Thick Air (Part 3) – Indoor Air Quality, SARS-CoV-2 and Healing Processes in Hospitals

Preliminary remark of the author 
What does air have to do with design?

The author is neither an infectiologist nor a specialist in outdoor or indoor air issues. The idea of this three-part blog is rather to present current research results in an increasingly confusing situation around SARS-CoV-2 and to put them into a wider context. The common “silo thinking” contains the risk of losing track of one of the most burning issues of the day. The focus of the following considerations is on the importance of air as an elementary part of a recovery process. These considerations are in line with my earlier blogs, which highlight related issues of colour, noise and light (will follow). Air is the element that is least visible, but its design is fundamental. Air and its treatment in air currents are also subject to design, which is particularly important for the healing process. As a place of healing and convalescence, the air quality in hospitals is of an almost elementary importance. In addition to hygiene and safety, precise ventilation and air conditioning contributes to better indoor air quality, thus also to faster patient recovery and demonstrably higher staff productivity. 

We focus on the currently known and scientifically proven correlations between the SARS-CoV-2 transmission rate and bad air in 3 parts as follows: 

  • Part 1 reflects on the relationship between climate change and air quality 
  • Part 2 focuses on air as one of the 9 basics of “healthy buildings”
  • Part 3 examines the relationship between air quality and healing processes in hospitals. 

The statements are based on the research results that have been made available to date, most of which are still scarce, and require ongoing scientific reviews and modifications. They do not claim the status of conclusive findings, but are intended as food for thought-provoking impulse. 

Deutsches Ärzteblatt 51-52/2014

Air as a Aasic Component of Life 

Along with light, air is one of the most elementary basic components of life, ahead of food and water. Air contains 78% nitrogen and 21% oxygen, with the remaining percentage consisting mainly of the noble gas argon. Every person breathes in between 12 and 24 kg of air per day, depending on age and activity.  
Air is therefore synonymous with life, as it provides people with vital oxygen. If the immune system is disturbed or defective, the lack of breathing air can become life-threatening. With every breath the body can also absorb dirt particles, bacteria or viruses. A healthy body can easily cope with this, but a sick body cannot. 
Good indoor air quality plays an important role in the healing process and well-being in hospitals and other healthcare facilities. Life depends on it. 

However, numerous studies (1) have shown that the air quality in hospitals is not optimal. But they also show that clean indoor air can help patients to recover better and reduce physiological stress.

In 2007, American scientists were able to establish a correlation between rising flu cases and indoor air humidity for the first time.  
They found that at a relative humidity of between 20–35%, the risk of contracting an influenza A virus is about three times higher than the average room humidity of 50%. The reasons for this include the faster and wider distribution of the fine droplets and the longer life of the viruses in excessively dry air. (2, see also part 2 of this blogpost)

Physicists at the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig and the CSIR National Physical Laboratory in New Delhi have been studying the physical properties of aerosol particles for years to determine the effects on air quality. Among other things, they evaluated a total of 10 international studies that investigated the influence of air humidity on survival, spread and infection with the pathogens of influenza and the coronaviruses SARS-CoV-1, MERS and SARS-CoV-2 between 2007 and 2020. 

Result: Air humidity influences the spread of coronaviruses indoors in three ways:  

  1. the behaviour of micro-organisms within the virus droplets 
  2. the survival or inactivation of the virus on surfaces 
  3. the role of dry indoor air in the transmission of viruses via the air. (3)

Sick patients in a healthcare facility can contribute to a deterioration in air quality: coughing can pollute the air in a hospital room, open wounds or infections can transfer viruses and bacteria from the patient’s body to surfaces of other materials. In addition, activities and person density affect the indoor air quality of the intensive care unit environment, especially in terms of coarse particle concentration. (4)

Building Renovations Reduce Air Exchange Rate 

A large part of the air circulating through a hospital is supplied from outside. Indoor air quality is therefore very much dependent on outdoor air quality.  
Many public hospitals in urban areas were built decades ago. Piping and ventilation systems no longer meet the current technical standards everywhere. As a result, the air entering the hospital cannot be adequately filtered. This means that known pollutants such as dust mites, dirt, pollen and airborne bacteria can circulate much more easily through the ventilation system. (5)

Until the end of the 1970s, little attention was given to the air-hygienic effect of ventilation systems. In German-speaking countries, the greatest changes for the implementation of uniformly standardised surgical ventilation systems did not occur until after the year 2000. (6)
The aspect of fresh air supply also received too little attention in the numerous building measures of the last decades. Especially the thermal insulation measures to save energy resulted in a significant reduction of the air exchange rate and thus an increased accumulation of indoor air pollution. Overall, modern technologies and new materials, building materials, interiors and technical equipment of buildings (and thus also their emissions) even worsened indoor air.

Indoor Air Quality  

Indoor Air Quality (IAQ) comprises a variety of factors: typical measurements include temperature, humidity, quantity, presence of chemicals and other contaminants and the quality of the outdoor air brought in. The quality of outdoor air, which is important for the human organism, consists of a sufficiently high number of negative ions. The negative ion is an important source of energy in our body. It is one of the strongest air-purifying agents in nature. Negative ions play an important role in cell function in the organism, blood purification, strengthening of the immune system and autonomous nervous system. The amount of negative ions in the human organism inside the cell and outside the cell wall is essential for their function. When negative ions flow into the body, channels in cell walls open, toxins  are excreted, hydrogen is absorbed into nutrients and new healthy cells are formed. Negative ions can be found in dense concentrations, especially in natural environments, and are massively reduced in an urban context. (7)  

However, research into ion concentrations in the air is still in its infancy and is therefore an aspect that has received little attention in the assessment of air quality.  Unfortunately, due to the dense construction of today’s houses and buildings in indoor environments, this function can hardly develop. They are neutralised or bound by pollutants, CO2, electrosmog, fine dust, exhaust gases and many more. Negatively charged ions in sufficient quantities can only be produced in clean air. This is shown by the list of measured values at specific locations: 

Measured values of ions (per cm3 air): 

  • Near waterfalls: 20,000–70,000 ions  
  • In the mountains or near the sea: 4,000–10,000 ions  
  • On the outskirts of town, on meadows: 1,000–3,000 ions  
  • In the city: 200–500 ions  
  • In closed rooms: 20–100 ions 

This small overview makes it immediately clear, that the best air purifiers in a hospital cannot be AC-systems, but fresh air and sunlight (8) – both elements which are hardly accessible to patients in hospitals today. At the beginning of the 20th century, these components were still considered effective factors in respiratory diseases (e.g. tuberculosis). At the end of the 1920s there were no fewer than 88 sanatoriums in Switzerland – institutions like the ones described by Thomas Mann in his novel “Zauberberg”. However, the “climatic health resorts” were then successively substituted in advance with the use of drugs (including tuberculin by Robert Koch).

Coronavirus SARS-CoV-2 Spreads More Indoors at Low Humidity

Today, numerous research results show that more attention should be paid to indoor air to prevent future outbreaks of disease. The moisture content of indoor air is an important aspect but not the only one. Fresh outdoor air can also reduce the risk of transmission. Therefore, to contain the Covid-19 pandemic, it is very important to create and implement standards for indoor humidity in rooms with many people, such as hospitals, open-plan offices or public transport, writes a research team in the journal Aerosol and Air Quality Research. (9) 

A comprehensive improvement in air quality also makes a significant contribution to reducing costs in the health sector, as already demonstrated by a Rand Corporation study from California in 2005-2007. Air pollution is detrimental to human health, with adverse effects ranging from restrictions on physical activity, emergency room visits for asthma and hospitalisation for respiratory and cardiovascular diseases, to premature mortality. The economic costs of such effects are considerable. (10)


(1) See for example

Lagravinese R., Moscone F. et al. The impact of fair pollution on hospital admissions: Evidence from Italy. 2014.

Ballester F., Tenías J.M., Pérez-Hoyos S., Air pollution and emergency hospital admissions for cardiovascular. 

(2) Source: Lowen, A. et al.: PLoS Pathogens.2007.

(3) Ahlawat, A., Wiedensohler, A. and Mishra, S.K. (2020). An Overview on the Role of Relative Humidity in Airborne Transmission of SARS-CoV-2 in Indoor Environments. Aerosol Air Qual. Res. (in press). DOI: 10.4209/aaqr.2020.06.0302

(4) Chin-Sheng Tang, PhD, Feng-Fang Chung, MSc, Meng-Chih Lin, MD, and Gwo-Hwa Wan, PhD, Taipei, Tao-Yuan, and Kaohsiung, Taiwan, Impact of patient visiting activities on indoor climate in a medical intensive in a care unit: A 1-year longitudinal study.

(5) Moisture in particular poses a particular problem in pipelines. This often leads to problems such as mould and spores, not to mention the possibility of salmonella and nosocomial infections, which can become a significant health risk far beyond compromised air quality. 


(7) Eckert Jan, Ionised indoor air; Review on the application of ionised air in indoor environments. HSLU, Technology & Architecture 2013, ISBN 303303859X, 9783033038592 

Shu-Ye Jiang, Ali Ma, Srinivasan Ramachandran*, Negative Air Ions and Their Effects on Human Health and Air Quality Improvement, Int J Mol Sci. 2018 Oct; 19(10): 2966.  Published online 2018 Sep 28. doi: 10.3390/ijms19102966

 See also: 

(8) Air Quality Inside Hospital – What Do our Doctors Say about It. 


(10) Staff are as important to the viability of health organisations as patients. The staff for these organisations is made up of people with very different professional backgrounds, such as doctors, nurses, home economics, maintenance and administration specialists, etc. The indoor environment has an impact on productivity, morale, health and well-being – and ultimately on the retention of staff in an organisation. For example, a study by the Lawrence Berkeley National Laboratory found that an improvement in IAQ improves employee productivity by 0.5 to 5% – a national impact on the workforce of $20 to $200 billion. These impacts provide health organisations with the incentive to improve the environment for their employees, and here too the IAQ is part of this equation.


Cite this blog post
Jean Odermatt (2020, October 21). Thick Air (Part 3) – Indoor Air Quality, SARS-CoV-2 and Healing Processes in Hospitals. Learning from Corona. Retrieved May 18, 2024, from

Jean Odermatt

Prof. Jean Odermatt is sociologist and interior designer. He is a professor emeritus at Bern the University of the Arts (HKB). His research focus is on how interior design can promote the process of recovery.

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