildings, what are the main sources of bad smells and how can this affect our health and well-being?
Dealing with odors can be tricky. First of all, it is essential to mention that what one person considers stinky and disgusting may not be for someone else. These preferences are subjective and may vary widely due to differences in culture and personal experience. Of course, there are some odors that are unpleasant for everyone. When excessively strong, they can disturb physical and psychological comfort and even cause nausea, headaches, and irritation in the eyes, nose, and throat. If they sustain over a long period of time, they can also affect mood, anxiety, and stress level. In Denmark, for example, a study  found that volunteers experienced reduced productivity in an office when a 20-year-old rug was placed in the environment, emitting odors and air pollutants.
An adult inhales and exhales about 11,000 liters of air daily. Odor is caused by one or more volatile chemical compounds that humans and animals can perceive through smell. According to the report Guidelines for Ventilation Requirements in Buildings , humans perceive air in two ways. The first, sense of smell, is located in the nasal cavity and is sensitive to several hundred thousand odorants in the air. The second, general chemical sense, is located on all mucous membranes in the nose and eyes and is sensitive to an equally large number of irritants in the air. It is the combination of these two senses that determines whether the air is perceived as fresh and pleasant or rancid and irritating.
From this study, two odor measurement units were developed: olf and decipol. Olf is a pollution emission rate, while decipol is the level of smell perceived by the user. But more important than identifying the intensity is finding the source of the odor. For that, there are portable olfactometers, used by specialized professionals, that allow users to quantify and quickly identify the source of annoying odors.
In buildings, odors can come from external or internal sources. External sources are, of course, more complicated to control. They can reach the building through openings and air renewal systems and may stem from industrial activities, highways, an unpleasant neighbor, busy streets, sanitation infrastructure, or even chemical soil pollution. The internal sources of odors in a building may include the building materials themselves, the coatings and paintings, the furniture, the sewage system, construction materials, conservation and maintenance materials, decomposition products, or users and their belongings.
It is important to differentiate odors from indoor air pollution. Unpleasant odors may not always be polluters—for example, cooking gas releases an odor in the event of a leak. Many harmful pollutants are also odorless. One category of pollutants, Volatile Organic Compounds (VOCs), deserves a specific mention. Among them, formaldehyde (with an intense odor) is the most common, and may emanate from manufactured or natural construction and finishing materials, including binders, glues, coatings, paints, and even wood, to name a few.
But how is it possible to improve indoor air quality? Although cleaning products can cover up bad smells, the best way to improve indoor air quality is to stop the pollution of the source. Some points of consideration deserve more attention. Non-siphoned sewers and drains are potential sources of malodor. Moreover, finding out if building materials give off unpleasant aromas or harmful substances is vital to maintaining good air quality. There are already some products on the market that promise to purify indoor air by eliminating certain volatile organic compounds (VOCs) like formaldehyde.
In addition, as architects, providing good sunlight and, above all, adequate and natural ventilation is a highly efficient way to purify air in an environment. Facilitating air circulation helps to improve thermal and olfactory comfort in an environment. If this is not possible, the use of mechanical ventilation with fans and air conditioners can work efficiently as well. In the case of air conditioning, inlet and outlet air filtration helps to remove harmful particles. However, air filters need to be maintained to prevent the ventilation system itself from becoming a source of pollution.
Another element that can improve indoor air quality, in addition to its many other benefits, is plants. They produce oxygen, eliminate toxins from the air, and add aesthetic value to a space. Some species have already proven to be more efficient than others. NASA  studied chrysanthemum (Chrysantheium morifolium) and concluded that they absorb polluting gases, such as carbon monoxide and formaldehyde, and eliminate harmful elements such as benzene. Rapid lily and palm also absorb some pollutants. This link provides a more comprehensive list of the types of plants studied. Other species, such as jasmine, geraniums, lavender, and basil, release pleasant fragrances capable of neutralizing unpleasant odors.
Although there is no evidence that unpleasant odors, in themselves, are directly linked to adverse health effects, scientific research amply proves their harm to the general well-being of occupants. Creating at least neutral-smelling environments may be more essential to architecture than we think. And by using materials sensibly, we might be able to smell those nice fragrances that we can't access through TV shows.
 Saint-Gobain. Indoor Air Quality impacts user's performance and productivity. Available in this link.
 European Concerted Action: Indoor Air Quality & its impact on man. Guidelines for Ventilation Requirements in Buildings. 1992. Available in this link.
 Wolverton, B. C.; Douglas, Willard L.; Bounds, Keith. A Study of Interior Landscape Plants for Indoor Air Pollution Abatement. 1989. Available in this link.