Introduction
A room may feel stuffy, produce irritation or seem uncomfortable after people have occupied it for several hours. Indoor air quality is a combination of ventilation, pollutant sources, temperature, humidity and building operation. These conditions can influence comfort and, in some circumstances, health.
For investigators, indoor air quality matters for two reasons: it is part of the environment being documented, and discomfort can distract participants or affect the quality of observations. Measurements must be interpreted carefully. A single carbon-dioxide reading, for example, is not a complete air-quality assessment.
Carbon dioxide as a ventilation indicator
People exhale carbon dioxide (CO₂), so indoor concentrations often rise when occupancy increases and outdoor-air ventilation is insufficient for the number of occupants. CO₂ is therefore commonly used as an indicator of ventilation relative to occupancy.
It is important not to confuse typical indoor CO₂ levels with acute CO₂ poisoning. A consumer monitor reading above outdoor background does not, by itself, establish toxic exposure or explain a particular symptom. Interpretation depends on concentration, duration, context and applicable guidance.
Volatile organic compounds
Volatile organic compounds (VOCs) are a broad group of chemicals that can enter indoor air from paints, adhesives, cleaning products, fuels, furnishings, fragrances and other sources. Different compounds have different properties and health effects. A generic “TVOC” reading is not a precise identification of individual chemicals and should not be treated as a direct measure of health risk.
If a chemical source is suspected, identify the product and seek appropriate professional assessment. Do not deliberately expose participants to fumes as an experiment.
Humidity, temperature and ventilation
Relative humidity affects thermal comfort and can influence condensation and mould growth. Very dry or very humid conditions may cause discomfort. Temperature, radiant heat, air movement and clothing also shape how people perceive a room.
Ventilation can dilute indoor pollutants, but airflow may also carry outdoor dust, vehicle emissions or other contaminants indoors. A window being open does not guarantee adequate or clean ventilation.
Other indoor environmental factors
- Particulate matter from cooking, dust, smoke or outdoor pollution
- Carbon monoxide from faulty combustion appliances or generators
- Cleaning chemicals and fragrances
- Dampness and mould
- Poorly maintained HVAC systems
- Occupant density and activity
Carbon monoxide is a serious acute hazard and cannot be reliably detected by smell. Use properly installed, certified CO alarms and leave the area if an alarm sounds or exposure is suspected. Do not rely on a general-purpose air-quality sensor as a substitute.
AERM field protocol
Equipment
- Calibrated or quality-checked CO₂ monitor
- Temperature and relative-humidity logger
- PM2.5 monitor where particulate matter is relevant
- VOC monitor only with clear understanding of its sensor limitations
- Certified carbon-monoxide alarm for safety
- Site plan and field log
Procedure
- Record room volume, occupancy, activity and ventilation state.
- Place sensors away from direct breath, windows, doors and local pollutant sources unless those locations are specifically being studied.
- Allow sensors to stabilise according to manufacturer guidance.
- Log readings over time rather than relying on a single snapshot.
- Record doors, windows, fans and HVAC operation.
- Compare measurements with relevant national or recognised indoor-air guidance.
- If a dangerous condition is suspected, stop the session and seek professional help.
Interpretation and limits
Low-cost sensors can drift, respond to interfering compounds or use indirect estimation methods. A CO₂ monitor does not measure every pollutant. A TVOC sensor does not identify a specific chemical. A temperature or humidity reading does not diagnose illness.
Avoid attributing a witness's experience to a pollutant without appropriate evidence. Record the observation, the measurement and the uncertainty separately.
Conclusion
Indoor air quality is a measurable part of the investigation environment. CO₂ can help assess ventilation relative to occupancy; VOCs, particles, humidity and temperature add further context. Safety takes priority: suspected carbon monoxide or hazardous chemical exposure requires immediate action, not continued data collection. Properly documented air-quality measurements improve the reliability and welfare of field research.
AERM Core Principle: No anomaly is considered paranormal until environmental, psychological, technical, and scientific explanations have been systematically evaluated.
References and further reading
- World Health Organization. WHO Guidelines for Indoor Air Quality: Selected Pollutants.
- ASHRAE Standard 62.1. Ventilation and Acceptable Indoor Air Quality.
- US Environmental Protection Agency, indoor air quality and VOC guidance.
- Persily, A. and de Jonge, L. “Carbon dioxide generation rates for building occupants.” Indoor Air.
- NIOSH, guidance on carbon monoxide and workplace exposure.
- Central Pollution Control Board (India), ambient air quality resources and relevant guidance.
About AERM
AERM treats indoor environmental conditions as part of the evidence record. Its field practice prioritises participant safety, calibrated measurements and cautious interpretation.
Educational and safety disclaimer
This article is not a medical diagnosis or a substitute for an indoor environmental assessment. If a CO alarm activates, leave immediately and contact emergency or qualified services. Do not re-enter until the source has been assessed and the area declared safe.