How to Test Air Quality

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Written By Jamila W.

Indoor air quality testing (IAQ) is a critical part of safeguarding the environmental safety of buildings and addressing poor air quality. IAQ assessments involve a range of methods that detect levels of common indoor air pollutants, with the data generated used to guide steps to mitigate their effects. In this article, we explain how to test indoor air quality, outlining the professional test methods and equipment used to assess and accurately measure pollutants in indoor air. 

Test Levels of Common Pollutants in Indoor Air

office building

IAQ testing determines levels of pollutants in indoor air in industrial, public, commercial, and residential buildings. These air contaminants span noxious gasses, particulates, chemical pollutants, and biological agents. Poor indoor air quality causes wide-ranging short and long-term health problems, including cancer. This makes the presence of indoor contaminants an important environmental health issue. 

Here are some of the main pollutants measured in indoor air quality testing:

  • Particulate Matter: These are solid and liquid particles released from a variety of organic and inorganic sources.When inhaled, PM1, PM2.5, and PM10 particles deeply penetrate the airways, causing long-term respiratory problems. Particulate Matter includes particles as small as 1 micrometer in diameter that are suspended in air.
  • radon: This odorless and colorless radioactive gas, released from underground rocks, enters and accumulates in poorly sealed buildings. Long-term exposure to radon gas raises the risk of developing lung cancer.
  • Nitrogen dioxide (NO2): This respiratory irritant is released during the combustion of natural gas and other fuels. NO2 is also associated with the development of dementia, diabetes, and other health problems.
  • Volatile Organic Compounds (VOCs):There are at least 10,000 VOCs which are gaseous chemicals present in a range of home renovation, interior decor, and cleaning materials. Health effects of VOCs include skin, eye, and respiratory irritation, with long-term exposure raising the risk of developing cancer.   
  • Ozone: This odorless, colorless gas is a known respiratory irritant. In properties, it can be generated by printers, photocopiers, and other electronic devices. Outdoor ozone levels also rise in hot weather, leading to increased concentrations in indoor air. 
  • Carbon Monoxide (CO): Inadequate fuel combustion and exhaust air removal from gas appliances like gas space heaters cause the release of this dangerous colorless gas. Dangerous levels of this poisonous gas cause carbon monoxide poisoning which can kill.

How to Test Indoor Air Quality

people looking at a bluerprint

Here is a step-by-step outline of how a professional test of commercial or home air quality is carried out. Professional IAQ assessment is usually undertaken for large buildings, new developments, or where an existing building will be significantly renovated. Another reason for completing a detailed assessment of air quality is to respond to complaints from building occupants or to improve their health and well-being. 

Step 1: Is Indoor Air Quality Testing Necessary?

The first step in testing indoor air quality is deciding if an IAQ assessment is even necessary. For indoor air pollutants to cause a problem, there must be:

  1. A source of the pollutant
  2. A pathway for the pollutant to travel within the building
  3. A receptor who is affected by the pollutant (may be human or non-human)

This is called the source-pathway-receptor model. Without a source, pathway, or receptor, indoor air quality testing is unlikely to be needed.

Outdoor air quality assessment is another baseline assessment that is used to determine if formal IAQ testing is required. British studies have demonstrated that buildings reduce the concentration of outdoor air pollution concentrations by between 20 and 70%. Outdoor readings are then used to infer the indoor air quality. 

Step 2: Undertake a Scoping Study

Detailed IAQ testing commences with a scoping study. This stage of indoor air quality testing gathers information about the indoor environment to be tested and assesses the following factors:

Factors assessed IAQ testing considerations
Building design A review of building plans and specifications, gathering information related to:Floorspace and room volumesThe building’s natural and mechanical ventilationAirflow through the building and the presence of any dead zones (where air does not circulate)HVAC specificationsThe level of sealing of the building 
Building useThe occupancy and use of the building including:The amount of time spent in various locations in the buildingThe presence of electronicsActivities like smoking/vapingThe density of occupancy (overcrowding)
Potential pollutant sourcesEvaluation of local outdoor pollutantsIdentification of potential indoor pollutant sources (e.g. gas stoves, insulation material)Consideration of timings or seasonality of pollutant release
The indoor environmentThe baseline temperature, humidity, and CO2 levels

Scoping enables IAQ testing technicians to identify potential pollutants and their sources. Problems like inadequate ventilation, toxic mold, or pet dander can be identified at this stage. The scoping study determines the level of IAQ testing that is necessary. In the case of new buildings, IAQ monitoring may be completed instead of testing absolute pollutant levels, using plans and information about building materials. Technicians can also provide recommendations for improving air quality if a formal IAQ assessment is not undertaken. 

Step 3: Test Air Quality

Indoor air quality testing varies in its breadth and level of detail. Where scoping stage information indicates that an IAQ assessment is necessary, the next stage is to decide if simple or more detailed testing is necessary.

Simple IAQ assessments

two men looking at a paper

Simple IAQ assessments assess the risk of exposure to particulate pollutants and identify the need for formal testing if the risk of dangerous levels of indoor air pollutants is medium or high. Technicians use information obtained in the scoping study to evaluate the occupation and activity in the building. Basic air quality assessments emphasize recommendations for eliminating common pollutant sources and improving IAQ rather than measurement of the absolute levels of pollutants.

Detailed IAQ Assessments

woman looking through wires

Many professional indoor air quality testing contracts only undertake a detailed assessment of air quality when indicated by scoping studies or a simple assessment. Detailed indoor air quality testing includes: 

  • Measurement of pollutant concentrations
  • Temperature measurement
  • Relative humidity measurement
  • Airflow readings
  • Computer modeling (especially if the building has not been completed)
  • Ongoing indoor air quality monitoring 

Considerations for detailed indoor air quality testing

Professional experience and judgment are used to gauge the exact nature of a detailed assessment. Accessibility, budget, and timeframes influence the testing approaches used. Testing is carefully planned to maximize data capture while ensuring that the equipment used is unobtrusive and building occupants are not disturbed. 

kitchen counter

Indoor air quality has high spatial and temporal variability. This can make individual readings meaningless. If the time and budget are available, contractors undertake IAQ monitoring over a prolonged period, to better characterize the level of pollutants in indoor air. If time and data acquisition are limited, indoor chemistry computer modeling can be used to give an indication of pollutant levels and the attendant risks to occupants. 

Detailed testing of indoor air quality also includes documentation of relevant factors that include:

  • The amount of time that has passed since a building was completed or refurbished.
  • The recent completion of  cleaning or decoration
  • The presence of ventilation, heating, or cooling in the building at the time of pollutant measurement.
  • Occupant activities like cooking, exercise, or smoking.
  • Outdoor air quality and other pollutants like vehicle traffic.

Step 4: Mitigation Strategies and Reporting 

Once air quality testing has been completed, technicians use the acquired indoor air quality data to devise strategies for reducing pollutant levels. Property owners or building managers are advised on how to improve indoor air quality and occupant comfort. Advice may include the installation of carbon monoxide detectors, the use of an air purifier, or retrofitting of HEPA filters in an air conditioner.

Proposed solutions for improving indoor air quality are based on the pollutants and sources that have been identified. Using all information available a comprehensive IAQ assessment report is compiled that outlines the scoping, testing methodologies, results, risk assessments, and professional recommendations for mitigation, improvement, and prevention of indoor air pollution.

How Indoor Air Quality Is Measured

Indoor air quality testing primarily targets common indoor air pollutants described above. It is rarely exhaustive, so technicians will use scoping, simple assessments, and their expertise to decide which pollutants should be measured. If a building is undergoing IAQ testing to comply with guidance or certifications, the pollutants specified by the regulator should be measured. 

Indoor Air Quality Testing Specialized Equipment

Air quality testing uses two types of devices for measuring pollutant levels:

  • Continuous monitoring devices including electrochemical sensors with SMART capabilities. These sensors are capable of recording pollutant levels and variation in detail, often transmitting data wirelessly in real-time. 
  • Passive devices including diffusion tubes and radon test kits are suitable for long-term installation at multiple locations in a building due to their low cost. However, they cannot capture temporal variations in pollutant concentrations. 
  • Ambient air quality monitoring equipment can also be used. It has relatively high sensitivity, detecting pollutants at micrograms per cubic meter (µg/m3) or parts per billion versus the milligrams per cubic meter (mg/m3) measurements used for workplace exposure measurements.

The precise monitoring equipment is determined by the pollutant, assessment protocols (including detection limits), and timescale for completion of monitoring. Here are some examples of monitoring equipment used:

Type of sampling equipmentExample(s)Pollutants detected
Passive sampling1. Badges
2. Diffusion tubes
3. Sorbent tubes
1. VOCs
2. Radon
3. Ozone Nitrogen dioxideSulfur dioxide
Pumped sampling 1. Filters
2. Sorbent tubes
3. Sample bags
4. Liquid and bubble samplers
1. Asbestos
2. Biologicals including mold, bacteria, and viruses
3. Metals
3. VOCs, inorganic glasses
Indicative sampling1. Electrochemical sensors (SMART sensors)
2. Colorimetric indicator sampling
1. VOCs, inorganic glasses
Real-time reference sampling1. Gas analyzers
2. Sensor-based optical particulate matter measurements
1. Particulates
2. Nitrogen and sulfur dioxide
3. VOCs
Sampling duration for measuring indoor air quality
Accurate indoor air quality testing requires a duration that is sufficient to provide a representative sample of pollutant concentrations. If sampling is taken over a prolonged period, it is possible to identify temporal changes in pollutant concentration and other variables.

Other factors that determine the duration of indoor air quality measurement include:
The reason for completing the survey (occupant complaints may necessitate extending sampling periods)
The pollutants that are being measured
The use of the building 
Short-term air quality measurements of air inside buildings are usually taken by a technician over 15 minutes. This type of IAQ testing may be necessary for sensitive environments like electronics manufacturing facilities, operating theaters, or locations where installed sensors could be tampered with. These measurements can also be used for activities like cleaning or cooking where an acute emission of pollutants may be expected.

Where to test indoor air quality

Locations for indoor air quality testing depend on whether the sampling technique relies on diffusion (passive) or is actively powered. The Environmental Protection Agency (EPA) provides detailed guidance that specifies the number and location of sampling points for air quality testing. The Environmental Protection Agency recommends:

  • Prioritizing testing in the most populated or well-used spaces in a building.
  • Placing indoor sensors at the typical breathing zone height of three to six feet.
  • Placement of sensors away from actual or potential sources of air pollution or air purifiers and cleaners which are air pollution sinks.
  • Ensuring that measuring equipment has free airflow around it.
  • Avoid placing sensors behind appliances or in corners or alcoves, due to limited air movement.
  • Avoid placing sensors in HVAC ducts, windows, doors, or other places where results could be unduly influenced by outside air. 
  • If SMART sensors are used, technicians should ensure that there is an adequate Wi-Fi or cellular connection for data transfer as part of the air quality tests.  Powered monitoring equipment may also require access to a mains outlet. 

Technicians may also use wearable devices that monitor air quality as they walk through a building that is being assessed. Personal sampling equipment is particularly useful if there is an occupant complaint or known indoor air quality problems, as the technician can move through the building as an occupant would.

In Conclusion 

Indoor air quality testing provides the data that building owners and managers need to ensure that indoor air is safe for occupants. Reliable IAQ testing is a multi-step procedure that uses varied techniques and equipment to gauge the level of indoor air pollution, its sources, and solutions for improving air quality. Hire a professional with the expertise necessary to undertake targeted identification of pollutants that cause indoor air quality problems, using appropriate methods.