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What is it?
Particulate Matter 2.5 is fine particulate matter with a diameter less than 2.5μm. Some common examples are dust, sea salt, ash and vehicle exhaust.

Where does it come from?
Indoors, PM2.5 can come from a number of sources, such as combustion (e.g. heating and cooking), mechanical processes and biological particles (e.g. bacteria and viruses). Simply opening a window isn’t always the best solution for poor IAQ as indoor PM2.5 concentration can also be heavily influenced by both manmade and natural sources from outdoors.

Why is it a problem?
These fine particles can easily penetrate into the lungs and bloodstream, causing irritation of both upper and lower airways, as well as cardiovascular issues: this can even reduce life expectancy.

Although the World Health Organisation (WHO) has set a guideline of 10μg/m3, there is said to be no safe level of PM2.5.

What is it?
Carbon Dioxide (CO2) is a naturally occurring, colourless, odourless gas that makes up 0.04% (400ppm) of the air we breathe.

Where does it come from?
Human and animal respiration and combustion are the main sources of indoor CO2. Occupied indoor concentrations of CO2 are significantly higher than those outdoors.

Why is it a problem?
Studies have shown that elevated levels of CO2 can significantly impair cognitive function and cause up to 11% reduction in productivity. And even though it’s naturally part of the air we breathe, even very low levels of CO2 have been shown to cause adverse health effects, such as aggravating respiratory problems. There is also a recognised connection between elevated indoor CO2 levels and increases in Sick Building Syndrome (SBS) symptoms.

What are they?
Volatile Organic Compounds (VOCs) are compounds that can become gases or vapours: common examples in our daily lives are acetone, benzene and formaldehyde. TVOCs is a collective term which defines a group of common VOCs

Where does it come from?
VOCs comprise a wide range of chemicals, which may be emitted over periods of weeks or even years from construction and furnishing products such as sealants, paints, cleaning products, and air-cooling refrigerants for building services.

Why is it a problem?
In the short-term, exposure to elevated levels of VOCs can cause adverse health effects such as eye and airway irritation, headaches, dizziness, visual disorders and memory impairment. Long-term they can be even more dangerous, potentially causing damage to the central nervous system and even cancer. There is also an association between higher concentrations of VOCs in indoor air with allergies, asthma, and poor respiratory health.

What is it?
Room temperature describes the range of air temperatures that most people prefer for indoor settings that feel comfortable when wearing typical indoor clothing.

Where does it come from?
Indoor temperature is affected by many variables from occupant density to mechanical ventilation effectiveness and room temperature set point.

Why is it a problem?
Poor thermal comfort can contribute to Sick Building Syndrome (SBS) symptoms, which include headaches, itchy skin, dry or sore eyes, blocked or runny noses and rashes. Research also indicates that performance of office work is maximised at 21°C to 22°C and for every degree above 25°C productivity is seen to decline by 2%: the same drop has been seen for every degree below 19°C.

What is it?
Relative humidity is the concentration of water vapour present in the air. It’s expressed as a percentage.

Where does it come from?
Respiration and activities such as cooking and washing increase indoor humidity.

Why is it a problem?
Both high and low humidity can directly affect occupant health and comfort, and the presence of biological pollutants such as mould spores. Incidence of absenteeism due to respiratory infections was found to be higher among people working or living in environments with low or high relative humidities.