Indoor air quality monitoring – why it matters.

What is indoor air quality?

Indoor air quality (IAQ) broadly refers to the environmental characteristics inside buildings that may affect human health, comfort, or work performance. We monitor IAQ because we spend approximately 90% of our time breathing “indoor air”. Unlike outdoor air, indoor air is recycled continuously causing it to trap and build up pollutants. IAQ characteristics include the concentrations of pollutants in indoor air, as well as air temperature and humidity.

Why does indoor air quality matter?

Poor IAQ contributes to both short and long term health issues which can lead to decreased productivity, absenteeism, and possible litigation. Typical symptoms associated with poor indoor air quality include eye, nose, and throat irritation, headache, nausea, dizziness, and fatigue. In some cases exposure to indoor air pollution can lead to acute and chronic respiratory illnesses including asthma, lung cancer, pneumonia, systemic hypertension, chronic obstructive pulmonary disease (COPD), Legionnaires’ disease, and humidifier fever. See below for a table of major sources and potential health effects of indoor air pollution.

In some countries indoor air quality can be worse than outdoor air quality, especially when we consider the amount of time people spend indoors versus outdoors.

Factors contributing to poor indoor air quality

Gas and respirable particulates in the air are the primary sources that contribute to poor IAQ. Sources can include inadequate ventilation, poorly maintained HVAC systems, wood and coal stoves, non-vented gas heaters, environmental tobacco smoke, vehicle exhaust emissions, building materials, carpeting, furniture, maintenance products, solvents, cleaning supplies etc. The actual concentrations of these pollutants can also be amplified by other external factors including poor ventilation, humidity, and temperature.

Typical applications for IAQ monitoring

  • IAQ complaint investigation and analysis
  • HVAC system performance monitoring
  • Air quality engineering analysis
  • Mould investigation and remediation
  • Health and comfort assessment
  • Airport lounges, shopping malls, offices
  • Schools and kindergartens
  • Hospitals and elderly care facilities

Major Indoor Air Pollutants

Major Sources and Potential Health Effects of Indoor Air Pollutants
Sensor Pollutant Major Sources Potential Health Effects*
CO2 Carbon Dioxide Sick Building Syndrome (SBS), Excessive Building Occupancy and Inadequate Ventilation Fatigue; Eye, Nose and Throat Irritation; Headaches; Chest Discomfort; Respiratory Tract Symptoms
CO Carbon Monoxide Non-vented or Malfunctioning
Gas Appliances, Wood and Coal Stoves, Tobacco Smoke and Vehicle Exhaust Emissions
Headache, Nausea, Angina, Impaired Vision and Mental Functioning, Fatal at High Concentrations
COPM Environmental
Tobacco Smoke
Cigarettes, Cigars and Pipes Respiratory Irritation, Bronchitis and Pneumonia in Children; Emphysema, Lung Cancer and Heart Disease
VOC Organic Chemicals Aerosol Sprays, Solvents, Glues,
Cleaning Agents, Pesticides, Paints, Moth Repellents, Air Fresheners, Dry cleaned Clothing and Treated Water
Eye, Nose and Throat Irritation;
Headaches; Loss of Coordination; Damage to Liver, Kidney and Brain; Various Types of Cancer
O3 Ozone Ground Level Ozone Entering Indoors; Malfunctioning Air Treatment Systems; and Office Photocopiers and Printers Eye, Nose and Throat Irritation; Coughing; Chest Discomfort; Reduced Lung Function; Shortness of Breath
NO2 Nitrogen Oxides Non-vented or Malfunctioning
Gas Appliances and Vehicle Exhaust Emissions
Eye, Nose and Throat Irritation; Increased Respiratory Infections in Children
PM TSP (total suspended particulates)PM10 (thoracic fraction ≤10 μm)PM2.5 (respirable fraction ≤2.5 μm)PM1 (particles ≤1.0 μm) Cigarettes, Wood and Coal Stoves, Fireplaces, Aerosol Sprays and House Dust Eye, Nose and Throat Irritation;
Increased Susceptibility to
Respiratory Infections and
Bronchitis; Lung Cancer
CHCO Formaldehyde Pressed Wood Products e.g.
plywood and MDF; Furnishings; Wallpaper; Durable Press Fabrics
Eye, Nose and Throat Irritation; Headache; Allergic Reactions; Cancer
Other Sources and Potential Health Effects of Indoor Air Pollutants
Biological Agents
(Bacteria, Viruses, Fungi, Animal Dander, Dust Mites)
House Dust; Pets; Bedding; Poorly Maintained Air Conditioners, Humidifiers and Dehumidifiers; Wet or Moist Structures; Furnishings Allergic Reactions; Asthma;
Eye, Nose and Throat Irritation;
Humidifier Fever, Influenza
and Other Infectious Diseases
Asbestos Damaged or Deteriorating Insulation, Fireproofing and Acoustical Materials Asbestosis, Lung Cancer,
Mesothelioma and Other Cancers
Lead Sanding or Open-Flame Burning
of Lead Paint; House Dust
Nerve and Brain Damage,
Particularly in Children; Anemia;
Kidney Damage; Growth Retardation
Radon Soil Under Buildings,
Some Earth-Derived Construction
Materials and Groundwater
Lung Cancer

Indoor air quality standards

As a result of increased awareness of the health risks of poor air indoors, governments are tightening up standards and enforcing monitoring on building owners. Initially the standards apply to public places and office buildings. In the future it is feasible that standards could apply to newly built residential buildings.

The trend towards tighter regulation is particularly evident in Asia where people spend a large amount of time indoors in air conditioned environments. In recent years Singapore, Taiwan and Hong Kong have all taken steps to better protect human health indoors.

Methods for assessing IAQ

There are two main methods for assessing the quality of indoor air:

  • Real-time (continuous) measurements. Real-time monitors can be used for detection of pollutant sources and provide information on the variation of pollutant levels throughout the day. Aeroqual is one such manufacturer of equipment for real-time IAQ monitoring.
  • Integrated sampling with subsequent laboratory analysis. Integrated samples, normally obtained during the 8 working-hours for offices, can provide information on the total exposure level of a particular pollutant.

Regardless of the choice of the method, it is very important to ensure proper operating of the equipment and handling of the samples, as well as strict quality assurance procedures including equipment calibrations and operation in accordance with the manufacturer’s instructions.

Find out more about the Aeroqual range of indoor air quality monitors here