Good Air - Quality, Measurement and Certification

Explorative chapter. Brainstorming ideas how to provide and ensure good air. The associated health benefits including reduced Covid spread are sketched.

• Introduction
• Indoor Air Humidity and Temperature
• Exposure to Air Pollutants
• Air Quality Certification
• Use Cases
• Summed up Benefits of Good Air

Introduction

Covid demonstrates the importance of the air we breath:

• Covid mainly spreads well if the air is not well ventilated/cleaned.
• Severe Covid mainly spreads well if the air is dry.
• Severe Covid prevalence is increased in regions with a history of air pollution.

Epidemiological evidence is described in the Spread Analyses chapter and the underlying mechanisms in the Transmission chapter.

In this chapter methods to supervise the air quality and tools to achieve good air quality are discussed. The focus is on the following benefits:

1. Support the overall health by increasing the air quality
2. Reduce the transmission of severe Covid.
3. ‘Good Air Certification’ which helps to achieve (1.) & (2.). Background: Sometimes indoor room entry is only allowed with a ‘Covid certificate’ with the intention to allow only the entry of people who presumably exhale less infectious SARS-2 aerosol. Often it is assumed, that this is the case for tested/vaccinated or sometimes vaccinated only persons. An alternative is to certificate the air quality directly without the detour of entry restrictions.

Indoor Air Humidity and Temperature

To reduce the transmission of Covid the air is ideally above 25 degrees and has a high humidity and a CO2 value close to the outdoor air value. However there are tradeoffs between these transmission constraints themselves, the comfort (air at around 22 degrees and 45% humidity is often assumed as comfortable) and the ‘weathering’ of buildings (e.g. humid air -> condensation -> walls get mold).

• Warm Settings: The prevention of the spread of severe Covid is simple when the air is warm and humid: Opening the windows and turning off air-conditioners. The comfort can be decreased however. So a compromise would be to adjust the air to a temperature of around 27 degrees to a humidity of around 60%.

• Cold Settings: In cold climates it is tricky to achieve a good balance between a comfortable temperature (around 20 to 22 degrees), high ventilation (low CO2) and high humidity (much H2O). 1) Permanently opening the windows is usually not an option for comfort reasons. 2) Even if the temperature comfort is reached with good ventilation combined with heating, heating reduces the relative humidity - in other words the air dries when heated. So when heating there is a tradeoff between low CO2 values and not very dry air indoors. Solutions are: ventilation combined with humidification or cleaning the air to reduce the need for ventilation.

Exposure to Air Pollutants

The short and long term exposure to air pollutants is relevant for the susceptibility to severe Covid and also influences the overall health:

• The Covid death rates are higher in regions which regularly have high air pollution.
• Air pollution is generally relevant for susceptibility to respiratory infections.

• Air pollution can affect health in many ways e.g. increase the risk of arteriosclerosis which is risk factor for severe Covid.

  This page about betacoronaviruses is mostly written in settings with clean air: In regions of Swiss Alps and pre alps and some parts - in 2020 - also in the Austrian and Italian alps. Important basics were layed when working on islands and in coastal regions. Subjectively, I can better concentrate and have a better endurance in settings with good air.

Air Quality Certification

Different properties of the air we breath can be measured:

Property | Measured by | Influenced by | Relevance –|–|–|– Humidity | Humidity sensor | humidifier, heating combined with ventilation, AC| In dry air: lower clearance of the respiratory tract, increased survival of viruses , dry particulates have a higher deposition in the deep lungs Temperature | Thermometer | heating, ventilation, AC |comfort CO2 content | CO2 Sensor| ventilation, breathing | How much air is ‘re-breathed’ which is associated to the transmission of respiratory tract infections Particulate content | particulate sensor | outdoor air quality, ventilation, humidity, indoor particle sources, air cleaners| Cleanness of the air indicates possible infectious aerosol and air pollutants/allergens.

Use Cases

Well adjusted air in indoor rooms/businesses (hotels, restaurants, shopping malls) helps to:

• Reduce the overall burden of respiratory diseases.
• Support a good customer experience and can marketed (especially if measured/certified).

The optimal values and methods to achieve them depend on the settings:

• Very strong ventilation can cause some noise, air streams and possibly lower the temperature.
• Air cleaning can cause some noise.
• Higher humidity and temperature values, which reduce the virion viability and the risk for severe infections, are comfortable in some settings while not in other settings.

E.g. in fitness studios fresh and clean air is important due to deep inhaling, not only for Covid but for all pathogens and dirt particles. Ventilation and air cleaning are probably adequate options since some noise and some air stream are ok. When really really necessary, maxed ventilation should be possible even in winter since lower temperatures (e.g. 17 degrees) likely are tolerated as long as the customers are prepared.

Summed up Benefits of Good Air

Properties of the air we breath are determinants for the spread of Covid but also for the spread of many other respiratory diseases. Additionally pollutants can be health hazards and allergens cause discomfort. All in all, ‘good air’ has beyond Corona many benefits.