The EDIAQI Decision Tree
EDIAQI Wiki / Decision Support and Tools / The EDIAQI Decision Tree
Start with: A specific concern or question.
Investigate: Measurements, room use, indoor activities, outdoor conditions, and building systems.
Decide: Which action addresses the likely cause.
Check: Whether the action improves conditions.
Jump to: Overview · Why Measure? · How to Measure? · What Is the Issue? · What Now? · Practical Examples · Technical Details · Related Pages · References
Concept and Purpose
The EDIAQI Decision Tree organizes this page around four practical questions: Why measure? How to measure? What is the issue? What now? Use these questions to plan an investigation and choose the next action.
For example, a classroom that feels stuffy calls for a different investigation from a home with particle peaks during cooking or a room with recurring dampness. Start by describing the concern, then select the measurements and observations that can help answer it.
EDIAQI's observation toolkit and monitoring guidelines describe measurement methods, sensor evaluation, and the design of monitoring activities.[1][2] Choose instruments that measure the pollutants or parameters relevant to your concern, and review their documented performance and limitations.[2]
The Four Stages of the EDIAQI Decision Tree
1. Why Measure?
Define the question and the decision that the results should support:
- Ventilation: Does air exchange appear adequate for the way the room is occupied?
- Indoor activities: Do cooking, cleaning, smoking, or other activities coincide with changes in pollutant levels?
- Outdoor influence: Do indoor readings change with outdoor air conditions?
- Building conditions: Are there signs of moisture problems, persistent material emissions, or poorly functioning ventilation?
- Verification: Did a change in ventilation, source control, or air cleaning improve the conditions being investigated?
Different pollutants have different health effects and require different assessment methods. WHO guidance covers selected indoor pollutants, dampness and mold, and pollutants such as PM2.5 and NO2.[3][4][5]
Decide which guideline or requirement is relevant before interpreting the results. Distinguish health-based guideline values from legally applicable requirements. Match comparisons to the pollutant, units, averaging period, and measurement method.[3][5]
2. How to Measure?
Select instruments for the question you are investigating. EDIAQI describes low-cost sensor evaluation alongside sampling and analytical methods for specific pollutants.[1]
| Measurement | What to Consider |
|---|---|
| Carbon dioxide (CO2) | Interpret CO2 with occupancy, outdoor background, and the ventilation conditions of the room. A single concentration is not a universal measure of overall IAQ.[6] |
| Particulate matter (PM2.5, PM10) | Review sensor performance for the particle types and environmental conditions expected in the room. Check measurements against suitable reference instruments when needed.[1][2] |
| VOCs and Formaldehyde | Confirm which compounds the device or sampling method measures. Use compound-specific sampling and analysis when a specific substance needs assessment. A TVOC reading alone does not establish compliance with a formaldehyde guideline.[1][3] |
| Temperature, Humidity, and Building Observations | Record temperature and humidity to help interpret sensor behavior. Investigate visible dampness and moisture sources through building inspection as well as measurements.[2][4] |
- Place the monitor for the target occupants. D3.2 gives 1–2 m as a general breathing-zone range for low-cost sensors, with adjustments for seated children and sleeping occupants. Follow pollutant-specific guidance and the instrument instructions.[2]
- Allow free airflow. For representative room measurements, avoid obstructed locations and the immediate influence of local sources, heaters, ventilation outlets, and air cleaner exhausts. Source-focused investigations may require a different location.[2]
- Choose a suitable duration. Match the campaign to the pollutant, method, room use, and relevant averaging period. Include representative occupied and unoccupied conditions where relevant, and distinguish sensor evaluation from assessment of conditions in an occupied room.[2]
- Keep an activity log. Record occupancy, window opening, ventilation operation, cooking, cleaning, and air cleaner use, together with sensor location and any changes during monitoring.[2]
- Check data quality. Review missing records, timestamps, instrument maintenance, calibration information, and sensitivity to temperature or humidity. Agreement between two monitors does not by itself establish accuracy against a reference.[1][2]
3. What Is the Issue?
First check that the readings are reliable and that any comparison uses the correct pollutant, units, and averaging period. Use low-cost sensor readings for an initial investigation, with suitable reference measurements when required by the assessment purpose.[2]
Compare indoor and outdoor measurements of the same pollutant over matching periods, using instruments with suitable performance. Record possible sources and relevant room conditions.[2]
- Outdoor contribution: Investigate whether indoor changes follow outdoor changes, allowing for transport delays and removal indoors.
- Indoor contribution: Investigate repeated associations with cooking, cleaning, combustion, room use, or material emissions.
- Building and system contribution: Inspect ventilation operation, moisture problems, and the condition of the building.
- Uncertain or mixed contribution: Improve the measurement comparison, extend observations, or obtain specialist measurements before assigning a single cause.
The indoor-to-outdoor ratio is a clue, not a binary source test. I/O > 1 can occur during transient conditions; I/O < 1 does not exclude indoor sources. See the model assumptions below.[7]
CO2 depends on occupancy, occupant generation rates, outdoor background, and ventilation. A value such as 1000 ppm should not be treated as a universal health or IAQ boundary for every room.[6]
4. What Now?
Choose an action that addresses the likely cause, then plan how to evaluate the result.
Reduce or remove avoidable pollutant sources. For activity-related peaks, investigate the activity and available source exhaust before relying on room air cleaning. Examples include avoiding indoor smoking, selecting low-emission materials, and using kitchen exhaust during cooking.[8]
Have persistent ventilation problems assessed. Account for both indoor emissions and outdoor air quality when choosing a ventilation strategy; increasing outdoor air supply can also introduce outdoor pollutants.[9] For dampness or mold, address the moisture source and the affected building materials; air cleaning does not resolve the moisture problem.[4]
Consider air cleaning and filtration alongside source control and ventilation. Assess particle filtration for particle concerns and pollutant-specific gas treatment for gaseous contaminants. Choose a technology appropriate to the pollutant and document how its performance will be checked.[8] Where outdoor pollution contributes to indoor exposure, consider filtration of incoming outdoor air as part of the ventilation strategy.[9]
Repeat relevant measurements under comparable room use and outdoor conditions. Keep a record of what changed, including ventilation settings and instrument location. Choose the follow-up duration for the question and method; a fixed seven-day test is not sufficient for every pollutant or assessment.[2] Compare the results with the applicable averaging period, and arrange further investigation if the evidence remains uncertain.[3][5]
Target Audience Practical Application Matrix
The examples below suggest ways to apply the four questions.
| Audience | Example Question and Next Step |
|---|---|
| Residents | Do particle peaks coincide with cooking? Record cooking and exhaust use, investigate source control, and compare the readings after a change. |
| Schools and Kindergartens | How does classroom CO2 change during lessons? Record attendance, timetable, and ventilation operation, then discuss the findings with the building manager. |
| Building Managers | Are concerns associated with room use, ventilation schedules, or moisture? Combine measurements with inspection and verify the effect of maintenance. |
| Municipalities | Which public buildings need further investigation? Use comparable monitoring plans and document uncertainty before prioritizing specialist assessments or improvements. |
Simplified model: one well-mixed room, constant conditions, no inter-room transport or particle transformations.[7]
dCin/dt = a P Cout + S/V − (a + k) Cin
Cin, Cout: concentrations (µg/m³); t: time (h); a: air exchange (h⁻¹); P: penetration factor; S: emissions (µg/h); V: volume (m³); k: other removal (h⁻¹), including deposition and filtration.
For S = 0, a > 0, 0 ≤ P ≤ 1, and k ≥ 0:
I/O = Cin/Cout = a P / (a + k) ≤ 1
Use only at steady state with nonzero outdoor concentration.
After emissions stop (S = 0):
Cin(t) = Cbg + [Cin(0) − Cbg] e−(a+k)t
Cbg = a P Cout / (a + k)
Decay describes total removal, a + k, not ventilation alone. Retain non-negligible background.[7]
Related Wiki Pages
References
- ↑ 1.0 1.1 1.2 1.3 1.4
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11
- ↑ 3.0 3.1 3.2 3.3 World Health Organization. (2010). WHO guidelines for indoor air quality: selected pollutants.
- ↑ 4.0 4.1 4.2 World Health Organization. (2009). WHO guidelines for indoor air quality: dampness and mould.
- ↑ 5.0 5.1 5.2 World Health Organization. (2021). WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide.
- ↑ 6.0 6.1 Persily, A. K., & Polidoro, B. (2022). Indoor Carbon Dioxide Metric Analysis Tool. NIST Technical Note 2213. National Institute of Standards and Technology.
- ↑ 7.0 7.1 7.2 Emmerich, S. J., & Nabinger, S. J. (2000). Measurement and Simulation of the IAQ Impact of Particle Air Cleaners in a Single-Zone Building. NISTIR 6461. National Institute of Standards and Technology.
- ↑ 8.0 8.1 EDIAQI. D3.3 Novel Indoor Air Quality Monitoring Solutions Handbook. (Public PDF not listed as available on the EDIAQI public deliverables page; checked October 9, 2026.)
- ↑ 9.0 9.1 Asikainen, A., Carrer, P., Kephalopoulos, S., de Oliveira Fernandes, E., Wargocki, P., & Hänninen, O. (2016). Reducing burden of disease from residential indoor air exposures in Europe (HEALTHVENT project). Environmental Health, 15(Suppl 1), S35.