What Is Indoor Air Quality (IAQ)? Definition, Standards, Pollutants, and How to Improve It
What Is Indoor Air Quality (IAQ)?
Indoor Air Quality (IAQ) refers to the quality of air inside buildings and enclosed spaces, especially as it relates to the health, comfort, and well-being of occupants. IAQ is influenced by indoor pollutants, ventilation rates, humidity, temperature, and building materials.
We spend most of our time indoors, whether in our homes, offices, shopping malls, restaurants, or other public environments. Real-time monitoring of indoor pollution factors is an important means of ensuring people's health.
Why Is Indoor Air Quality Important?
Indoor air quality is so important because it affects people's health. This is also why people are most concerned about it.
Specific symptoms depend on the duration of exposure to the contaminated environment. Short-term exposure may cause headaches, eye, nose, and throat irritation, fatigue, and difficulty concentrating.
Prolonged exposure can cause serious harm, potentially leading to asthma, chloronic respiratory disease, cardiovascular problems, and an increased risk of cancer. It is important to note that highly sensitive individuals and vulnerable groups, such as the elderly and children, are more likely to be affected and require special attention.
Productivity and Cognitive Performance
Research shows that good indoor air quality (IAQ) significantly improves productivity and cognitive function. Of particular concern is CO2 concentration; prolonged exposure to high CO2 levels can decrease concentration and negatively impact work and study efficiency.
In recent years, we have received numerous inquiries from schools and corporations seeking to improve student and employee productivity by creating a high-quality indoor air environment. Since 2020, several countries, including Germany, France, the UK, and the US, have enacted laws requiring the installation of CO2 air quality monitors in classrooms to ensure proper ventilation.
Energy Efficiency and Building Compliance
Modern energy-efficient buildings are often tightly sealed to reduce energy consumption. However, insufficient ventilation in airtight buildings can allow pollutants to accumulate.
Proper ventilation design helps balance energy savings with occupant health and ensures compliance with green building certifications such as LEED and WELL. For more details, please check our blogs：Best Air Quality Monitor for LEED v4.1 and WELL v2 Compliance (2026 Guide)
What Affects Indoor Air Quality?
Indoor air quality is influenced by multiple environmental and human factors.
1. Particulate Matter (PM1.0 / PM2.5 / PM10)
Particulate matter consists of tiny solid or liquid particles suspended in the air.
PM2.5 (particles ≤ 2.5 micrometers in diameter) can penetrate deep into the lungs and even enter the bloodstream. It is considered one of the most harmful air pollutants.
Real-time monitoring with an air quality monitor helps track PM2.5 concentration levels effectively.
2. Carbon Dioxide (CO₂)
CO₂ is primarily produced by human respiration indoors.
Above 1,000 ppm: may cause drowsiness and reduced concentration
Above 2,000 ppm: may trigger headaches and discomfort
A CO₂ monitor is an effective tool for evaluating ventilation performance.
3. Volatile Organic Compounds (VOCs)
VOCs are emitted from:Paint,Cleaning agents,New furniture,Adhesives, Renovation materials
Chemicals such as benzene and formaldehyde may pose long-term health risks. Total Volatile Organic Compounds (TVOC) is commonly used as a combined measurement indicator.
4. Carbon Monoxide (CO)
Carbon monoxide is a colorless, odorless, and potentially fatal gas produced by incomplete combustion.Common sources include:Gas stoves,Heating systems,Vehicle exhaust infiltration
High CO levels can become life-threatening within minutes, making CO alarms essential.
5. Humidity and Temperature
Humidity and temperature directly affect comfort and microbial growth.
Relative humidity above 60% promotes mold and dust mites
Below 30% may cause respiratory irritation
Extreme temperatures reduce comfort and productivity
6. Ventilation Rate
Insufficient ventilation increases the concentration of all indoor pollutants.
Industry guidelines recommend maintaining adequate fresh air supply per occupant to ensure acceptable indoor air quality.
What Is Considered Good Indoor Air Quality?
The following ranges are widely recognized as indicators of good indoor air quality. Based on years of customer service experience and relevant information from the WHO, we have compiled pollution level standards for various pollutants. Please see the following chart:
How Is Indoor Air Quality Measured?
Indoor air quality can be measured through several methods.
Air Sampling-Professinal
Professionals collect air samples using specialized pumps and send them to laboratories for analysis. This method can yield the most accurate results, but it requires more time and specialized equipment, especially the latter, which comes at a significant financial cost. It's difficult for ordinary families to afford.
Continuous Monitoring
Indoor air quality monitors provide real-time measurements of PM2.5, CO₂, VOCs, humidity, and temperature. These systems often generate historical trend charts and compliance-ready reports.
Continuous monitoring allows early detection of abnormal conditions and supports proactive IAQ management.
To make more cost-effective products available to ordinary households and businesses, CAREFOR has been dedicated to the development and production of air quality detectors for 10 years. We have researched and upgraded multiple models, offering desktop units suitable for real-time home monitoring and handheld detectors for commercial clients. These devices provide real-time monitoring, generate data reports, and offer an app for remote monitoring and integration with fresh air systems, meeting diverse customer needs.
IAQ Sensor Networks
Fixed sensor networks are ideal for large buildings. They can integrate with ventilation systems to automatically adjust airflow based on pollutant levels.These types of products require extensive technical support and special customization. They are suitable for large enterprises or companies with professional maintenance personnel.
Data Logging and Reporting
High-quality monitoring devices support data export for long-term analysis, compliance documentation, and performance verification.
Real-time tracking combined with historical data analysis is one of the most effective strategies for maintaining healthy indoor environments. Considering the needs of these customers, CAREFOR air quality monitors generally have this function.
Indoor Air Quality Standards and Guidelines
Several authoritative organizations provide IAQ recommendations and regulatory limits:
ASHRAE Standard 62.1 – Ventilation for Acceptable Indoor Air Quality
World Health Organization Air Quality Guidelines
Occupational Safety and Health Administration Workplace exposure limits
U.S. Green Building Council LEED v4.1 certification
International WELL Building Institute WELL v2 building standard
These standards provide reference limits for pollutants and ventilation requirements to protect occupant health.
How to Improve Indoor Air Quality，please check our blog：From Ventilation to Data Monitoring: 5 Practical Ways to Improve Indoor Air Quality
Frequently Asked Questions (FAQ)
Q1: What is the ideal indoor air quality level?
Ideal indoor air quality typically meets the following thresholds:
PM2.5 < 12 µg/m³, CO₂ < 800 ppm, TVOC < 0.5 mg/m³, humidity 40–60%, and temperature 20–26°C.
Q2: How can I test indoor air quality at home?
You can use a portable indoor air quality monitor to measure key parameters such as PM2.5, CO₂, and VOCs in real time. Professional laboratory testing is also available for detailed analysis.
Q3: What causes poor indoor air quality?
Common causes include inadequate ventilation, outdoor pollution infiltration, VOC emissions from materials, excess moisture and mold growth, cleaning chemical residues, and combustion appliance leaks.
Q4: Is high indoor CO₂ dangerous?
CO₂ at moderate levels is not toxic, but high concentrations (above 2,000 ppm) indicate poor ventilation and may cause headaches, fatigue, and reduced cognitive function. Extremely high levels (above 5,000 ppm) may pose direct health risks.
Q5: How often should indoor air quality be monitored?
Continuous monitoring is recommended for optimal control. At minimum, testing should be conducted after renovations, seasonal changes, or when occupants experience discomfort symptoms.
For more information, please see Indoor Air Quality Hub, IAQ Basics, CO2 Monitoring, LEED & WELL. For product pricing or customization inquiries, please contact us.