5 MIN READ

How to Check Indoor Air Quality: Six Easy Steps

Despite being the least visible of building systems, ventilation is often the most important. Ventilation impacts people, productivity, comfort, energy, building performance, and, most importantly, indoor air quality. It’s essential to know the indoor air quality (IAQ) in your facility for many reasons.Healthwise, air pollutants can cause irritation, dizziness, fatigue, and asthma symptoms in the short-term, and can lead to respiratory diseases, heart disease, and cancer in the long-term. Additionally, poor ventilation can cause temperature and pressure imbalances which lead to comfort and productivity issues. Finally, the lost conditioned air due to poor ventilation forces your HVAC systems to work harder, which raises your HVAC costs. In this blog, we’ll outline what to lookout for to ensure your IAQ is where it needs to be, provide reference points to give you benchmarks for your IAQ, and point out potential solutions that fit your facility needs.

What to Measure and Why

There are many factors that can affect your IAQ. For one, elevated CO2 levels are a telltale sign of your ventilation effectiveness. If you find persistent readings greater than 1,000 ppm, there may be insufficient fresh air in your facility. While this number itself doesn’t represent an immediate health hazard, it is an effective indication that there may be other contaminants lurking in your facility’s air. The real dangers come with particulates, often known as PM2.5 or PM10. PM10 refers to particulate matter with an aerodynamic diameter of 10 micrometers or smaller, while PM2.5 refers to particulate matter with an aerodynamic diameter of 2.5 micrometers or smaller. For reference, the average human hair is 70 micrometers, making it 7 times larger than PM10s and 30 times larger than PM2.5. These particulates are so dangerous due to their tiny size; they can be easily inhaled and can make their way into your bloodstream. The smaller the particulate, the more of a threat it can pose for your health, as they can travel deeper inside. Below is a table from the World Health Organization that outlines appropriate levels of contaminants for your facility.

Another thing to look out for is spiking levels of volatile organic compounds (VOCs). VOCs are emitted as gases from certain solids or liquids, such as paints and paint strippers, aerosol sprays, disinfectants, stored fuels, building materials, adhesives, pesticides, and more. In the short term, a spike of VOCs in your facility can lead to headaches and nausea, and in the long term your employees could experience permanent liver and kidney damage. There is no standard “limit” for how many VOCs are “too many”, so just be sure to track spikes relative to your building’s baseline and root out the cause of those spikes.

A major danger of having a poorly ventilated facility is the risk of increased carbon monoxide levels. CO can be incredibly dangerous if inhaled in large quantities, so ensuring your facility maintains a safe level is of the utmost importance. You should be safety checking for combustion using the EPA outdoor NAAQS limits as a conservative “not to exceed” estimated limit. The recommendation is to keep it at less than 9 ppms for 8 hours or 35 ppms for 1 hour of exposure.

Other issues stemming from poor ventilation not directly related to health are your relative humidity (RH) and your pressure relationships. Your target should be to keep your facility’s RH at 30-50% to deter mold from growing in your facility and pests living in your facility.

Tools and Sensors: What You'll Use to Check Air Quality

Now that you know what to look for, you’ll need a way to measure it. Here’s a list of tools and sensors to use to check your IAQ:

Handheld/Data-Logging CO2 Meters (NDIR): Non-dispersive infrared technology is the most widely used technology for gas detection, particularly for CO2. Use these for mobile walk-throughs and 7–14-day logging in priority zones.

PM Sensors/Monitors: These may also be referred to as air sensors, air quality sensors, low-cost air pollution monitors, air pollutant motors, air pollutant meters or detectors, or low-cost air sensors. The EPA’s Enhanced Air Sensor Guidebook provides guidance in device selection and application, siting, and general IAQ recommendations.

CO Detectors and Loggers: Confirm installed code-required CO alarms and supplement with logging during tests and compare to the NAAQS as a conservative screen.
Optional: Use an anenometer or balometer for airflow, a smoke pencil for flow direction, and a manometer for pressure.

Where to Place Sensors

Knowing what to measure and how to measure is only part of the equation; you must also know where to measure your IAQ within your facility for the most accurate results. It is important to place your sensors in places that avoid direct air supply, like doors, windows, and vents. This is because your monitors can produce false results by reading the blasted outdoor air right at the source, failing to gauge the actual IAQ within your entire facility. Your sensors should be placed in areas that reflect typical building occupancy (production lines, packaging areas, offices, breakrooms, and docks) to ensure that the most used areas are safe. There should be at least one monitor per critical zone and additional sensors can be added near suspected sources of poor ventilation. To start, you should log at least one, ideally two, full workweek(s) to capture different shifts, occupancy peaks, and weather variability and how that affects your IAQ. The EPA’s Air Sensor Guidebook provides additional tips and tricks for ideal measuring spots, and much more.

Step-By-Step: How to Check IAQ In Your Facility

1. Plan the Assessment

Map spaces, HVAC zones, exhaust/make-up air, and complaint hotspots.
Define parameters and success criteria aligned with ASHRAE 62.1 ventilation intent.

2. Screen with Walk-Through Reading

Take handheld CO2/PM/RH spot checks during typical occupancy hours.
Take note of any odors, visible dust, moisture, and relevant pressure cues you notice during walk-throughs.

3. Deploy Data Loggers

Place CO2, PM, TVOC, and RH/temp loggers in recommended spots.
Capture at least 7-14 days across shifts, occupancy peaks, and different weather conditions.

4. Compare to Targets

Flag any zones that exceed the targets or show regular spikes at certain times (for example, during the first break, after lunch, or near the docks).

5. Diagnose Likely Causes

High CO2 without sources could mean there is insufficient outdoor air.
High PM could be caused by processes, housekeeping, or infiltration. Check local capture/filtration.
High TVOC could be due to products, materials, and/or cleaners. Pursue source control first.

6. Fix, Verify, and Document

Implement ventilation, filtration, source control, housekeeping, and moisture fixes.
Re-measure after implementing solutions to confirm IAQ improvement.

Screening and Investigation Levels

Now that you have your data, you need to know what to do with it. Here are the numbers to look out for when analyzing different ventilation problems:

CO2: While high CO2 readings are not an immediate health threat, they are a great indication of poor ventilation. Good numbers range from 600-800 ppm average in occupied hours. You should be investigating frequent peaks or consistent readings greater than 1,000 ppm.

PM 2.5: Best practice goal is ≤15 µg/m^3. Investigations should occur when approaching or exceeding 35 µg/m^3 over a 24-hour period.

CO: Should be kept well below 9 ppm over an 8-hour period and 35 ppm over a 1-hour period. Investigate any sustained readings.

Relative Humidity: Avoid rising above 60%, as that is where great discomfort and the increased potential of mold growth begins.

TVOC: While there is no universal, single limit, keep as low and stable as possible, investigating spikes and reducing sources first. You should establish early what your facility’s baseline ppm is and compare spikes to that.