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In our previous post we wanted to put light on indoor air, and why we should care about it. Good indoor air keeps you healthy, and makes you feel, perform and sleep better. Those are quite good reasons to keep an eye on air quality.

So, what is good air? And how do we know if the air we breathe is good or bad? When it comes to water we can both see it and smell it. And we can definitely notice when there is a water leak. But air, we can’t even see…and our theory is that that’s why we don’t care that much about indoor air. So one of our tasks is to visualize the invisible. Thanks to digitization and sensor technique we can now measure different parameters in indoor environments, and then we actually can visualize air and find out what the air quality is! Great, isn’t it?

Let me start by introducing you to some parameters that we believe are important to measure to understand if the air quality in a room is good or bad.


Temperature is one of the main factors that determines how comfortable you feel inside your room or your office. To stay comfortable you would want to try to maintain a temperature range indoors from 21-26 degrees C. For offices and housing, a suitable indoor temperature in the summer is 23-26 C, and 20-24 C in the winter. The fact that it should be warmer in the summer is because the difference between outside and indoor temperature becomes too great otherwise. Wearing summer clothes mean that we would freeze indoors if we didn’t raise the temperature slightly.

However, how you experience temperature varies from one individual to another, depending on for example body temperature, activity type/-level, humidity level, and clothes worn. These factors will be presented in a separate blog post later on.

Relative Humidity (RH)

Relative humidity is the amount of moisture present in the air. It is dependent on temperature as warm air holds more moisture than cold air. Optimal RH is from 40% to 60%.

When it goes below 30% you may experience irritated mucous membranes, dry eyes and sinus discomfort. When it goes above 60% the presence of moisture and dirt can cause mould and other biological contaminants to thrive. RH levels that are too high can contribute to the growth and spread of unhealthy biological pollutants. Inhaling or touching mould can cause hay fever-type symptoms such as sneezing, runny nose, red eyes and skin rashes. Mould can also trigger asthma attacks. And too much humidity can of course also cause damage to the building.

Carbon Dioxide (CO2)

Carbon dioxide accumulation indoors is normally related directly to the number of occupants. Non-living sources of the gas may include space heaters, clothes dryers, stoves, or any other unvented gas-burning appliance. It is measured in parts per million, ppm.

400-800 ppm is the ideal state when you would feel comfortable.

800-1500 ppm – at this level, you would feel slightly drowsy and you would notice that the air is stale. It has no health effects, but it’s recommended not to not let it go beyond this range.

Higher levels of CO2 can cause common symptoms such as headaches, an increasing pulse rate, uncharacteristically high fatigue, decrease in productivity / cognitive thinking skills, poor concentration, slight nausea, and breathing difficulties.

The best way to reduce CO2 is to increase the airflow by turning up the ventilation system. If that’s not possible, opening doors or windows to let the CO2 out is the easiest way. Today ventilation- and indoor climate systems often are demand controlled. This means that the air flow adapts automatically depending on how many people are in the room.

Volatile Organic Compounds (VOCs)

VOC are carbon-based chemicals that are emitted as gases from solids or liquids. Some VOCs we can smell when there are high levels, others have no odour. There are thousands of different VOCs produced and used in our daily lives such as household products (paint, wood preservatives, aerosol sprays, cleansers and disinfectants, moth repellents and air fresheners, etc) and from activities at home (cooking, dry cleaning, smoking, wood burning stoves, etc).

The risk of health effects from inhaling any chemicals depends on how much is in the air, how long and how often a person breathes it in. Several studies suggest that exposure to VOCs may make symptoms worse in people who have asthma or are particularly sensitive to chemicals. Short-term effects include eye, nose and throat irritation, headaches, nausea, worsening of asthma symptoms. Long-term exposure increases risk of cancer, kidney damage and nerve damage.

Particulate Matter (PM 10, 2.5, 1)

These are fine dust particles or droplets in the air that vary from 10, 2.5, 1 microns or even less in width. To put it in context, there are about 10,000 microns in a cm. New research indicates the smallest particles in the air are the most dangerous. People with breathing and heart problems, children and the elderly may be particularly sensitive.

PM10 are big enough to be stopped when entering the throat. PM2.5 are dealt with in the lungs, while PM1 are small enough that the body cannot filter them when inhaled and thus enter our lungs, penetrate into the blood stream and can cause serious health effects. By using filters a majority of the particles from outside can be removed, and focus should of course be on filtering particles that are 1 μm (micrometre) or smaller in diameter – PM1.

Outdoor particles primarily come from cars, trucks, and other vehicles, while indoor particles come from tobacco smoke, cooking (e.g. frying, sautéing, and broiling), burning candles or oil lamps, and operating fire places etc. These are everywhere especially on carpets, stuffed toys, upholstered furniture, pillows, blankets and other beddings.

Dust levels above 100 microns/m3 may cause some short-term health effects such as eye, nose, throat and lung irritation, coughing, sneezing, runny nose and shortness of breath. If you have chronic respiratory conditions such as asthma, rhinitis or bronchiolitis and dust is one of the things you’re sensitive to, particles can affect your lung function and worsen your asthma. If you are sensitive, make sure that your home is kept clean and dust free. Also vacuum your carpets, upholstered furniture, pillows, blankets and beddings. Remember to check your child’s stuffed toys for dander or dust mites, these could be the ones causing his/her respiratory conditions. You may also consider buying an air purifier with HEPA filters.


Wow, that was a lof of information. And I could go on and on about good indoor air. But, I will make a pause here.

If you feel that you really want to nerd into this, you can visit the RESET™ Standard web. They have a lot of good information on sensors, monitoring, and healthy air. RESET combines the development of live monitoring and cloud software to increase the visibility of building health data.

Questions, or up for a chat? Drop us a line or give us a call!