Indoor Air Quality Monitoring Methods - A Definitive Guide

The definitive guide to indoor air quality monitoring methods

Indoor Air Quality monitoring has long competed with outdoor or ambient air quality monitoring for attention. This is the case not only in public discourse and household behaviours but also in popular research.

The Covid-19 pandemic changed many things. People’s focus on indoor air quality (IAQ) is one of them. Since people spend most of their time in enclosed environments, the threat of disease transmission brought indoor air quality monitoring methods to the forefront of the air quality conversation.

Outdoor air quality monitoring focuses primarily on outdoor pollutants like particulate matter (PM). When it comes to indoor air quality monitoring systems, however, things are a little bit different.

For starters, the onus of ambient air quality management is on the public health authorities. On the other hand, households, building owners, and employers must take indoor air quality management into their own hands. This imperative is highlighted further by the absence of explicit indoor air quality standards in India, though some industry standards and guidelines exist. The pollutants to be monitored, sampling methods, and appropriate technologies also vary for indoor air quality management as opposed to outdoor air.

What is IAQ monitoring?

Indoor air quality monitoring methods are focused on gathering continuous data on the concentrations of gases, chemicals, and particles within indoor environments. They help building owners, managers, and occupants to identify problem areas, detect trends, and make necessary adjustments to improve indoor air quality. Such improvements can reduce the risk of airborne disease, prevent the growth of mould and other harmful organisms, and provide comfort to building occupants. The primary focus of improving IAQ is to safeguard the health and well-being of the building occupants.

Indoor air quality monitoring methods may yield an air quality index (AQI), which is an indicator of the overall health of your indoor air. It cumulates the concentration and effects of multiple common indoor air pollutants to give you a single number at any point in time. IAQ may also be expressed in terms of the concentrations of each individual pollutant, like PM2.5, PM10, carbon dioxide, ozone, or total volatile organic compounds (tVOCs). Temperature and humidity data that pertain to thermal comfort are also important aspects of indoor air quality monitoring systems.

The goals of IAQ monitoring

If you’re looking to set up an indoor air quality monitoring system, you probably have a particular objective in mind. 

Indoor air quality monitoring methods are typically employed to determine indoor air pollutant levels before and after a new clean air solution is installed—this helps users assess whether their intervention was useful.

They are also employed when there is a problem that needs fixing viz. building occupants experiencing Sick Building Syndrome, bad odour, or a feeling of stuffiness. Monitoring IAQ can help identify the source of such problems so that remedial measures can be employed. 

Indoor air quality monitoring systems are also installed to optimise building ventilation based on building occupancy and pollution-causing activities. This not only improves IAQ but can also help optimise energy costs.

The most proactive people in using indoor air quality monitoring methods for their homes or offices are the ones doing it right, because if you aren’t measuring, you are only guessing.

If you wait for a serious problem to emerge before you start taking an interest in your indoor air, you’re already too late.

Categorising indoor air quality monitoring methods

Every indoor air quality monitoring system uses a particular sampling method and tracks some specific parameters. We can categorise IAQ monitors based on these two factors.

Sampling method.
Spot testing involves a periodic assessment that provides a snapshot of your IAQ at any one point in time. It is usually implemented using expensive portable equipment and may require a professional to do it right.

On the other hand, continuous indoor air quality monitoring (also called real-time IAQ monitoring) involves deploying sensors on a permanent basis to collect air quality data continuously, 24×7. Such a sampling method gives you minute-by-minute air quality readings. The data you get when you use this technique can help you identify trends throughout the day, month, and year. It can also alert you to dramatic increases in the concentration of any pollutant.


Indoor air quality monitoring methods can also be classified based on which pollutant or environmental condition they are designed to track. Based on the sensors they are fitted with, they may measure a combination of particulate matter, carbon dioxide, carbon monoxide, ozone, VOCs, temperature, and/or humidity.

Indoor air quality monitoring methods

Before you can measure the quality of indoor air, you need to take care of three things: hardware (like strategically placed sensors, detectors, and monitors), software (to manage current and historical IAQ data), and services (to analyse that data and develop actionable solutions).


For monitoring in commercial spaces, deployment of good quality commercial grade monitors is required. The range of various pollutants and their accuracy should conform with the requisite building certification.

Installation and deployment:

Devices should typically be wall mounted in the vicinity of the occupants in the breathing zone. Breathing zone could mean a location on the wall that is at a minimum of 3 ft from the ground, but not exceeding 6-7 ft. The number of devices in a given space, will depend on the specification of the certifying agency. Typically, guidelines as defined in the WELL certification are a good indicator. Separate enclosed occupant rooms will require a separate monitor, but large office spaces with common seating areas could do with a single monitor.

Placement of monitors is best avoided in close proximity of exit doors & window openings.


Monitors must have the option of being connected over the Wi-Fi network or via the Building Management System. They should facilitate uploading of data to the cloud so as to be able to see the data on the manufacturer’s dashboard or on a dashboard created by the BMS vendor. This is an important tool to understand the trends of various pollutants as well as the health of the building.


Upkeep and calibration of all monitors is an important part of the selection of monitors. Sensors tend to drift over a period and hence require calibration (replacement) on a periodic basis to ensure reliability of the data. Calibration should be easy, convenient and involve minimum downtime.

Bridging the gap between IAQ monitoring and indoor air quality management

Collecting continuous, real-time data is one thing. Deriving value from it via actionable insights is another thing altogether. Transforming your indoor air quality monitoring system into an indoor air quality management system involves building a robust data set, analysing trends, and identifying problem areas. This is where you can begin to make proactive, long-term decisions that can help you not only remedy IAQ problems but also prevent them in the first place.

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