How Is Indoor Air Quality Measured?

How Is Indoor Air Quality Measured featured photo

Do you ever wonder if indoor air affects your health? You are not alone. As someone who has been diagnosed with a respiratory infection, I want to know how indoor pollution impacts my comfort and well-being.

Determining indoor air quality is the first step to doing this. There are various ways to measure indoor air quality. The most common method is using sensors or monitors to assess pollutants in your home.

This article will show how each monitoring device can measure indoor air quality. But first, you will learn the importance of indoor air quality and the factors affecting it.

What Is Indoor Air Quality? And Why Is It Important?

Indoor air quality, or IAQ, is the quality of air inside a building or other enclosed structures. It encompasses both commercial and residential establishments, such as homes and apartments. 

Some individuals dismiss the importance of indoor air quality. However, the Environmental Protection Agency states that the average person spends 90% of their time indoors. In these enclosed places, pollutant levels are two to five times higher than outdoor concentrations. 

Indoor air pollution can ultimately affect the health and comfort of people. Poor indoor air quality also leads to a range of health problems, including respiratory issues, headaches, and fatigue. According to the World Health Organization, indoor pollutants can even increase the risk of premature death.

What Is the Acceptable Indoor Air Quality?

By now, you already know the importance of indoor air quality. But how do you know if IAQ is good enough without detrimental effects on your health?

Organizations like the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) and the U.S. Environmental Protection Agency (EPA) establish indoor air quality testing standards.

In particular, ASHRAE states that acceptable indoor air quality must be free of harmful contaminants at high concentrations. It must not result in odor and sensory irritation for 80% of individuals in the building. 

Meanwhile, the EPA offers guidelines for acceptable levels of indoor air pollutants. These include carbon monoxide, radon, and other volatile organic compounds (VOC). 

Regular air monitoring and maintenance is a must to improve indoor air quality.

What Affects Indoor Air Quality?

Various factors and substances affect indoor air quality. 

Pollutants are among the largest offenders. These include chemicals, gases, and other particles that can enter a building from the outside. They can also come from the inside, such as volatile organic compounds (VOCs) from cleaning products.

Indoor temperature and humidity are other factors causing indoor air quality problems. They support the growth of harmful bacteria and mold. Even indoor plants can harbor fungus and mold when not cared for properly.

Plus, poor ventilation leads to an increase in indoor air pollution. They can be harmful, especially if constantly exposed to these conditions.

On top of these elements, building materials, pests, and indoor occupancy can also impact IAQ. For instance, construction materials can emit pollutants, like formaldehyde, in particle boards, and VOCs from paint.

Meanwhile, pests produce droppings and urine. These are potential allergens that can cause health problems.Also, the number of people in a building space and their activities can affect indoor air quality.

In addition, there was a 1989 study done by NASA that concluded that indoor air quality is likely improved by plants. The chemicals trichloroethylene, benzene, and formaldehyde were greatly reduced in the study.

If you’re interested in adding indoor plants to your home, there are many you can propagate in order to save money. We have some guides for propogating string of pearls and peperomia, but there are many more than can be multiplied solely by purchasing one plant.

How Is Indoor Air Quality Measured?

You can measure air quality using various instruments and tools. These can help you identify harmful substances and other potential irritants in the air. It is the first step to improving indoor air quality.

Below, you will learn how these different devices test indoor air quality.

VOC Sensor

A VOC (volatile organic compound) sensor is exactly as it sounds—it measures the level of VOCs in the air.

To know why it is important to monitor VOCs, it is a must to understand these compounds. VOCs come from cleaning products, personal care products, and other household items. They have detrimental effects on indoor air quality and your overall health. 

A VOC sensor is built with a metal oxide semiconductor (MOS) or electrochemical cell. It can detect various particles, such as formaldehyde and ketones, inside your home. Once you determine the presence of these pollutants, it will be easy to reduce their harmful effects in your living spaces.

Carbon Dioxide Sensor

A carbon dioxide meter or sensor is originally designed for greenhouses. But with indoor pollutants becoming more prominent, this indoor air quality monitoring tool is now common among many residences.

Carbon dioxide (CO2) refers to the naturally-occurring gas exhaled by humans and animals. It also comes from burning fossil fuels and volcanic eruptions.

In general, small concentrations of CO2 are not highly toxic when inhaled. However, high levels of CO2 in indoor spaces negatively impact air quality and health. Individuals will have difficulty breathing and concentrating due to a lack of oxygen.

CO2 sensors can monitor carbon dioxide levels in the air through infrared (IR) absorption or non-dispersive infrared (NDIR) technology. Some models can also activate heating, ventilation, and air conditioning (HVAC) systems to give fresh air.

The only downside of this sensor is it can only detect human-expelled carbon dioxide. It is incapable of identifying dangerous gases.

Humidity Sensor

Humidity Sensor

Also known as a hygrometer, a humidity sensor calculate the amount of water vapor in the air. It comes in three different types: capacitive, resistive, and thermal. Each one can detect the smallest changes in the atmosphere to measure the humidity in the air.

High water vapor levels or too much humidity can negatively impact indoor air quality standards. The relative humidity (RH) must be between 40% and 60% to ensure comfort and healthy air quality.

MERV Rating

Indoor air quality can be measured by air filters using the Minimum Efficiency Reporting Value (MERV) Rating.

MERV is the standard for evaluating the effectiveness of air filters in HVAC systems. MERV ratings range from 1 to 16. The higher the value, the better they can filter harmful air particles.

For example, filters with a MERV rating of 14 to 16 can remove the smallest particles in the air. These make them suitable for hospitals, labs, and other sensitive environments. 

However, the highest MERV rating can reduce the airflow in the HVAC system. As a result, the motor consumes more energy and works harder to ensure a proper ventilation system. 

Choose the right MERV filter rating that matches your needs. Most homes can enjoy a healthy indoor environment with MERV ratings of 6 to 13.

How Do You Interpret Air Indoor Quality Test Results?

As there are various ways to measure indoor air quality, you can also interpret the results in different means. 

Unfortunately, it is not easy to set standards for indoor air quality monitoring. For instance, when someone has health problems, the illness can be caused by two or more pollutants. So even if you identified toxic levels of CO2 in your home with a carbon dioxide sensor, you could never be sure if it is the only cause.

That said, you can rely on indoor air quality testing professionals or health agencies to interpret IAQ results accurately. These can enable you to understand the cause of unhealthy air levels. 

How to Improve Indoor Air Quality?

How to Improve Indoor Air Quality

Once you have interpreted the IAQ results, you can conduct the necessary measures to improve air quality.

One of the easiest ways to do this is by improving the ventilation within your home. Open the windows or use exhaust fans to promote air circulation. Having good ventilation can also reduce the spread of infectious diseases and mold growth.

You can also achieve better indoor air quality by removing sources of pollution. These include tobacco smoke, radon, and pesticides. Switch to green cleaning products and practices to minimize harsh chemical use.

Plus, it is best to clean your HVAC systems regularly. Keep the air filters free from debris and dust to ensure proper working conditions. 

You can even consider investing in air purifiers and other air-cleaning devices. These help eliminate air pollutants inside your home.

Finally, carefully analyze and understand IAQ results. Doing so enables you to know what steps to take for air quality improvement. 


Many individuals know the harmful effects of outdoor pollution. However, most people are unaware that indoor air pollutants can be just as dangerous as outside factors.

You will need to measure indoor air quality to ensure good health and comfort in the long run. Use various devices, such as VOC and carbon dioxide sensors, to analyze pollutant levels. After getting the results, you can take the necessary steps to improve IAQ in your homes.

Do you have more questions about air quality? Feel free to reach out, and be sure to check out our indoor air quality guide with lots of tips and device recommendations.