Calculating an actionable indoor air quality index
An air quality index (AQI) is a descriptive scale used to show how polluted the air is. There is little research on the health effects of air pollution in short time frames. This is why air quality indexes are typically only provided for time periods of an hour or longer. This method is effective when it comes to measuring outdoor air quality. The story is different indoors, however – it is important to be notified as soon as possible when air quality deteriorates so that the users of the space can take direct and immediate action to remedy the situation. Concentrations of some air pollutants can be between 2 to 10 times higher indoors than outdoors.
To solve this issue, Breeze Technologies uses a real-time air quality index for indoor applications that looks at the average air quality from the last five minutes as if it had already been measured in the last full hour. We calculate our indoor air quality index (IAQI) based on several key indicators. The overall air quality index for indoors is thus based on the worst air quality index rating among them. Let’s take a closer look at how this is done.
Breeze Technologies‘ overall indoor air quality index (IAQI)
Our overall IAQI is determined according to the worst rating of the following three parameters: carbon dioxide (CO2), indoor climate (temperature and humidity), and volatile organic compounds (VOCs). For example, if CO2 and indoor climate levels were both rated as “Excellent”, but VOC levels were simply “Fine”, then the overall IAQI rating would be “Fine”.
Carbon dioxide (CO2)
Research has found that indoor levels of carbon dioxide have a negative impact on cognitive performance as well as human health. Average indoor CO2 concentrations range from 600-1000 ppm, but can exceed 2000 ppm with increased occupancies and poor ventilation.
Exposure to >1000 ppm leads to decreased cognitive abilities, while levels >2000 ppm have been linked to inflammation, kidney calcification, bone demineralization, oxidative stress, and endothelial dysfunction.
Hence, we have developed the following AQI specific to carbon dioxide based on real-time values:
| Rating | Index | CO2 ppm | Meaning |
|---|---|---|---|
| Excellent | 1 | 0 - 400 | The air inside is as fresh as the air outside. |
| Fine | 2 | 400 - 1000 | The air quality inside remains at harmless levels. |
| Moderate | 3 | 1000 - 1500 | The air quality inside has reached conspicuous levels. |
| Poor | 4 | 1500 - 2000 | The air quality inside has reached precarious levels. |
| Very Poor | 5 | 2000 - 5000 | The air quality inside has reached unacceptable levels. |
| Severe | 6 | from 5000 | The air quality inside has exceeded maximum workplace concentration values. |
Indoor Climate: Temperature (T) and Relative Humidity (RH)
We measure temperature and relative humidity because it is, first and foremost, an issue of comfort for the building’s occupants. Aside from this, high temperatures and humidity have been found to increase the concentrations of certain pollutants. In addition, regulating temperature and humidity levels minimize the risk of mould growth indoors, thus preventing illnesses like Sick Building Syndrome.
For our IAQI, the ratio of temperature and relative humidity is calculated and presented on a scale of 1-6 with a rating of Excellent to Severe. A rating higher than 3 requires action to be taken on either adjusting the temperature or the humidity of the building, so as to best minimize mould risk and air pollution while maximizing comfort.
| 90% | 6 | 5 | 4 | 3 | 3 | 3 | 3 | 4 | 5 | 5 | 6 | 6 | 6 |
| 80% | 5 | 4 | 2 | 2 | 2 | 2 | 2 | 3 | 4 | 5 | 5 | 5 | 6 |
| 70% | 5 | 4 | 3 | 2 | 1 | 1 | 1 | 2 | 3 | 4 | 5 | 5 | 6 |
| 60% | 5 | 4 | 3 | 2 | 1 | 1 | 1 | 2 | 2 | 3 | 4 | 5 | 6 |
| 50% | 5 | 5 | 4 | 3 | 2 | 1 | 1 | 1 | 2 | 3 | 4 | 5 | 6 |
| 40% | 6 | 5 | 5 | 4 | 3 | 3 | 3 | 2 | 2 | 3 | 4 | 5 | 6 |
| 30% | 6 | 5 | 5 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 5 | 6 |
| 20% | 6 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 6 |
| 10% | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| 0% / 15C | 16C | 17C | 18C | 19C | 20C | 21C | 22C | 23C | 24C | 25C | 26C | 27C | 28C |
Volatile Organic Compounds (VOCs)
Volatile organic compounds refer to a large group of carbon-containing substances including hydrocarbons, alcohols, aldehydes, and organic acids. They are particularly concentrated indoors due to internal sources from interior products and building materials such as furniture, plastics, carpets, wallpapers, cleaning materials, copy machines, lacquers, solvents, synthetic fragrances, insecticides and thirdhand tobacco smoke.
The indoor impact of VOCs has greater health implications since people spend time predominantly in buildings. This makes them an important air pollutant to monitor as they have toxic, mutagenic, carcinogenic, genotoxic, and teratogenic effects on humans. Milder symptoms are characterized by headaches, fatigue, loss of productivity, and sleep disorders, which are categorized as “Sick Building Syndrome”. More serious health effects include damage to the liver, kidney, and central nervous system, and cancers like leukemia and lymphoma.
Indoor organic pollutants have been categorized as volatile organic compounds (VOCs), very volatile organic compounds (VVOCs), and semi-volatile organic compounds (SVOCs). The sum of all the VOC concentration types combined becomes the total volatile organic compounds (TVOCs) value. Breeze Technologies’ real-time IAQI for TVOCs are presented as thus:
| Rating | Index |
|---|---|
| Excellent | 0 - 50 |
| Fine | 51 - 100 |
| Moderate | 101 - 150 |
| Poor | 151 - 200 |
| Very Poor | 201 - 300 |
| Severe | 301 - 500 |
Take control of the air quality in your building today
Breeze Technologies’ indoor air quality monitoring and management solutions can be deployed quickly with ease, with real-time results analyzed and presented on our Environmental Intelligence Cloud. We notify you immediately if an issue that requires your attention arises and provide the most efficient and effective interventions for your building. Contact us for further information and individual quotes, and make cleaner air a priority for your space today!
