Main indoor air pollutants

Indoor air chemical pollutants

Very volatile organic compounds

Very volatile organic compounds (VVOCs)

Volatile organic compounds

Volatile organic compounds (VOCs) are a large group of chemicals that easily become gases or vapors at room temperature. They are found in many common household products and building materials, and they can have a significant impact on indoor air quality (IAQ).

Semi-volatile organic compounds

Semi-volatile organic compounds (SVOCs)

Indoor air particles

Particulate matter (PM) is a mixture of solid particles and liquid droplets suspended in the air. These particles vary in size, composition, and origin, and their effects on human health depend on these characteristics.

PM is classified by its aerodynamic diameter, which is the size of a unit-density sphere with the same aerodynamic properties as the particle.

Coarse particles (PM₁₀)

Coarse particles are inhalable particles, with diameters that are generally 10 micrometers and smaller.

Fine particles (PM_2.5)

Fine particles are inhalable particles, with diameters that are generally 2.5 micrometers and smaller. Due to their small size, they can penetrate deep into the respiratory tract, reaching the lungs.

Ultrafine particles (PM_0.1 )

Ultrafine particles (UFP) are a subset of particulate matter with a diameter of less than 0.1 micrometers. Due to their extremely small size, UFP can penetrate deep into the lungs and potentially enter the bloodstream, raising concerns about their health effects.

Sources of indoor air pollutants

Indoor air pollutants can originate from various sources, both inside and outside the building. These pollutants can be either anthropogenic (caused by human activities) or natural.

Combustion sources

Combustion processes, such as those from gas stoves, fireplaces, and smoking, release various pollutants into the air:

• Carbon Monoxide (CO)
• Nitrogen Dioxide (NO2)
• Particulate Matter (PM_2.5 and PM₁₀)
• Volatile Organic Compounds (VOCs)

Building Materials and Furnishings

Many building materials and furnishings can emit VOCs, including:

• Paints and varnishes: These often contain solvents that release VOCs as they dry.
• Adhesives and sealants: Used in construction and renovations, these can emit VOCs for extended periods.
• Carpets and flooring: Some carpets and flooring materials can release VOCs, especially when new.
• Furniture: Certain types of furniture, particularly those made with pressed wood products, can emit formaldehyde, a type of VOC.

Household Products

A wide range of household products can contribute to indoor air pollution:

• Cleaning products
• Personal care products
• Pesticides and insecticides

Biological Sources

Biological pollutants are living organisms or substances derived from them that can cause health problems:

• Mold: Mold spores can trigger allergies and respiratory problems. Mold growth is often associated with dampness and poor ventilation.
• Bacteria and Viruses: These can cause infections and illnesses.
• Dust Mites: Microscopic creatures that feed on dead skin cells and can trigger allergies and asthma.
• Pet Dander: Tiny flakes of skin shed by pets that can cause allergies.

Indoor activities

• Cooking: Cooking activities can release PM, VOCs, and other pollutants into the air.
• Personal Activities: Smoking, using hobby materials, and even breathing can contribute to indoor air pollution.

Outdoor environment

• Radon: A naturally occurring radioactive gas that can seep into buildings from the ground and is a leading cause of lung cancer.

Concentration limit values for main air pollutants

	Pollutant	Averaging period	Concentration limit value		Reference
Organic air pollutants	Benzene	-	no safe level		WHO 2010
	Naphthalene	annual	10	μg/m3	WHO 2010
	Polycyclic aromatic hydrocarbons		no safe level		WHO 2010
	Tetrachloroethylene	annual	250	μg/m3	WHO 2010
	Trichloroethylene				WHO 2010
	Formaldehyde	30-minute	100	μg/m3	WHO 2010
Particulate matter	PM2.5	24-hour annual	15 5	μg/m3	WHO 2021
	PM10	24-hour annual	45 15	μg/m3	WHO 2021
	O3	8-hour peak season	100 60	μg/m3	WHO 2021
	SO2	10-minute 24-hour	500 40	μg/m3	WHO 2021
Inorganic gaseous pollutants	NO2	1-hour 24-hour annual	200 25 10	μg/m3	WHO 2021
	CO	15-minute 1-hour 8-hour 24-hour	100 35 10 4	mg/m3	WHO 2021
	Radon