Indoor Air Quality Monitoring Techniques: From Sampling Protocols to Data Analysis

Indoor Air Quality Monitoring Techniques: From Sampling Protocols to Data Analysis

Indoor air quality monitoring, through effective sampling protocols and data analysis, is crucial for identifying and mitigating hazardous pollutants in the workplace.

The World Health Organization (WHO) warns that air pollution is of great concern and impacts health in many ways. To better the situation, it’s necessary to focus on air quality. However, when thinking of air quality, the first thing that comes to mind is often the ambient (outdoor) environment.

What about the indoors? Although many people do not realize it, inside buildings can expose them to hazardous pollutants as well. As such, indoor work environments require attention. Let's start by better understanding indoor air quality (IAQ) and how it can be monitored. 

The Indoor Air Quality Problem

Humans spend 90 percent of their time indoors, according to the U.S. Environmental Protection Agency (EPA). Although buildings provide protection and shelter, they also have their downsides.

For instance, WHO stated household air pollution resulted in 3.2 million deaths annually in 2020. These deaths may be a result of exposure to hazardous pollutants such as:

  • Volatile organic compounds (VOCs) from paints and cleaning supplies
  • Particulate matter from dust and combustion sources
  • Biological contaminants like mold and bacteria

Exposure to these chemicals may result in health issues such as stroke, heart disease and lung cancer. It may also lead to acute and chronic respiratory diseases like asthma.

Notably, indoor environments go beyond residential buildings. Commercial, industrial and institutional buildings may also experience IAQ problems and related health issues.

For example, poor IAQ is linked to sick building syndrome (SBS). SBS occurs when time spent inside is related to acute health and comfort effects. For example, a study found that 40 percent of occupants experienced fatigue frequently. They also often had headaches, general muscle pain and burning in the eyes. Another study concluded that there are factors that increase the risk of developing SBS. 

Guide on IAQ Sampling and Analysis

Here is a guide on IAQ monitoring — from sampling to analysis.


Start with a thorough pre-sampling inspection before each sampling event. This first phase aims to identify conditions that may interfere with IAQ testing.

Evaluate the building's structure, floor layout, physical conditions and airflows. Use an IAQ questionnaire and building characteristics form to guide this process. Additionally, a product inventory must be conducted to identify potential sources of chemical interference.

Ensure that each room is inspected, and throughout the inspection, document all the details to ensure reliable results.


Control potential sources of volatile chemicals to minimize interference during sampling. Also, prepare the building by checking these:

  • Chemicals. Remove or seal containers of such chemicals and, if necessary, test them for leaks using a photoionization detector (PID).
  • Ventilation. Ensure proper ventilation at least 24 hours before sampling by using the building's HVAC system or opening windows and doors.
  • Operations. Maintain normal operating conditions for the HVAC system during sampling to replicate typical indoor environments.
  • Other activities. Avoid activities that could introduce volatile chemicals into the air within 24 hours before sampling.


Collect air samples from strategic locations to understand potential sources of pollutants and assess occupant exposure. For private residences, sample the basement, first floor and outdoor air. In schools and office buildings, take samples during occupied periods to capture typical exposure levels.

Position sample collection intakes at breathing zone height, about three feet above the floor. Remember that samples should be collected for at least one hour for accuracy and reliability. Avoid actions that could cause sample interference, such as using permanent markers or fueling vehicles.

There are various sampling methods for IAQ monitoring, including active and passive sampling:

  • Active. Active sampling uses a pump to draw air through a collection device, providing more precise and immediate results.
  • Passive. Passive sampling relies on diffusion and does not need a pump, making it suitable for long-term monitoring.

Choose the appropriate method based on the specific pollutants being monitored and the required sensitivity of the analysis.

In addition, gather high-quality data through quality control benchmarks. Follow these quality assurance measures during sample collection and laboratory analysis. Some examples include:

  • Using certified-clean sampling apparatus.
  • Adhering to sample holding times.
  • Maintaining proper temperatures and pressures.

Document all sampling details, including sample locations, chemical storage areas and HVAC conditions.


Once the samples are collected, analyze the data to interpret IAQ levels. Standard metrics include the air quality index (AQI) and threshold limit values (TLVs):

Analyze the data to identify potential issues or trends, such as recurring high levels of a specific contaminant.

Afterward, interpret the results. Interpretation involves comparing measured concentrations against regulatory standards and guidelines. Identify any exceedances and investigate potential sources and mitigation strategies.


IAQ monitoring is essential for maintaining a healthy and productive environment. Air quality monitoring techniques can help us achieve this goal. By implementing robust sampling protocols and performing thorough data analysis, it’s possible to identify and address potential air quality issues. This proactive approach will ensure indoor spaces remain safe and conducive to well-being.

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