There are a number of ways humidity causes damage in your building because its level is too high, as:

  • Look for signs of allergies from anyone in the building such as worsening hay fever sneezing or post nasal drip
  • Fog on indoor windows
  • Mold growth; moldy or dusty smell
  • Damp spots, e.g., on ceilings or walls
  • Peeling paint
  • Sweating on the basement floor or walls
  • Condensation on water pipes
  • Any collection of water or mildew
  • Decaying wood
  • Wet spots or water stains on ceilings

For most indications that the humidity is too high, the ‘symptoms’ manifest themselves over a long time, e.g., damp spots and peeling paint. For your assets, the saying goes ‘prevention is better than to cure’. Walls and windows have to be painted again, rotten wood has to be replaced, etc.

And even more important, this means that people inside the building have long suffered from humidity levels that are too high. For many people, it has deteriorated their feeling of well-being and worsened their productivity. It may also have triggered and worsened asthmatic and allergenic symptoms.

How to prevent indoor air gets too moist?

Check your indoor air quality and take care of the humidity. The EPA (Environmental Protection Agency) advises to keep humidity levels between 30–50%. Modern sensors like the AirGuard measure humidity, heat and TVOC and CO2 as well and give you a warning when humidity conditions are not optimal. So, you can open or close a window for instance.

For many, Covid-19 was an eye-opener for the importance of indoor air quality. Children spend a large portion of the day at school. American research shows, that children spend 1000 hours at school every year.It is therefore very important that students and teachers stay in a room with clean air. It is healthier and more pleasant. And poor air quality causes students to get worse grades. Why is good indoor air quality in schools and properly functioning HVAC so important? And how can sensors help monitor indoor air quality?

Lower grades, less fun

With stale air, students may find it hard to pay attention to the teacher. Or concentrate on tests or stay awake at all. Besides, poor indoor air quality may affect the ability to make decisions. So, without even realizing yourself, it can damage your productivity and your school results.

Research at K-12 education by Jacqueline M. Nowicki  (U.S. Government Accountability Office, K-12 Education: School Districts Frequently Identified Multiple Building Systems Needing Updates or Replacement., Jacqueline M. Nowicki, June 4, 2020) shows that: “compelling evidence…of an association of increased student performance with increased ventilation rates,” yet “ventilation rates in classrooms often fall far short of the minimum ventilation rates specified in standards.” 41% of U.S. school districts  need to update or replace their HVAC (heating, ventilation and air conditioning) systems in at least half of their schools. This means about 36,000 schools in the US.

In a survey of school buildings in the Netherlands, 7340 school buildings responded, but not always completely. Overall, 38% of the responding schools met the requested standards, that is 2789 schools. 807 schools (11%) indicated that they did not meet. The remaining schools could not (yet) say whether their building met the standards.

Further, a bad indoor air quality may lead to headaches and cause or worsen asthma and other respiratory illnesses. And, of course, it’s more pleasant to be in a classroom with clean air. Especially when you spend most of the day there.

How can you improve your indoor climate?

4 steps to improve Indoor Air Quality at schools

  1. Install and improve HVAC
  2. Filter and clean the air
  3. Measure indoor air quality with sensors
  4. Dashboard: monitor your indoor air quality

Install and improve HVAC

Due to poor ventilation, the ‘used’ air will not dilute enough with ‘new’, fresh air from outside. So, especially with many people in a closed room (like a class-room) and the ventilation is poor, the fresh air in this room gets more and more replaced by stale air. That’s why effective ventilation requires that it both brings fresh, oxygenated air from outdoors and removes stale indoor air.

sensors indoor air quality classroom Airguard

How to adjust HVAC within schools:

  • If you haven’t done already: install proper HVAC
  • A California study shows that 85% of the classrooms did not provide adequate ventilation
  • Purify the air in the building by extending the operating times of HVAC systems. Let the HVAC run before the first staff arrives and also after the last persons have gone home
  • Increase the rate of air exchanges to provide fresh air through natural of mechanical ventilation
  • Increase to 100% of fresh air intake or the maximum amount possible

Besides, regarding COVID-19, recent study (Centers for Disease Control and Prevention) shows that Covid-19 was 39% lower in schools by opening windows and doors, using fans, or those measurements in combination with air filtration methods.

Filter and Clean the Air

Air cleaners and HVAC filters filter pollutants or contaminants out of the air that passes thru them. They can help reduce airborne contaminants, including particles containing viruses. When ventilation with outdoor air is not possible or when outdoor air pollution is high, air purifiers (portable air cleaners) may be helpful without worsening comfort (temperature or humidity).

Sensors measure Indoor Air Quality

Children spend many hours indoors at school. Therefore, it is important to have a good indoor air quality. For the feeling of well-being for the children and teacher, but also for the children’s grades. You can measure the CO2 with a CO2 meter, or a sensor which combines the monitoring of CO2 with temperature, humidity and Volatile Organic Compounds, for instance ASN Airguard.

If you have installed HVAC, in some cases this doesn’t work properly. This may be caused by:

•             Problems with installation of HVAC systems

•             Incorrect HVAC systems purchased

•             Incorrect controls and thermostats

•             No follow-up testing after installation

•             Poorly-maintained filters

Besides, when you’re busy, keeping an eye on the air quality may easily be ignored. Sensors warn you that the indoor quality has worsened. And they help you to maintain your indoor air quality such, that the risk of spreading the viruses is as least as possible. These warn you with a signal on the sensor and an alert on your app. So, you can take action, adjust your HVAC or just open a window.

Indoor air qualities sensors monitor your indoor climate. They monitor CO2, TOVC, humidity and temperature.

Dashboard: monitor your indoor air quality

Monitor the indoor air quality of your school with a dashboard. You can monitor humidity, temperature, TVOC and CO2 in real time. And it shows how the school performs over time: are there any locations where the indoor air quality easily drops to an unwanted level? So, you can find out the causes and improve air quality.

It is not only schools themselves that are increasingly recognizing the importance of a good indoor climate for students and teachers.  But more and more governments (and parents) are also aware of the importance of air quality within schools. Through monitoring, schools can show authorities that they are meeting air quality standards. And also show parents that they provide a healthy and pleasant learning environment for their children.

Further, facility managers can use their reports by optimizing and save on energy costs by use of energy based on occupation levels and other factors.

For many, Covid-19 was an eye-opener for the importance of indoor air quality. One of the most important pollutants indoors is Carbon Dioxide (CO2). Children spend a large portion of the day at school. Research shows that there are high levels of CO2 in many classrooms. Those high CO2 levels affect the sense of wellbeing, and even worse: school grades.

CO2 levels in school too high

The Western Cooling Efficiency Center (UC Davis ) shows: “Research from around the world shows there are high CO2 levels in many classrooms. For example, in a 2019 study, researchers found that about 85% of 94 recently installed HVAC systems in California K-12 classrooms did not provide adequate ventilation.”They investigated 104 classrooms in California. 85% did not have proper ventilation, which means increased levels of CO2.

In indoor testing between 2010 and 2015, 43% of Toronto schools had a CO2 concentration above 1000 ppm.

Why does the last hour always take ages?

bored child classroom school high co2 levels airmex

After sitting the whole day at school, the last hour seems to take ages. Always getting a headache. You can’t concentrate and think properly. Probably the cause it isn’t the teacher. It’s you, the students.

Students and the teacher breathe oxygen into the lungs as energy. The oxygen sticks to red blood cells and is transported to organs and muscles, so your heart can pump, you can think with your brain and contract your muscles. This ‘burning’ process of oxygen turns into carbon dioxide (CO2) and water vapor, which are released back into the environment.

When the ventilation is poor, the ‘used’ air will not dilute enough with ‘new’, fresh air from outside. So, especially with many people in a closed room (like a class-room) and the ventilation is poor, the oxygen in this room gets more and more replaced by CO2.

CO2 itself is not toxic. In fact, it’s a natural part of the atmosphere. It’s the fact that it’s replacing the oxygen concentration because a high concentration of CO2 is toxic. (That’s why CO2 is called an ‘asphyxiant gas’:  a nontoxic or minimally toxic gas which reduces or displaces the normal oxygen concentration in breathable air.)

How CO2 levels affect school results

Due to the fact that the student inhales less oxygen, less oxygen goes to the brains. If there’s too much CO2, students may find it hard to pay attention to the teacher. Or concentrate on tests. Or stay awake at all. Besides, high levels of CO2 may affect the ability to make decisions. So, without even realizing yourself, high CO2 can damage your productivity and your school results. Besides, when we think of gasses, we think smell will warn us. However, CO2 is odourless.

CO2 might also cause physically complaints:

  • Headache
  • Feeling dizzy or nauseous
  • Tired
  • Trouble breathing
  • Worsen asthma symptoms, allergies and lung health

You yourself might feel complaints, while the student next to you doesn’t feel anything. How you react, depends on several factors – such as: your own health, heredity, personal habits as smoking and drinking, use of medicine, previous exposure to chemicals.

What are high CO2 Levels?

As said, CO2 is a gas that is a natural part of the air. CO2 is measured in so-called parts per million (ppm). Outside, the normal level is about 400ppm. Otherwise said: per 1 million parts in the air, 400 of them consists of carbon dioxide. Before the industrial revolution, this level was about 280 ppm.

In general, occupied rooms with good ventilation have 400 – 1,000ppm. However, from 800 ppm, people may begin to suffer, maybe without knowing themselves.

From 1,000 to 2,000 ppm, people get complaints of drowsiness and poor air. When the level is between 2,000 to 5,000 ppm: complaints of headaches and sleepiness. The air becomes stale, stagnant and stuffy. As a consequence, people have lower concentration and loss of attention. An increased heart rate and slight nausea may also be the case.

From more than 5,000 ppm, the air becomes toxic and more serious effects can occur.

Common HVAC Issues resulting in high CO2 levels

In modern times, schools and other buildings are built with comfort in mind: to create a comfortable, warm space, thanks to isolation and… However, this comfort may come with a downside. Because a room is too closed from the outside world, this may result in the lack of replacing the air inside with fresh air from outside.

In the California study, 85% of the classrooms did not provide adequate ventilation. ‘“We were shocked,” said Wanyu Rengie Chan, one of the lead researchers of the study, “We were not expecting it.”’ They were shocked, because it involved classrooms with newly installed HVAC.

What are HVAC issues, causing high CO2 levels?

  • Problems with installation of HVAC systems
  • Incorrect HVAC systems purchased
  • Incorrect controls and thermostats
  • No follow-up testing after installation
  • Poorly-maintained filters

(Source: Ventilation Rates in California Classrooms study)

CO2 monitoring helps

Children spend many hours indoors at school. Therefore, it is important to have a good indoor air quality. For the feeling of well-being for the children and teacher, but also for the children’s grades. You can measure the CO2 with a CO2 meter, or a sensor which combines the monitoring of CO2 with temperature, humidity and Volatile Organic Compounds, for instance ASN’s Covid-AIRMEX.

Advanced Solutions Nederland’s AIRMEX employs the Nordic Thingy:52 to provide easy-to-use environmental sensors and wireless connectivity for pandemic management

Nordic Semiconductor today announces that Amersfoort, Netherlands-based, Advanced Solutions Nederland (ASN), an IoT and Industrial IoT (IIoT) sensor technology company, has selected the Nordic Thingy:52 Bluetooth® 5.2/Bluetooth Low Energy (Bluetooth LE) compact multisensor prototyping platform to provide the wireless connectivity and processing power for its ‘AIRMEX’ indoor environmental monitoring solution. AIRMEX is an AI-powered temperature, humidity, CO2, and TVOC (Total Volatile Organic Compounds) sensor platform that enables, for example, workplaces, schools, restaurants, and places of worship to monitor and regulate indoor environmental conditions to minimize the risk of the airborne spread of SARS-CoV-2, the virus that causes Covid-19, as well as promote overall healthy living and working conditions for occupants.

This article is retrieved from Nordic Semiconductor: original publication, 04Mar 2021 Oslo, Norway)

Recommendations for air-quality improvement

The ceiling- or wall-mounted device employs the Nordic Thingy:52’s integrated humidity, temperature and gas sensors to provide continuous, near real time monitoring of environmental air quality. Running ASN’s ‘Chameleon’ AI algorithmic application software—developed and ‘trained’ to promote indoor air conditions that specifically minimize the risk of the spread of Covid-19—the Nordic Thingy:52’s powerful 64MHz, 32-bit Arm® Cortex® M4F processor with floating point unit (FPU), allows the solution to process the data from all four sensor. The applications software does more than simply measure and display temperature and humidity readings, rather it provides real-time updates and recommendations for air quality improvement.

The Nordic Thingy:52 integrates many useful sensors which along with its Bluetooth LE connectivity provides a cost-sensitive solution

Dr Sanjeev Sarpal, ASN

The data is relayed to a Bluetooth 4.0 (and later) smartphone, where from the partner ‘Covid-AIRMEX’ Android app, the user is provided with immediate feedback on overall air quality and recommendations on how to improve the environmental conditions. For example, “increase dehumidifier settings” to reduce humidity, or “very high gas levels present” to indicate inadequate ventilation. In the absence of a smartphone, AIRMEX has a multi-coloured LED indicator to provide users with an immediate overview of current environmental conditions.

AIRMEX uses a standard 1400mAh Li-ion battery to provide approximately six weeks battery life in standard operation, thanks in part to the ultra-low power characteristics of Nordic’s nRF52832 System-on-Chip (SoC) at the heart of the Nordic Thingy:52. The nRF52832 has been engineered to minimize power consumption with a fully-automatic power management system that reduces power consumption by up to 80 percent compared with the nRF51 Series. 

Multisensor prototyping platform

The Nordic Thingy:52 is a compact multisensor prototyping platform designed to help wireless IoT sensor projects get off the ground quickly. The product is a fully tested and working wireless sensor platform that can be used by a developer with no high-level development tools or firmware coding expertise to rapidly design wireless IoT devices and associated mobile device and Internet apps. The Nordic Thingy:52 is based on the nRF52832 SoC. The SoC features a 32-bit, 64MHz Arm® Cortex™ M4 processor with a 2.4GHz multiprotocol radio (supporting Bluetooth 5.2, ANT™, and proprietary 2.4GHz RF protocol software) featuring -96dB RX sensitivity, and 512kB Flash memory and 64kB RAM. The SoC runs Nordic’s S132 SoftDevice—a Bluetooth 5-certifed RF software protocol stack for building advanced Bluetooth LE applications—it can support up to 20 concurrent connections in a variety of Bluetooth LE role combinations.

“The Nordic Thingy:52 integrates many useful sensors which along with its Bluetooth LE connectivity provides a cost-sensitive solution,” says Dr Sanjeev Sarpal, Director AI Data Algorithms & Analytics at ASN. “The well written firmware libraries also helped our developers get up and running in a fraction of the time rather than starting a development from scratch, while the reference designs and good documentation were equally an important consideration in selecting the solution.”

Since Covid-19, there is even more attention for indoor air quality. It might be possible that poor ventilation may contribute to the spread of the coronavirus. In any case, some contaminations are already known to decrease indoor air quality. Poor Humidity, Temperature, CO2 and TVOC conditions may be the cause. It influences productivity, leads to less sense of comfortability and well-being and can cause sickness. Beat poor indoor Air Quality with data science.

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

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 or through windows. 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 humidity are perfect environments to stay active.

Pollution may lead to:

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


Besides, the Covid-19 virus is spreading. Since Covid-19, there is a lot of attention for indoor door quality. Besides social distancing, wearing a mask and washing your hands, good ventilation is one of the measures to reduce the risk of infection indoors.

CO2 and TVOC measurement for well-being and productivity

Indoor air quality is depending on… inside and outside factors… Besides temperature and humidity, 2 other factors for indoor air quality are CO2 (Carbon Dioxide) and TVOC (Total Volatile Organic Compounds).

CO2 originates when people breathe, sweat and in all other occasions where there is a burning process involved. CO2 concentration has to remains less than 800 PPM. At higher concentrations people begin to suffer.

Besides, many substances are also source of contamination like cleaning products, paints, varnishes, furniture and glues. These are called Volatile Organic Compounds (VOC’s). Immediate complaints may be symptoms headaches, eye, nose and throat irritation and bad odors. Long term exposure may lead in large doses can damage liver, nervous systems and kidneys.

The impaction of the combination of CO2 and TVOC is even larger. A study shows: “On average, cognitive scores were 61% higher on the Green building day and 101% higher on the two Green+ building days than on the Conventional building day.” 

Data Science helps you to maintain healthy and productive air quality

Temperature and Ventilation are more important than ever. Regulate your temperature to obtain a comfortable and healthy environment. Replace bad air with fresh air from outside. By ventilation or just by opening a window.

When you’re busy, keeping an eye on working conditions may be easily ignored. Sensors which measure temperature and humidity like the Airmex help you to maintain your indoor air quality such, that the risk of spreading the viruses is as least as possible They also help you to keep a comfortable, healthy and productive environment. It warns you on an app when you should adjust your room temperature or when you should ventilate. Those signals are based on data science and based on guidelines as the ASHRAE Standard 55 – Thermal Environmental conditions for Human Occupancy.

Find out how the Airmex can help you.

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

When we think of air quality, people mostly think of the outside world, smog from cars and industry or the fresh air of woods. However, 90% of our daily life is spent indoors: our home, workplace, public buildings and schools. Indoor quality is one of the most important components of well-being, feeling comfortable in a room.  Besides, bad air quality has implications on your productivity and may even harm your health. The Volatile organic components (VOC) may be the least known.

TVOCS affects the wellbeing, feeling comfortable and health

TVOCs affect your sense off wellbeing and if you feel comfortable inside a building. Some VOC’s are even bad for health. Some VOCs are more harmful than others. If a TVOC is harmful also depend on factors as level of exposure and length of time being exposed. Besides, some people -especially children and elderly people- have a higher sensibility then others. Immediate symptoms that some people have experienced soon after exposure to VOCs are eye and respiratory tract irritation, headaches, dizziness, visual disorders and memory impairment. An example: some people get immediately a headache from being in a room which is just painted. Others may find the smell just uncomfortable.

TVOCs can cause:

  • Headaches
  • Dizziness
  • Nausea
  • Eye, nose, and throat irritation
  • Coordination loss
  • Fatigue
  • Some VOC’s (as toluene) cause irritation at normal levels, eg allergic skin reactions
  • Bad odor and stale air are uncomfortable and affect people’s feeling of cleanliness
  • Some VOC’s as formaldehyde can cause cancer. VOC’s for a long-term exposure in large doses can damage liver, nervous system and kidneys

What is TVOC?

What is TVOC? TVOC means Total Volatile Organic compounds. Volatile organic compounds are organic chemicals that become a gas at room temperature. There are thousands of VOCs and a multiple of VOC’s are at the same time present. Therefore, the Total VOC is used at most times: measuring the concentration of the total of VOC’s This is easier and less expensive then measuring individual VOC’s.

Some examples of VOC’s are:

  • Benzene
  • Ethylene glycol
  • Formaldehyde
  • Methylene chloride
  • Tetrachloroethylene
  • Toluene

Where do you find VOC’s?

VOC’s come from many sources, even yourself can be a polluter!

  • Products
  • Outside world

VOC in Products

Many VOC’s come from:

  • Cleaners and disinfectants
  • Pesticides
  • Air fresheners
  • Paints and solvents
  • Glue
  • New furniture and carpets
  • Construction materials
  • Electronic devices
  • Plywood

So, some VOC’s may come from everyday life, especially found in sprays and aerosols from cleaners and such. Besides, new construction and renovation may cause significant health concerns. Construction materials, but also the new furniture, carpets and plywood may increase the indoor concentration of VOC’s due to off-gassing. Until the off-gassing has declined, those new products may cause serious threats to your well-being. You can be a polluter yourself, however often far less dangerous then products do.

VOC in the outside world

Vehicle exhaust and indusstry pollution may also cause bad indoor air quality when the polluted air can enter the building due to open windows or air condition that doesn’t work properly. Especially when the building stands in congested or industrial areas.

Are all VOC’s harmful?

“EPA’s Total Exposure Assessment Methodology (TEAM) studies found levels of about a dozen common organic pollutants to be 2 to 5 times higher inside homes than outside, regardless of whether the homes were located in rural or highly industrial areas. Additional TEAM studies indicate that while people are using products containing organic chemicals, they can expose themselves and others to very high pollutant levels, and elevated concentrations can persist in the air long after the activity is completed.” (What are volatile organic compounds (VOCs)?, EPA,

TVOC can be measured in micrograms per cubic meter (µg/m3) of air (or milligrams per cubic meter (mg/m3), parts per million (ppm) or parts per billion (ppb)). The table below shows that less than 0.3 mg/m3 are considered low TVOC concentration levels. And levels between 0.3 mg/m3 to 0.5 mg/m3 are acceptable.

TVOC Level mg/m3Level of Concern
Less than 0.3 mg/m3Low
0.3 to 0.5 mg/m3Acceptable
0.5 to 1 mg/m3Marginal
1 to 3 mg/m3High
TVOC Level mg/m3 and Level of Concern

The ASN Airmex measures the TVOC in your building, for a safe and comfortable indoor air quality