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The Five AirScore Fundamentals and Why They Matter

Our three-week environmental survey gathers information about your building’s Indoor Air Quality. Whilst this is on-going, outdoor data from local and UK-wide in situ monitoring stations is also analysed and taken into consideration.

Once IAQ data is collected, our in-house environmental scientists test these data sets against the AirRated Scoring System, to generate an AirScore. Each fundamental parameter must meet a mandatory minimum threshold requirement for 95% of survey hours, in order to pass and become Certified. Below is a breakdown of the five elements that make up an AirScore, and why they matter.


PM2.5 is defined as fine particulate matter with a diameter less than 2.5 µm. The main indoor sources of indoor PM2.5 are combustion, mechanical processes and biological particles such as bacteria and viruses. Outdoor sources, both anthropogenic and natural, also have an influence on indoor PM2.5 concentration.

Fine particles like these are harmful as they can penetrate into the lungs and bloodstream. Short term exposure can cause irritation of the airways, coughing and cardiovascular problems. Long term exposure can cause premature death from heart disease and lung disease including cancer.

There is no safe level of PM2.5, but the guideline set by the World Health Organisation (WHO) is 10ug/m3. For every 10ug/m3 increase in levels of PM2.5 above this guideline, life expectancy is seen to be lowered by one year. 


Carbon Dioxide is a naturally occurring, colourless, odourless gas that makes up 0.04% (400ppm) of air. Indoor CO2 sources are human and animal respiration and combustion. Occupied indoor concentrations of CO2 tend to be significantly higher than outdoor.

CO2 is not harmful to health unless levels reach >4.0% of air composition (40,000ppm). However, there is a clear association between elevated indoor CO2 levels and increases in Sick Building Syndrome (SBS) symptoms. Furthermore, elevated levels of CO2 can cause up to 11% reduction in productivity, 23% impairment in decision making and 299% reduction in information usage. 


Total Volatile Organic Compounds (TVOCs) is a collective term used to define a group of common VOCs. VOCs comprise a wide range of chemicals, which may be emitted over a period of weeks or years. Their main source is construction and furnishing products such as sealants, paints, wall and floor coverings, cleaning products and air fresheners.

Short-term exposure to elevated levels of VOCs causes adverse effects like eye and respiratory tract irritation, headaches, dizziness, visual disorders and memory impairment. There has also been an association between higher concentrations of VOCs in indoor air with allergies, asthma, and other respiratory health symptoms. 

Long-term health effects include prolonged eye, nose and throat irritation as well as liver, kidney and central nervous system damage and even cancer.


Room temperature is the range of air temperatures that most people prefer for indoor settings which feel comfortable when wearing typical indoor clothing. Indoor temperature is affected by many variables from occupant density to mechanical ventilation effectiveness.

Poor thermal comfort can contribute to SBS symptoms including headaches, itchy skin, dry or sore eyes, blocked or runny noses and rashes. Research indicates that performance of office work is maximised between 21°C and 22°C, and for every degree above 25°C productivity is seen to decline by 2%. 


Relative humidity is the concentration of water vapour present in the air, expressed as a percentage. Moisture in the air arises from respiration and activities such as cooking and washing. Humidity directly affects occupant health and comfort, and the presence of biological pollutants such as mould spores.

Humidity lower than 30% causes eyes and skin to become dry and irritated and can aggravate conditions such as asthma. It also increases the risk of developing common colds, flu and other infections.

High humidity, greater than 60%, can impact feelings of lethargy and exacerbate allergies and respiratory diseases. Increased levels can also affect the concentration of volatile organic compounds (VOCs).

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It is evident that monitoring the five AirScore parameters is fundamental in improving IAQ and as a result, occupant health. To find out how your building performs against our AirRated Scoring System, contact us today.