The most basic indication of indoor air quality is its temperature: you immediately sense if it’s ‘too hot’ or ‘too cold’. Temperature is important for indoor air quality:

  • Temperature and sense of well-being
  • Humidity
  • Spreading of Covid-19 and other viruses

Temperature and sense of well-being

The most basic indication of indoor air quality is its temperature: you immediately sense if it’s ‘too hot’ or ‘too cold’. And it immediately affects your sense of well-being. Extreme heat is a serious risk for your health ((Healy 2003, Kosatsky 2005). Besides, high temperatures can cause insufficient humidity (Reinikainen and Jaakkola, 2001).

How does Temperature Affect the Spread of Viruses

Since Covid-19, there is more attention for the strong influence of temperature on the spread and activity of viruses. Viruses that cause respiratory infections often occur in the winter. This may be caused due to reduced resistance of the so called ‘mucous membranes’ in the nose when cold air is inhaled (Frank van Kuppeveld, professor virology, University of Utrecht). A temperature of 19°C  to 24°C (66°F to 75°F) helps you to prevent the drying of your nasal passage. So that you are less susceptible to viruses.

FIG. 1. Survival of TGEV and MHV at 4°C and (a) 20% RH, (b) 50% RH, and (c) 80% RH. Squares, TGEV; circles, MHV. The error bars indicate 95% confidence intervals. How temperature and humidity have effect on survival of virus

Research by Lisa M. Casanova et al shows that the infection rate of viruses is significantly reduced when the temperature indoors at room temperature (20°C or 68°F) compared to colder temperatures (4°C or 39°F). However, when the temperature is warmer (30°C or 86°F), the transmission of influenza viruses is blocked or becomes very inefficient (Effects of Air Temperature and Relative Humidity on Coronavirus Survival on Surfaces, Lisa M. Casanova et al, Applied and Environmental Microbiology, May 2010)

But of course, many people don’t find an indoors temperature of 30°C comfortable. To maintain your indoor temperature at room temperature makes you feel comfortable. It also lessens the risk of virus transmission.

Temperature, Humidity and Covid-19

Temperature and humidity go hand-in-hand. Research shows, that the Covid-19 virus can survive several hours and even several days on surfaces.

Of course, the greatest spread of the virus is via ‘direct’ contact: not keeping the physical distance, so that the virus is transmitted via the large droplets via talking, coughing or sneezing.

The WHO mentions that people can be infected with Covid-19 by touching their faces after they have touched contaminated objects and surfaces (WHOS’s Guide for Worker Safety, March 2020).  

In general, infections via surfaces and then touching your face appear to be the least of threats to spread Covid-19. It is uncertain how much people get infected by Covid-19 via air: do the so-called ‘aerosols’ contain enough virus to get someone ill? Poor conditions of ventilation may play a part. Of course, there are already some new variants of the virus, such as the British variant, which have more virus material in the droplets.


The ‘Alara’ principle is a sound mechanism. This means: the As Low As Reasonably Achievable principle.  It is always good to lessen risks.  Spread of the Covid-19 virus via contaminated surfaces or air may not (or may) the most principal risk… but it means there is still risk. Besides, an optimal environment helps to lessen the spread of other viruses and is good practice of hygiene.

Solutions like the Covid Airmex can help you to monitor your temperature, humidity, tvoc and co2, for a safe and healthy working environment


For feeling comfortable indoor, humidity is one of the most important factors, both physical and mentally. Where temperature is immediately perceived (‘cold in here’), humidity is also one of the most important factors for feeling comfortable indoors. Besides, temperature and humidity go hand-in-hand. Besides, humidity plays a factor in the growth of molds and other allergens.

Indoor air humidity

Humidity is the concentration of water vapor present in the air. Humidity depends on the temperature and pressure. Warm air is able to bind more water than cold. The same amount of water vapor results in higher humidity in cool air than warm air. So, humidity is also important how we experience the temperature. Many measurements of humidity consist of relative humidity: how much water there is in the air relative to the maximum of water it can contain given the same temperature. Regulation the indoor humidity and temperature goes together.

Effect of humidity on well-being and health

Humans are more sensitive to changes in temperature than in relative humidity. However, humidity is an important factor in thermal comfort: the condition of mind that expresses satisfaction with the thermal environment. Outdoor, humidity has a much stronger influence at higher than at low temperatures.

Human bodies use evaporative cooling to regulate temperate as primary mechanism. The rate of which perspiration evaporates on the skin is under humid conditions lower than in arid ones. Humans feel warmer at a relative high humidity, because humans perceive the rate of heat transfer from the body rather than the temperature itself.

High humidity (‘humid air’) or low humidity (‘dry air’) can have negative effects on well-being and health. You can feel some effects immediately and they disappear when the humidity is adjusted (or when you leave the room), some effects may rise years later.

Effects of dry air

Dry air may cause:

  • Dry eyes
  • Chapped lips
  • Bloody nose
  • Itching of the nose
  • Irritation of the skin
  • Allergy problems and asthma

Dry air during winter

You have probably experienced yourself: at winter, indoor air quality is often rather dry. When temperature decreases under 0°C, relative humidity can drop to 20%. However, ‘good’ indoor humidity should be between 20 and 40%. The cause of dry air is often the room temperature. That’s why room temperature should be kept under 22°C (72°F).

Humid air

Some effects of humid air indoor:

  • Fatigue
  • Frizzy hair
  • Feeling hot or sweaty
  • Sleep interruptions
  • Respiratory problems
  • Allergy problems and asthma

Humid air during summer

During summer, the ideal indoor humidity is between 30% to 50%, following the high humidity outside. In any case, constant humidity must be kept under 60%, to prevent the growth of microbes.

Humid air during winter

In some cases, the indoor humidity may rise above 45% during winter. Mostly this is caused by human activity with poor ventilation. The most immediate visible effect is condensing on cold surfaces as windows. When there is often the case of humid air, condense may affect the structure of the building and can cause health problems.

Solutions like Airmex can help you to monitor your humidity, for a comfortable, safe and healthy working environment.


Did you ever wonder where you are most exposed to air pollution? Somewhere outside, you say? Wrong, you breath the most polluted air… indoors! Research shows, that people spend 90% of their time indoors. Isolation and modern heating have brought us comfy, warm indoor environments: home, work, recreation, etc., with no cold air coming from under the doors. However, in many buildings there is a downside. With the tightly enclosed indoor environments, pollution caused indoors or coming from outside has no opportunity to mingle with fresh air. For viruses, heat and certain levels of immunity are perfect environments to stay active. Besides, the Covid-19 virus is spreading.

Indoor concentration of pollution often 2 to 5 times higher than outdoor

Research on the United States Environmental Protection Agency (EPA) site shows:

  • “Americans, on average, spend approximately 90 percent of their time indoors,1 where the concentrations of some pollutants are often 2 to 5 times higher than typical outdoor concentrations.2
  • People who are often most susceptible to the adverse effects of pollution (e.g., the very young, older adults, people with cardiovascular or respiratory disease) tend to spend even more time indoors.3
  • Indoor concentrations of some pollutants have increased in recent decades due to such factors as energy-efficient building construction (when it lacks sufficient mechanical ventilation to ensure adequate air exchange) and increased use of synthetic building materials, furnishings, personal care products, pesticides, and household cleaners.”

Why is air quality important?

You probably know the irritation of eyes or a dry troath yourself. Indoor air pollution can have serious health effects, ranging from irritation of your eyes to respiratory diseases:

  • Irritation of the throat, nose and eyes, such as a dry throat
  • Headaches, dizziness, and fatigue
  • Respiratory diseases, heart disease, and cancer

Indoor concentration of pollution often 2 to 5 times higher than outdoor

“The link between some common indoor air pollutants (e.g., radon, particle pollution, carbon monoxide, Legionella bacterium) and health effects is very well established.

  • Radon is a known human carcinogen and is the second leading cause of lung cancer.4, 5
  • Carbon monoxide is toxic, and short-term exposure to elevated carbon monoxide levels in indoor settings can be lethal.6
  • Episodes of Legionnaires’ disease, a form of pneumonia caused by exposure to the Legionella bacterium, have been associated with buildings with poorly maintained air conditioning or heating systems.7, 8
  • Numerous indoor air pollutants—dust mites, mold, pet dander, environmental tobacco smoke, cockroach allergens, particulate matter, and others—are “asthma triggers,” meaning that some asthmatics might experience asthma attacks following exposure.9

While adverse health effects have been attributed to some specific pollutants, the scientific understanding of some indoor air quality issues continues to evolve. …

One example is “sick building syndrome,” which occurs when building occupants experience similar symptoms after entering a particular building, with symptoms diminishing or disappearing after they leave the building. These symptoms are increasingly being attributed to a variety of building indoor air attributes.

Researchers also have been investigating the relationship between indoor air quality and important issues not traditionally thought of as related to health, such as student performance in the classroom and productivity in occupational settings.10

Solutions like the Covid Airmex can help you to monitor your temperature, humidity, tvoc and co2, for a safe and healthy working environment